Patent Publication Number: US-8975090-B2

Title: Method for manufacturing a MEMS sensor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a Continuation of U.S. application Ser. No. 13/952,214, filed on Jul. 26, 2013, which is a divisional of application Ser. No. 13/274,292, filed on Oct. 14, 2011, that claims the benefit of priority of Japanese applications 2010-212341 filed on Sep. 22, 2010, 2010-232910 filed on Oct. 15, 2010, 2010-271982 filed on Dec. 6, 2010, 2010-277213 filed on Dec. 13, 2010, and 2010-277214 filed on Dec. 13, 2010. The disclosures of these prior U.S. and Japanese applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for manufacturing a MEMS sensor. 
     2. Description of Related Arts 
     A MEMS (Micro Electro Mechanical Systems) sensor detects acceleration, an angular velocity, and a pressure, etc., applied to an object by using a “structure” that changes according to application of an external force. 
     As a detection method of a MEMS sensor, for example, a capacitance type that performs detection based on a change in capacitance of a capacitor is known. As detailed devices, capacitance type gyro sensors and capacitance type acceleration sensors, etc., are known. 
     SUMMARY OF THE INVENTION 
     A first object of the present invention is to provide a capacitance type gyro sensor that is downsized and has excellent detection sensitivity. 
     A second object of the present invention is to provide a capacitance type acceleration sensor that has a simple structure and excellent detection sensitivity. 
     A third object of the present invention is to provide a method for manufacturing a MEMS sensor in which a layer for protecting a fixed electrode and a movable electrode can be formed by a simple method at a low cost, and a MEMS sensor manufactured by this manufacturing method. 
     A fourth object of the present invention is to provide a highly reliable MEMS package that has a MEMS sensor including a protective layer for a fixed electrode and a movable electrode. 
     A fifth object of the present invention is to provide a MEMS sensor in which a lower electrode can be easily formed directly below an upper electrode via a cavity, the upper electrode and the lower electrode are prevented from being short-circuited by each other, and the detection accuracy of the sensor can be improved, and a method for manufacturing the same. 
     A sixth object of the present invention is to provide a MEMS package with a MEMS sensor having excellent detection accuracy. 
     A seventh object of the present invention is to provide a MEMS sensor in which the variation in size of a first electrode and a second electrode that have comb-tooth-like shapes and engage with each other can be reduced and the detection accuracy of the sensor can be improved, and a method for manufacturing the same. 
     The above-described or other objects, features, and effects of the present invention will be clarified by the following description of preferred embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a gyro sensor according to a first preferred embodiment of the present invention. 
         FIG. 2  is a schematic plan view of a sensor portion shown in  FIG. 1 . 
         FIG. 3  is a plan view of a principal portion of an X-axis sensor shown in  FIG. 2 . 
         FIG. 4  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 2 , illustrating a section taken along the cutting plane A-A in  FIG. 3 . 
         FIG. 5  is a plan view of a principal portion of a Z-axis sensor shown in  FIG. 2 . 
         FIG. 6  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 2 , illustrating a section taken along the cutting plane B-B in  FIG. 5 . 
         FIG. 7A  to  FIG. 7G  are sectional views showing parts of a manufacturing process of the gyro sensor according to the first preferred embodiment of the present invention in order of steps. 
         FIG. 8  is a view showing an exemplary variation of first drive portions and second drive portions shown in  FIG. 5 . 
         FIG. 9  is a schematic plan view of an acceleration sensor according to a second preferred embodiment of the present invention. 
         FIG. 10  is a schematic plan view of a sensor portion shown in  FIG. 9 . 
         FIG. 11  is a plan view of a principal portion of an X-axis sensor shown in  FIG. 10 . 
         FIG. 12  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 10 , illustrating a section taken along the cutting plane C-C in  FIG. 11 . 
         FIG. 13  is a plan view of a principal portion of a Z-axis sensor shown in  FIG. 10 . 
         FIG. 14  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 10 , illustrating a section taken along the cutting plane D-D in  FIG. 13 . 
         FIG. 15A  to  FIG. 15G  are sectional views showing parts of a manufacturing process of the acceleration sensor according to the second preferred embodiment of the present invention in order of steps. 
         FIG. 16  is a view showing an exemplary variation of a Z movable electrode shown in  FIG. 14 . 
         FIG. 17  is a view showing an exemplary variation of dielectric layers shown in  FIG. 14 . 
         FIG. 18  is a view showing an exemplary variation of the dielectric layers shown in  FIG. 16 . 
         FIG. 19  is a schematic perspective view of a MEMS package according to a third preferred embodiment of the present invention. 
         FIG. 20  is a sectional view of a principal portion of the MEMS package shown in  FIG. 19 , illustrating a section taken along the cutting plane E-E in  FIG. 19 . 
         FIG. 21  is a schematic plan view of an acceleration sensor shown in  FIG. 19 . 
         FIG. 22  is a plan view of a principal portion of an X-axis sensor shown in  FIG. 21 . 
         FIG. 23  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 21 , illustrating a section taken along the cutting plane F-F in  FIG. 22 . 
         FIG. 24  is a plan view of a principal portion of a Z-axis sensor shown in  FIG. 21 . 
         FIG. 25  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 21 , illustrating a section taken along the cutting plane G-G in  FIG. 24 . 
         FIG. 26A  to  FIG. 26M  are sectional views showing parts of a manufacturing process of the Z-axis sensors shown in  FIG. 21  in order of steps. 
         FIG. 27  is a plan view showing a mode in which the Z-axis sensor shown in  FIG. 24  is used as an angular velocity sensor. 
         FIG. 28  is a schematic perspective view of a MEMS package according to a fourth preferred embodiment of the present invention. 
         FIG. 29  is a schematic sectional view of the Z-axis sensor shown in  FIG. 1 . 
         FIG. 30A  to  FIG. 30L  are sectional views showing parts of a manufacturing process of the Z-axis sensors shown in  FIG. 29  in order of steps. 
         FIG. 31  is a plan view showing a mode in which the Z-axis sensor shown in  FIG. 29  is used as an acceleration sensor. 
         FIG. 32  is a view showing an exemplary variation of the Z-axis sensor shown in  FIG. 29 . 
         FIG. 33  is a schematic perspective view of a MEMS package according to a fifth preferred embodiment of the present invention. 
         FIG. 34  is a schematic plan view of the angular velocity sensor shown in  FIG. 1 . 
         FIG. 35  is a plan view of a principal portion of the X-axis sensor shown in  FIG. 2 . 
         FIG. 36  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 2 , illustrating a section taken along the cutting plane H-H in  FIG. 35 . 
         FIG. 37  is a plan view of a principal portion of the Z-axis sensor shown in  FIG. 34 . 
         FIG. 38  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 34 , illustrating a section taken along the cutting plane I-I shown in  FIG. 37 . 
         FIG. 39A  to  FIG. 39K  are sectional views showing parts of a manufacturing process of the Z-axis sensors shown in  FIG. 34  in order of steps. 
         FIG. 40  is a plan view showing a mode in which the Z-axis sensor shown in  FIG. 37  is used as an acceleration sensor. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A capacitance type gyro sensor according to an aspect of the present invention includes a semiconductor substrate having a cavity inside by forming an upper wall and a bottom wall, and having a surface portion forming the upper wall of the cavity and a back surface portion forming the bottom wall, a first electrode formed by processing the surface portion of the semiconductor substrate, and integrally having a first base portion and first comb tooth portions extending from the first base portion and aligned at intervals like comb teeth, and a second electrode formed by processing the surface portion of the semiconductor substrate, and integrally having a second base portion and second comb tooth portions extending from the second base portion toward the portions between the first comb tooth portions and aligned like comb teeth to engage with the first comb tooth portions at an interval, and drives the first electrode or the second electrode up and down with respect to the other electrode and detects an angular velocity applied at the time of this driving by detecting a change in capacitance between the first comb tooth portion and the second comb tooth portion, wherein the first electrode includes first drive portions extending from opposed portions opposed to the second comb tooth portions of the first base portion toward the second comb tooth portions, and electrically insulated from other portions of the first base portion, and the second electrode includes second drive portions formed on the tip end portions of the second comb tooth portions opposed to the first drive portions so as to be electrically insulated from other portions of the second comb tooth portions, and the first drive portions and the second drive portions engage with each other at an interval like comb teeth. 
     In the capacitance type gyro sensor according to an aspect of the present invention, the first electrode integrally includes a first base portion and a comb-tooth-like electrode (an assembly of a plurality of first comb tooth portions) supported on this first base portion. The first comb tooth portions engage with the comb-tooth-like second electrode (assembly of the plurality of second comb tooth portions) at an interval. Accordingly, the first comb tooth portions and the second comb tooth portions constitute electrodes of a capacitor (detector) when a fixed voltage is applied between the first comb tooth portions and the second comb tooth portions and which changes in capacitance due to a change in interval between these and/or a change in opposing area. 
     On the other hand, on the first base portion of the first electrode, first drive portions extending toward the second comb tooth portions disposed between the first comb tooth portions adjacent to each other are provided. Second drive portions are provided on tip end portions of the second comb tooth portions facing the first drive portions, and the first drive portions and the second drive portions engage with each other like comb teeth. Accordingly, the first drive portions and the second drive portions drive either the first electrode or the second electrode by coulomb forces generated by changes in drive voltages when the drive voltages are applied between these electrodes. 
     In this capacitance type gyro sensor, the first comb tooth portions and the second comb tooth portions for detecting an angular velocity and the first drive portions and the second drive portions for driving the first electrode and the second electrode are all formed by processing the surface portion of the semiconductor substrate. Therefore, the thickness of the whole sensor is substantially the thickness of the substrate, so that the sensor can be downsized. 
     Next, as an example of angular velocity detection by using this capacitance type gyro sensor, assuming a three-dimensional orthogonal XYZ coordinate system indicating the thickness direction of the semiconductor substrate in the Z-axis direction, detection of an angular velocity applied around the X-axis when the first electrode is driven in the Z-axis direction will be described. 
     First, between the first drive portions and the second drive portions that engage with each other like comb teeth, drive voltages with the same polarity and drive voltages with different polarities are alternately applied. Accordingly, between the first drive portions and the second drive portions, coulomb repulsive and attractive forces are alternately generated. As a result, the first comb tooth portions integrated with the first drive portions oscillate (are driven) up and down (along the thickness direction of the semiconductor substrate) along the Z-axis direction like a pendulum around the second comb tooth portions as a center of oscillation. At this time, the first drive portions and the second drive portions as drive electrodes for driving the first electrode are disposed to engage with each other like comb teeth, so that the opposing area between these can be made larger than in the case where one drive electrode and the other drive electrode are just opposed to each other or just adjacent to each other. Therefore, the first electrode can be oscillated with a large amplitude, so that the detection sensitivity can be improved. 
     Then, in this state, when an angular velocity to rotate the first electrode around the X axis as a central axis is applied to the first electrode being oscillated, a coriolis force is generated to the first electrode in the Y-axis direction. This coriolis force changes the distance between the first comb tooth portions (first electrode) and the second comb tooth portions (second electrode) (electrode-to-electrode distance) and/or the opposing area. Then, by detecting a change in capacitance between the movable electrode and the fixed electrode caused by this change in electrode-to-electrode distance and/or opposing area, the angular velocity around the X-axis can be detected. 
     The capacitance type gyro sensor according to the present invention may further include first insulating layers that are embedded in the first base portion so as to surround the opposed portions and insulate and separate the opposed portions from other portions of the first base portion. The capacitance type gyro sensor according to the present invention may further include second insulating layers that are embedded in the base end portion sides relative to the tip end portions of the second comb tooth portions and insulate and separate the tip end portions from other portions of the second comb tooth portions. 
     When the first insulating layers and/or the second insulating layers are embedded in the semiconductor substrate, the surface of the semiconductor substrate can be efficiently used as a space for leading wirings to be connected to the first electrode and the second electrode. 
     In the capacitance type gyro sensor according to the present invention, the semiconductor substrate may be a conductive silicon substrate. 
     When the semiconductor substrate is a conductive silicon substrate, without applying a special treatment for giving conductivity to the first electrode and the second electrode molded to have predetermined shapes, the molded structures can be used as they are as electrodes. Portions except for the portions to be used as electrodes can be used as wirings. 
     A capacitance type gyro sensor according to another aspect of the present invention includes a semiconductor substrate having a cavity inside by forming an upper wall and a bottom wall, and having a surface portion forming the upper wall of the cavity and a back surface portion forming the bottom wall, a first electrode formed by processing the surface portion of the semiconductor substrate, and integrally having a first base portion and first comb tooth portions extending from the first base portion and aligned at intervals like comb teeth, a second electrode formed by processing the surface portion of the semiconductor substrate, and integrally having a second base portion and second comb tooth portions extending from the second base portion toward the portions between the first comb tooth portions and aligned like comb teeth to engage with the first comb tooth portions at an interval, a first contact wiring that is formed on the surface portion of the semiconductor substrate and comes into direct contact with the first electrode from the surface side, and a second contact wiring that is formed on the surface portion of the semiconductor substrate, and comes into direct contact with the second electrode from the surface side, wherein the first electrode includes first drive portions extending from opposed portions opposed to the second comb tooth portions of the first base portion toward the second comb tooth portions, and the second electrode includes second drive portions formed on the tip end portions of the second comb tooth portions opposed to the first drive portions so as to be electrically insulated from other portions of the second comb tooth portions, and the first drive portions and the second drive portions engage with each other at an interval like comb teeth. 
     In the capacitance type gyro sensor according to another aspect of the present invention, the first drive portions may be electrically insulated from other portions of the first base portion, and in this case, the capacitance type gyro sensor may further include first insulating layers that are embedded in the first base portion so as to surround the opposed portions and insulate and separate the opposed portions from other portions of the first base portion. 
     The capacitance type gyro sensor according to another aspect of the present invention may further include second insulating layers that are embedded in the base end portion sides relative to the tip end portions of the second comb tooth portions and insulate and separate the tip end portions from other portions of the second comb tooth portions. 
     In the capacitance type gyro sensor according to another aspect of the present invention, the first contact wiring may include first detection wiring that comes into contact with the first comb tooth portions, the second contact wiring may include second detection wiring that comes into contact with the base end portion sides relative to the second insulating layers of the second comb tooth portions, and the first electrode or the second electrode is driven relative to the other electrode, and an angular velocity applied at the time of this driving may be detected by detecting a change in capacitance between the first comb tooth portions and the second comb tooth portions. 
     In this case, by the first detection wiring and the second detection wiring, an electric signal corresponding to a change in capacitance caused by the distance between the first comb tooth portions (first electrode) and the second comb tooth portions (second electrode) (electrode-to-electrode distance) and/or the opposing area can be detected. 
     A capacitance type acceleration sensor according to an aspect of the present invention includes a semiconductor substrate having a cavity inside by forming an upper wall and a bottom wall, and having a surface portion forming the upper wall of the cavity and a back surface portion forming the bottom wall, and a first electrode and a second electrode that are formed by processing the surface portion of the semiconductor substrate and have comb-tooth-like shapes to engage with each other at an interval, and detects acceleration when the first electrode or the second electrode moves up and down with respect to the other electrode by detecting a change in capacitance between the first electrode and the second electrode, wherein the first electrode includes dielectric layers that have a predetermined thickness from the surface or the back surface to a halfway point of the first electrode along the thickness direction orthogonal to the opposing direction of the second electrode and has a predetermined width along the opposing direction, and conductive layers consisting of remaining portions except for the dielectric layers. 
     With the present arrangement, the capacitor for detecting acceleration is formed by making the first electrode and the second electrode opposed to each other. The capacitor detects acceleration based on a change in capacitance caused by oscillation of the first electrode or the second electrode. 
     In this capacitor, the first electrode is partially formed of dielectric layers having a predetermined thickness along the thickness direction orthogonal to an opposing direction of the first electrode and the second electrode and a predetermined width along the opposing direction. 
     Accordingly, in this capacitor, at a portion in which the dielectric layer and the second electrode are opposed to each other, the electrode-to-electrode distance d1 of the capacitor is increased by the width W of the dielectric layer as compared with the electrode-to-electrode distance d2 (distance between the first electrode and the second electrode) that the capacitor originally has (that is, d1=d2+W). Therefore, a capacitance difference can be provided in one capacitor. 
     For example, a method for detecting acceleration when the first electrode is a movable electrode that oscillates along the Z-axis direction and dielectric layers are embedded from the surface to a halfway point of the movable electrode (first electrode) will be described. 
     When acceleration in the Z-axis direction is applied to the sensor, the comb-tooth-like first electrode (movable electrode) oscillates up and down like a pendulum as a center of oscillation along the Z-axis direction with respect to the second electrode similarly around the comb-tooth-like second electrode (fixed electrode). 
     At this time, when the first electrode oscillates first to the side (upper side) away from the cavity with respect to the second electrode, the capacitance of the capacitor decreases at a decrease rate D1 (D1≧0) based on the electrode-to-electrode distance d1 while the dielectric layers are opposed to the second electrode. Thereafter, when the dielectric layers completely protrude above the second electrode and only the conductive layers are opposed to the second electrode, the capacitance decreases from this timing at a decrease rate D2 (D2≧0) based on the original electrode-to-electrode distance d2. This decrease rate D2 of the capacitance is higher than the decrease rate D1 because the electrode-to-electrode distance d2 is smaller than the electrode-to-electrode distance d1 and the capacitance to decrease per unit time increases. Specifically, when the first electrode starts to oscillate to the upper side, the capacitance of the capacitor decreases at the first decrease rate D1 and then decreases at the second decrease rate D2 higher than the first decrease rate D1. 
     On the other hand, when the first electrode oscillates first to the side (the lower side) to approach the cavity with respect to the second electrode, until portions of the dielectric layers start to protrude to the side below the second electrode, the capacitance of the capacitor decreases at the decrease rate D2 based on the electrode-to-electrode distance d2. Thereafter, when portions of the dielectric layers start to protrude below the second electrode, the capacitance decreases from this timing at the decrease rate D1 based on the electrode-to-electrode distance d1. This decrease rate D1 of the capacitance is smaller than the decrease rate D2 because the electrode-to-electrode distance d1 is larger than the electrode-to-electrode distance d2 and the capacitance to decrease per unit time becomes smaller. Specifically, when the first electrode starts to oscillate to the lower side, the capacitance of the capacitor decreases at the second decrease rate D2 and then decreases at the first decrease rate D1 smaller than the second decrease rate D2. 
     Therefore, by detecting whether the capacitance of the capacitor decreases at the relatively small decrease rate D1 and then decreases at the relatively large decrease rate D2 (D1→D2) or decreases at the relatively large decrease rate D2 and then decreases at the relatively small decrease rate D1 (D2→D1), the direction in which the first electrode oscillated first (the direction away from the cavity or the direction approaching the cavity) can be easily grasped. As a result, the direction of the acceleration vector can be accurately detected, so that the detection sensitivity can be improved. 
     In addition, this improvement in detection sensitivity is obtained by embedding the dielectric layers in the first electrode constituting the capacitor, so that the sensor structure can be prevented from becoming complicated. 
     In the capacitance type acceleration sensor according to an aspect of the present invention, it is preferable that the dielectric layers are one-sided to one end side in the width direction of the first electrode, and the conductive layer includes a first portion formed adjacently on the other end side in the width direction to the dielectric layer, and a second portion formed below the dielectric layer and having a width larger than that of the first portion. 
     With the present arrangement, the conductive layers are formed across the entire region in the thickness direction from the surface to the back surface of the first electrode. 
     Therefore, for example, when the first electrode is a movable electrode that oscillates along the Z-axis direction as described above, regardless of the direction of oscillation (upward or downward) of the first electrode with respect to the second electrode, the opposing area of the conductive layer of the first electrode and the second electrode decreases by necessity. In detail, when the first electrode oscillates to the upper side first, the opposing area of the first portion of the conductive layer and the second electrode decreases, and on the other hand, when the first electrode oscillates to the lower side first, the opposing area of the second portion of the conductive layer and the second electrode decreases. Specifically, this arrangement shows the case of D1&gt;0 and D2&gt;0 in the above-described detection method. 
     Accordingly, a change in capacitance can be detected immediately after the first electrode starts to oscillate, so that the magnitude of the acceleration vector immediately after the start of oscillation can also be detected. 
     In the capacitance type acceleration sensor according to an aspect of the present invention, it is preferable that the dielectric layers are formed from one end to the other end in the width direction of the first electrode and have the same width as that of the first electrode, and the first electrode has a lamination structure including the dielectric layers and the conductive layers formed below the dielectric layers. 
     With the present arrangement, the portion from the surface or the back surface to a halfway point of the first electrode is entirely formed of the dielectric layer. In this case, in the portion in which the dielectric layer and the second electrode are opposed to each other, the conductive layer opposed to the second electrode does not exist, so that the capacitance becomes 0 (zero). 
     Therefore, for example, in the case where the first electrode is a movable electrode that oscillates along the Z-axis direction as described above, when the first electrode oscillates to the upper side first, the capacitance of the capacitor does not change (that is, D1=0) while the dielectric layers are opposed to the second electrode. Thereafter, when the dielectric layers completely protrude above the second electrode and only the conductive layers are opposed to the second electrode, the capacitance decreases from this timing at the decrease rate D2 (D2&gt;0) based on the original electrode-to-electrode distance d2. 
     On the other hand, when the first electrode oscillates to the lower side first, the capacitance of the capacitor decreases at the decrease rate D2 (D&gt;0) based on the electrode-to-electrode distance d2 until the dielectric layers start to protrude below the second electrode. Thereafter, when the dielectric layers start to protrude below the second electrode, the capacitance from this timing does not change (that is, D1=0). 
     Therefore, with this arrangement, the direction of the acceleration vector can be judged based on whether the decrease rate of the capacitance is 0 or not, that is, based on whether or not the capacitance changes. Therefore, acceleration can be easily detected. 
     It is also possible that the first electrode is a movable electrode and the second electrode is a fixed electrode. Alternatively, it is also possible that the first electrode is a fixed electrode and the second electrode is a movable electrode. 
     In the capacitance type acceleration sensor according to an aspect of the present invention, the semiconductor substrate is preferably a conductive silicon substrate. 
     When the semiconductor substrate is a conductive silicon substrate, even without applying a special treatment for giving conductivity to the first electrode and the second electrode molded to have predetermined shapes, the molded structures can be used as they are as electrodes. The portions except for the portions to be used as electrodes can be used as wirings. 
     A method for manufacturing a MEMS sensor according to an aspect of the present invention includes the steps of forming a recess dug to a halfway point in the thickness direction of a semiconductor substrate by selectively etching the surface layer portion of a sensor region of the semiconductor substrate having the sensor region and a peripheral region surrounding the sensor region, and concurrently, forming comb-tooth-like fixed electrode and movable electrode that engage with each other via the recess, forming a sacrifice layer that covers the sensor region and exposes the peripheral region, forming a protective layer made of a first inorganic material on the semiconductor substrate so that the peripheral edge portion of the protective layer is bonded to the peripheral region and the central portion surrounded by the peripheral edge portion covers the sacrifice layer, forming a space between the protective layer and the sensor region by removing the sacrifice layer directly below the protective layer, and forming a cavity by linking the lower portions of the fixed electrode and the movable electrode to each other by isotropic etching by supplying an etching medium into the recess after removing the sacrifice layer. 
     According to this method, by forming a layer made of a first inorganic material on the semiconductor substrate in which the fixed electrode and the movable electrode are formed, even without using a bonding material such as glass frit, the layer for protecting the fixed electrode and the movable electrode can be formed. Therefore, the cost required to form the protective layer can be reduced. 
     Concerning workability of formation of the protective layer, the operation can be made simpler than in the case where a lid substrate is bonded by using a bonding material. 
     In detail, according to this method, a sacrifice layer is formed to cover the sensor region in which the fixed electrode and the movable electrode are formed, a protective layer is formed to cover the sacrifice layer, and then, the sacrifice layer directly below the protective layer is removed. Accordingly, a space is formed in the portion in which the sacrifice layer existed, and a protective layer covering the fixed electrode and the movable electrode is formed on the sensor region via the space. Therefore, without performing an operation such as position alignment of wafers, the protective layer can be easily formed by combining known semiconductor device manufacturing techniques (for example, a CVD (Chemical Vapor Deposition) method, sputtering, and photolithography, etc.). In addition, when forming the sacrifice layer for forming the space between the sensor region and the protective layer, no cavity is formed directly below the fixed electrode and the movable electrode, and the lower portions of these electrodes are fixed integrally to the semiconductor substrate. Therefore, even if the sacrifice layer comes into contact with the fixed electrode and the movable electrode, the electrodes do not oscillate due to the impact of this contact. Therefore, it is not necessary to add a step for protecting the electrodes from the sacrifice layer, etc., so that the process can be prevented from becoming complicated. 
     In the method for manufacturing a MEMS sensor according to an aspect of the present invention, the step of forming the sacrifice layer preferably includes a step of forming a first sacrifice layer made of a second inorganic material different from the material of the protective layer so as to close the opening end of the recess formed in the sensor region, and after forming the first sacrifice layer, a step of forming a second sacrifice layer made of a metal material on the first sacrifice layer so as to cover the sensor region. 
     According to this method, the sensor region is covered by the second sacrifice layer, so that the space between the protective layer and the sensor region is formed by removing (etching) the second sacrifice layer. Specifically, what (the second sacrifice layer) is to be removed by etching is made of the metal material, and what (the protective layer) is to be left even after etching is made of the first inorganic material. Accordingly, when forming the space, the etching selectivity of the protective layer to the sacrifice layer (the second sacrifice layer) can be increased. Therefore, even if the protective layer is exposed to an etching medium to be used for removing the second sacrifice layer for a long period of time, the etching medium is for etching metal materials, so that erosion of the protective layer made of the first inorganic material can be reduced. Therefore, the shape of the protective layer can be excellently maintained. 
     On the other hand, as a sacrifice layer that closes the opening end of the recess, when the second sacrifice layer made of a metal material is used, if the second sacrifice layer remains on the fixed electrode and/or the movable electrode, an operation failure of the sensor may occur by the second sacrifice layer. For example, if the second sacrifice layer remains across the fixed electrode and the movable electrode, a short-circuit occurs between the fixed electrode and the movable electrode via this second sacrifice layer. 
     Therefore, as a sacrifice layer that closes the opening end of the recess, the first sacrifice layer made of the second inorganic material is used. Accordingly, while etching selectivity of the protective layer to the first sacrifice layer is secured, the operation failure of the sensor can be prevented from occurring due to the sacrifice layer remaining. 
     The description that the protective layer has etching selectivity to the sacrifice layer means that, for example, the materials of these layers satisfy a ratio (etching selectivity) of the etching rate of the sacrifice layer with a certain etching medium to the etching rate of the protective layer with this etching medium=(etching rate of protective layer/etching rate of sacrifice layer)≠1. 
     The first sacrifice layer and the second sacrifice layer may be made of an inorganic material that can be etched with a fluorine-based gas and a metal material that can be etched with a chlorine-based gas, respectively. 
     In detail, when the protective layer is made of SiO 2 , it is preferable that the first sacrifice layer is made of SiN, and the second sacrifice layer is made of Al. 
     The method for manufacturing a MEMS sensor according to an aspect of the present invention preferably further includes a step of forming a protective film having etching selectivity to the sacrifice layer so as to cover side walls of the fixed electrode and the movable electrode previous to formation of the sacrifice layer. 
     According to this method, the side walls of the fixed electrode and the movable electrode are covered by the protective film having etching selectivity to the sacrifice layer. Therefore, when removing the sacrifice layer by etching, even if the etching medium comes into contact with the side walls of the fixed electrode and the movable electrode, erosion (damage) of the fixed electrode and the movable electrode can be reduced. As a result, the variation in size of the fixed electrode and the movable electrode can be reduced. 
     The step of removing the sacrifice layer may include a step of supplying an etching medium capable of etching the sacrifice layer from a through hole by forming the through hole in the central portion of the protective layer. 
     A MEMS sensor according to an aspect of the present invention includes a semiconductor substrate having a sensor region and a peripheral region surrounding the sensor region and having a cavity formed directly below a surface layer portion of the sensor region, comb-tooth-like fixed electrode and movable electrode that are formed by processing the surface layer portion of the sensor region and engage with each other at an interval, and a protective layer that has a peripheral edge portion bonded to the peripheral region of the semiconductor substrate and a central portion surrounded by the peripheral edge portion and covering the fixed electrode and the movable electrode while being spaced from the sensor region and is made of a first inorganic material. 
     With the present arrangement, the fixed electrode and the movable electrode are covered by the central portion of the protective layer. Accordingly, dust, etc., can be prevented from entering the inside of the protective layer from the outside of the protective layer (the side opposite to the sensor region with respect to the protective layer). Therefore, the fixed electrode and the movable electrode can be excellently protected from dust, etc. As a result, operation failures of the sensor can be reduced. 
     In the MEMS sensor according to an aspect of the present invention, it is preferable that when the peripheral region includes a pad region in which electrode pads electrically connected to the fixed electrode and the movable electrode are formed, openings for exposing the electrode pads are formed in the peripheral edge portion of the protective layer. 
     In the central portion of the protective layer, a through hole that makes communication between the inside and the outside of the protective layer may be formed. 
     The MEMS sensor according to an aspect of the present invention may further include first insulating layers that are selectively embedded in the fixed electrode and insulate and separate certain portions of the fixed electrode from other portions of the fixed electrode. Further, the MEMS sensor according to an aspect of the present invention may further include second insulating layers that are selectively embedded in the movable electrode and insulate and separate certain portions of the movable electrode from other portions of the movable electrode. 
     The protective layer may be made of SiO 2  or SiN. 
     In the MEMS sensor according to an aspect of the present invention, the semiconductor substrate is preferably a conductive silicon substrate. 
     When the semiconductor substrate is a conductive silicon substrate, even without applying a special treatment for giving conductivity to the fixed electrode and movable electrode molded to have predetermined shapes, the molded structures can be used as they are as electrodes. Portions except for the portions to be used as electrodes can be used as wirings. 
     The MEMS sensor according to an aspect of the present invention may include an acceleration sensor that detects acceleration applied to the MEMS sensor by detecting a change in capacitance between the fixed electrode and the movable electrode. 
     The MEMS sensor according to an aspect of the present invention may include an angular velocity sensor that drives the movable electrode in directions approaching and away from the cavity and detects an angular velocity applied to the MEMS sensor at the time of this driving by detecting a change in capacitance between the movable electrode and the fixed electrode. 
     A MEMS package according to an aspect of the present invention includes the MEMS sensor and a resin package formed to cover the MEMS sensor. 
     With the present arrangement, the MEMS sensor according to an aspect of the present invention is used. Therefore, in the MEMS sensor, dust, etc., can be prevented from entering the inside of the protective layer from the outside, so that operation failures of the sensor can be reduced. As a result, a MEMS package with a highly reliable MEMS sensor can be provided. 
     The MEMS package according to an aspect of the present invention may further include an integrated circuit that is electrically connected to the MEMS sensor and covered together with the MEMS sensor by the same resin package. When the MEMS package according to an aspect of the present invention further includes a substrate that has a surface and a back surface and supports the MEMS sensor by the surface, the resin package may seal the MEMS sensor so as to cover the surface of the substrate and expose the back surface of the substrate. 
     A method for manufacturing a MEMS sensor according to another aspect of the present invention includes the steps of selectively forming a lower electrode on a semiconductor substrate, laminating an electrode coating film made of a material having etching selectivity to polysilicon on the semiconductor substrate so as to coat the lower electrode, selectively forming a sacrifice polysilicon layer on the electrode coating film, laminating a sacrifice oxide film on the electrode coating film so as to coat the sacrifice polysilicon layer, forming an electrode polysilicon layer on the sacrifice oxide film, forming an upper electrode by selectively etching the electrode polysilicon layer, forming a protective film having etching selectivity to polysilicon so as to cover side walls of the upper electrode, exposing the sacrifice polysilicon layer by removing portions of the sacrifice oxide film, and forming a cavity directly below the upper electrode by removing the exposed sacrifice polysilicon layer. 
     According to this method, after a lower electrode is formed on a semiconductor substrate, an upper electrode is formed on the semiconductor substrate by using an electrode polysilicon layer. Therefore, before the upper electrode is formed, the lower electrode can be easily formed directly below the upper electrode. Further, a sacrifice polysilicon layer is formed between the lower electrode and the electrode polysilicon layer, and after the upper electrode is formed, the sacrifice polysilicon layer is removed. Therefore, a cavity can be easily formed between the upper electrode and the lower electrode. Accordingly, a MEMS sensor including a capacitor consisting of an upper electrode and a lower electrode opposed vertically to each other via a cavity can be manufactured. 
     This MEMS sensor includes, for example, a semiconductor substrate, a lower electrode selectively formed on the semiconductor substrate, an electrode coating film made of an insulating material and formed on the semiconductor substrate so as to coat the lower electrode, and a polysilicon layer having an upper electrode formed at an interval above the electrode coating film and opposed to the lower electrode via the electrode coating film. 
     With the present arrangement, the lower electrode is formed along the surface of the semiconductor substrate. Therefore, by adjusting the area of the lower electrode, the capacitance of the capacitor consisting of the upper electrode and the lower electrode can be controlled to the optimum capacitance for sensor operations. 
     In addition, even after the cavity is formed by removing the sacrifice polysilicon layer, the lower electrode is covered by the electrode coating film. Therefore, even if the upper electrode approaches the lower electrode, the upper electrode and the lower electrode can be prevented from coming into contact with each other. As a result, the upper electrode and the lower electrode can be prevented from being short-circuited by each other. Therefore, operation failures of the sensor can be reduced. 
     As a result, with the MEMS sensor according to another aspect of the present invention, the detection accuracy of the sensor can be improved. 
     In the method for manufacturing a MEMS sensor according to another aspect of the present invention, the step of forming the upper electrode preferably includes a step of molding the electrode polysilicon layer into comb-tooth-like fixed electrode and movable electrode that engage with each other at an interval. 
     By this method, the MEMS sensor according to another aspect of the present invention in which the upper electrode includes comb-tooth-like fixed electrode and movable electrode that engage with each other at an interval can be manufactured. 
     In this MEMS sensor, the capacitor consisting of the fixed electrode and the movable electrode can be used for sensor operations. Accordingly, the capacitor relating to the detection operations of the sensor can be increased, so that the detection accuracy of the sensor can be further improved. 
     The method for manufacturing a MEMS sensor according to another aspect of the present invention preferably further includes a step of removing the protective film from the side walls of the fixed electrode and the movable electrode after removing the sacrifice polysilicon layer. 
     In the manufactured MEMS sensor, if the protective film remains on the side walls of the fixed electrode and the movable electrode, the fixed electrode and the movable electrode are easily electrically charged as compared with a case where no protective film remains. Therefore, for example, when a voltage X (V) is applied between the fixed electrode and the movable electrode, the sensor may erroneously recognize a potential difference between the fixed electrode and the movable electrode caused by electric charging as a voltage applied between the fixed electrode and the movable electrode, that is, a so-called memory effect may occur. As a result, a voltage smaller than the voltage X (V) may be applied between the fixed electrode and the movable electrode and the designed detection performance may not be realized. 
     Therefore, in the MEMS sensor manufactured by this method, the side walls of the fixed electrode and the movable electrode are exposed. Therefore, occurrence of the above-described memory effect can be reduced. As a result, a necessary and sufficient voltage can be applied between the fixed electrode and the movable electrode, and the designed detection performance can be reliably realized. 
     Preferably, the method for manufacturing a MEMS sensor according to another aspect of the present invention further includes a step of forming an opening that penetrates through the electrode coating film and selectively exposes the lower electrode previous to formation of the electrode polysilicon layer, and the step of forming the electrode polysilicon layer includes a step of forming the electrode polysilicon layer on the sacrifice oxide film and concurrently, making a portion of the electrode polysilicon layer enter the opening of the electrode coating film and come into contact with the lower electrode, and the step of forming the upper electrode includes a step of forming a contact electrode that is separated from the upper electrode and in contact with the lower electrode. 
     By this method, the MEMS sensor according to another aspect of the present invention in which the polysilicon layer further includes a contact electrode that penetrates through the electrode coating film and is in contact with the lower electrode can be manufactured. 
     In this MEMS sensor, by using a portion of the electrode polysilicon layer forming the upper electrode, a contact electrode is formed in the same layer as that of the upper electrode. Therefore, the contacts with the upper electrode and the lower electrode can be collectively formed in the same layer (polysilicon layer). 
     As a result, for example, when a wiring is formed on the contact electrode, the contact wiring for the upper electrode can be formed in the same step. As a result, the number of manufacturing steps can be reduced and the cost can be reduced. 
     By this manufacturing method, the MEMS sensor according to another aspect of the present invention further including a wiring on the contact electrode can be manufactured. 
     The step of forming a wiring on the contact electrode may include a step of forming a wiring on the upper electrode as well, concurrently. 
     The MEMS sensor according to another aspect of the present invention may include an acceleration sensor that detects acceleration applied to the MEMS sensor by detecting a change in capacitance between the lower electrode and the movable electrode. 
     With the present arrangement, acceleration can be detected by a plurality of capacitors including a capacitor consisting of the lower electrode and the movable electrode and a capacitor consisting of the fixed electrode and the movable electrode. Therefore, the acceleration applied to the sensor can be accurately detected. 
     The MEMS sensor according to another aspect of the present invention may include an angular velocity sensor that drives the movable electrode in directions approaching and away from the lower electrode, and detects an angular velocity applied to the MEMS sensor at the time of this driving by detecting a change in capacitance between the movable electrode and the fixed electrode. 
     With the present arrangement, by adjusting the area of the lower electrode, the area of the lower electrode with respect to the movable electrode can be made larger than the area of the fixed electrode with respect to the movable electrode. Therefore, as compared with the case where a drive voltage is applied between the fixed electrode and the movable electrode that engage with each other like comb teeth, the movable electrode can be oscillated with a large amplitude. As a result, the angular velocity detection sensitivity can be improved. 
     In the MEMS sensor according to another aspect of the present invention, it is preferable that the lower electrode is formed along a direction across the comb teeth of the movable electrode so as to be opposed to the entire comb-tooth-like movable electrode. 
     With the present arrangement, the lower electrode can be opposed with a large area to the movable electrode, so that the capacitance of the capacitor between the lower electrode and the movable electrode can be increased. As a result, the detection accuracy of the sensor can be improved. 
     The electrode coating film may be made of SiO 2 . The side walls of the upper electrode may be covered by a protective thin film made of an insulating material. 
     A MEMS package according to another aspect of the present invention includes the MEMS sensor according to another aspect of the present invention and a resin package formed to cover the MEMS sensor. 
     With the present arrangement, the MEMS sensor according to another aspect of the present invention is used. Therefore, in the MEMS sensor, the capacitance of the capacitor consisting of the upper electrode and the lower electrode can be controlled to an optimum capacitance for sensor operations, and the upper electrode and the lower electrode can be prevented from being short-circuited by each other. As a result, a MEMS package with a MEMS sensor having excellent detection accuracy can be provided. 
     The MEMS package according to another aspect of the present invention may further include an integrated circuit electrically connected to the MEMS sensor and covered together with the MEMS sensor by the same resin package. When the MEMS package according to another aspect of the present invention further includes a substrate that has a surface and a back surface and supports the MEMS sensor by the surface, the resin package may seal the MEMS sensor so as to cover the surface of the substrate and expose the back surface of the substrate. 
     A method for manufacturing a MEMS sensor according to still another aspect of the present invention includes the steps of forming a base film made of a material having etching selectivity to Si on a Si substrate, forming a polysilicon layer on the base film, forming trenches from the surface of the polysilicon layer to the surface of the Si substrate by selectively etching the polysilicon layer and the base film and concurrently, forming comb-tooth-like first electrode and second electrode that have a lamination structure including the base film and the polysilicon layer and engage with each other via the trenches, and forming a cavity directly below the base film by etching portions directly below the base film of the Si substrate by isotropic etching by supplying an etching medium into the trenches. 
     According to this method, the lowest layers of the first electrode and the second electrode are formed of the base film having etching selectivity to Si. Therefore, when a cavity is formed by isotropic etching of the Si substrate, even if the etching medium comes into contact with the first electrode and the second electrode, erosion of the first electrode and the second electrode can be reduced. As a result, a MEMS sensor with the first electrode and the second electrode with less variation in size can be manufactured. 
     Such a MEMS sensor includes, for example, similar to the MEMS sensor according to still another aspect of the present invention, a Si substrate having a surface layer portion on which a recess is formed, and comb-tooth-like first electrode and second electrode that are disposed directly above the recess of the Si substrate and have a lamination structure including a base film made of an insulating material and a polysilicon layer laminated in order from the side close to the recess, and engage with each other via an interval. 
     With the present arrangement, the variation in size of the comb-tooth-like first electrode and second electrode that engage with each other is small, so that the detection accuracy of the sensor can be improved. 
     The material that has etching selectivity to Si (in this paragraph, defined as material A) is, for example, a material satisfying a ratio (etching selectivity) of the etching rate of Si with a certain etching medium to the etching rate of the material A with this etching medium=(etching rate of material A/etching rate of Si)≠1. In particular, the material A is preferably a material that can make the etching selectivity closer to 0 (zero) (etching selectivity≈0), and specifically, the material A is preferably SiO 2 . 
     In the method for manufacturing a MEMS sensor according to still another aspect of the present invention, preferably, the step of forming the base film includes a step of processing the Si substrate into a plate-shaped base portion and columnar portions standing on the surface of the base portion by selectively etching the Si substrate, and a step of altering the surface of the base portion and the columnar portions into insulating films by thermally oxidizing the surface of the base portion and the columnar portions, and the step of selectively etching the polysilicon layer and the base film includes a step of etching to insulate the first electrode and/or the second electrode from other portions of the polysilicon layer by the columnar portions altered into the insulating films, respectively. 
     By this method, the MEMS sensor according to still another aspect of the present invention further including first insulating layers that are embedded in the first electrode so as to penetrate through the polysilicon layer and reach the base film and selectively insulate certain portions of the first electrode from other portions of the polysilicon layer, can be manufactured. Further, the MEMS sensor according to still another aspect of the present invention further including second insulating layers that are embedded in the second electrode so as to reach the base film by penetrating through the polysilicon layer and selectively insulate certain portions of the second electrode from other portions of the polysilicon layer, can be manufactured. 
     In the invention described in Patent Document 1 (U.S. Pat. No. 6,792,804), a plurality of portions that should be electrically insulated of the Si substrate are isolated by isolation joints (isolation joints 160, 360 . . . ). The isolation joints are formed by forming trenches in the Si substrate and thermally oxidizing the inner walls (side walls and bottom walls) of the trenches as shown in FIG. 6a of Patent Document 1. When the inner walls of the trenches are thermally oxidized, SiO 2  grows from the side walls and the bottom walls toward the insides of the trenches, and SiO 2  that grew from the walls are eventually integrated together. Due to this integration, the isolation joint (612 in FIG. 6a) embedded in the trenches is obtained. However, the isolation joint to be thus obtained is a film formed by integrating multiple SiO 2  growing inside the trenches that were originally void, so that the strength thereof is not so high, and formation takes time. 
     In the method for manufacturing a MEMS sensor according to still another aspect of the present invention, the shapes of the first insulating layers and the second insulating layers are formed as columnar portions by etching the Si substrate with a neat crystal structure. Next, the columnar portions are altered into insulating films by thermal oxidization. Next, around the insulating films, a polysilicon layer is formed and etched into the shapes of the first electrode and the second electrode. Specifically, in this manufacturing method, the shapes of the first insulating layers and the second insulating layers are formed by etching the Si, so that they can be formed as insulating layers having high strength in a short time as compared with the isolation joint forming method described in Patent Document 1. 
     In the method for manufacturing a MEMS sensor according to still another aspect of the present invention, the step of forming the polysilicon layer preferably includes a step of depositing a polysilicon material to a position higher than the top portions of the columnar portions on the base portion, and a step of grinding the polysilicon material until the surfaces of the deposited polysilicon material are lowered to the positions of the heights of the top portions of the columnar portions. 
     By this method, a polysilicon layer having thicknesses equal to the heights of the insulating films formed of the columnar portions can be formed. Therefore, certain portions of the first electrode and the second electrode can be reliably insulated from other portions of the polysilicon layer. 
     The method for manufacturing a MEMS sensor according to still another aspect of the present invention preferably further includes a step of forming a protective film having etching selectivity to polysilicon so as to cover the side walls of the first electrode and the second electrode. 
     According to this method, the side walls of the first electrode and the second electrode are covered by the protective film having etching selectivity to Si. Therefore, when a cavity is formed by isotropic etching of the Si substrate, even if an etching medium comes into contact with the side walls of the first electrode and the second electrode, erosion of the first electrode and the second electrode can be reduced. As a result, the variation in size of the first electrode and the second electrode can be further reduced. 
     The method for manufacturing a MEMS sensor according to still another aspect of the present invention preferably includes a step of selectively forming wirings on the polysilicon layer previous to formation of the trenches. 
     According to this method, wirings are formed on the polysilicon layer before the polysilicon layer is molded into complicated comb-tooth-like first electrode and second electrode, so that the wirings for contact with the first electrode and the second electrode can be easily formed. 
     In the MEMS sensor according to still another aspect of the present invention, the first electrode may be a movable electrode and the second electrode may be a fixed electrode. Alternatively, the first electrode may be a fixed electrode and the second electrode may be a movable electrode. 
     The MEMS sensor according to still another aspect of the present invention may include an acceleration sensor that detects acceleration applied to the MEMS sensor by detecting a change in capacitance between the first electrode and the second electrode. 
     With the present arrangement, acceleration can be detected by a capacitor consisting of the first electrode and the second electrode with less variation in size. Therefore, acceleration applied to the sensor can be accurately detected. 
     The MEMS sensor according to still another aspect of the present invention may include an angular velocity sensor that drives the first electrode in directions approaching and away from the recess and detects an angular velocity applied to the MEMS sensor at the time of this driving by detecting a change in capacitance between the first electrode and the second electrode. 
     With the present arrangement, the variation in size of the first electrode is small, so that the first electrode can be driven as designed. Therefore, an angular velocity applied to the sensor can be accurately detected. 
     In the MEMS sensor according to still another aspect of the present invention, the thickness of the base film may be 2 μm to 10 μm. The thickness of the polysilicon layer may be 5 μm to 20 μm. 
     A MEMS package according to still another aspect of the present invention includes the MEMS sensor according to still another aspect of the present invention and a resin package formed to cover the MEMS sensor. 
     With the present arrangement, the MEMS sensor according to still another aspect of the present invention is used. Therefore, in the MEMS sensor, the variation in size of the comb-tooth-like first electrode and second electrode that engage with each other can be reduced, so that the detection accuracy of the sensor can be improved. As a result, a MEMS package including a MEMS sensor with excellent detection accuracy can be provided. 
     The MEMS package according to still another aspect of the present invention may further include an integrated circuit electrically connected to the MEMS sensor and covered together with the MEMS sensor by the same resin package. When the MEMS package according to still another aspect of the present invention further includes a substrate that has a surface and a back surface and supports the MEMS sensor by the surface, the resin package may seal the MEMS sensor so as to cover the surface of the substrate and expose the back surface of the substrate. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     (1) First Preferred Embodiment 
     Entire Arrangement of Gyro Sensor 
       FIG. 1  is a schematic plan view of a gyro sensor according to a first preferred embodiment of the present invention. 
     The gyro sensor  1 A is a capacitance type angular velocity sensor that detects an angular velocity based on a change in capacitance of a capacitor, and is used for, for example, correcting shake of a video camera or a still camera, detecting a position of a car navigation system, and detecting motions of a robot and a gaming machine, etc. 
     The gyro sensor  1 A includes a semiconductor substrate  2 A quadrilateral in a plan view, a sensor portion  3 A disposed at the central portion of the semiconductor substrate  2 A, and electrode pads  4 A that are disposed on the lateral side of the sensor portion  3 A on the semiconductor substrate  2 A and for supplying voltages to the sensor portion  3 A. 
     The sensor portion  3 A includes an X-axis sensor  5 A, a Y-axis sensor  6 A, and Z-axis sensors  7 A as sensors that respectively detect angular velocities around the three axes orthogonal to each other in the three-dimensional space. These three sensors  5 A to  7 A are covered and sealed by a lid substrate  8 A by, for example, bonding the lid substrate  8 A formed of a silicon substrate to the surface of a semiconductor substrate  2 A. 
     The X-axis sensor  5 A generates a coriolis force Fz in the Z-axis direction by using oscillation Ux in the X-axis direction when the gyro sensor  1 A is tilted, and detects an angular velocity ωy applied around the Y axis by detecting a change in capacitance caused by the coriolis force. The Y-axis sensor  6 A generates a coriolis force Fx in the X-axis direction by using oscillation Uy in the Y-axis direction when the gyro sensor  1 A is tilted, and detects an angular velocity ωz applied around the Z axis by detecting a change in capacitance caused by the coriolis force. The Z-axis sensor  7 A generates a coriolis force Fy in the Y-axis direction by using oscillation Uz in the Z-axis direction when the gyro sensor  1 A is tilted, and detects an angular velocity ωx applied around the X-axis by detecting a change in capacitance caused by the coriolis force. 
     A plurality (five in  FIG. 1 ) of electrode pads  4 A are provided at even intervals. 
     &lt;Arrangement of X-Axis Sensor and Y-Axis Sensor&gt; 
     Next, the arrangement of the X-axis sensor and the Y-axis sensor will be described with reference to  FIG. 2  to  FIG. 4 . 
       FIG. 2  is a schematic plan view of a sensor portion shown in  FIG. 1 .  FIG. 3  is a plan view of a principal portion of the X-axis sensor shown in  FIG. 2 .  FIG. 4  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 2 , illustrating a section taken along the cutting plane A-A in  FIG. 3 . 
     The semiconductor substrate  2 A is formed of a conductive silicon substrate (low-resistance substrate with a resistivity of, for example, 5 Ω·m to 500 Ω·m). This semiconductor substrate  2 A has a cavity  10 A inside, and in the upper wall  11 A (surface portion) of the semiconductor substrate  2 A having a ceiling that partitions the cavity  10 A from the surface side, the X-axis sensor  5 A, the Y-axis sensor  6 A, and the Z-axis sensors  7 A are formed. Specifically, the X-axis sensor  5 A, the Y-axis sensor  6 A, and the Z-axis sensors  7 A are formed of portions of the semiconductor substrate  2 A, and are supported while in a floating state with respect to the bottom wall  12 A of the semiconductor substrate  2 A that has a bottom surface partitioning the cavity  10 A from the back surface side. 
     The X-axis sensor  5 A and the Y-axis sensor  6 A are disposed adjacent to each other at an interval, and the Z-axis sensors  7 A are disposed to surround the X-axis sensor  5 A and Y-axis sensor  6 A, respectively. In the present preferred embodiment, the Y-axis sensor  6 A has an arrangement that is substantially the same as an arrangement obtained by rotating 90 degrees the X-axis sensor  5 A in a plan view. Therefore, hereinafter, instead of a detailed description of the arrangement of the Y-axis sensor  6 A, in the description of the portions of the X-axis sensor  5 A, portions of the Y-axis sensor corresponding to the portions of the X-axis sensor are also described with parentheses. 
     Between the X-axis sensor  5 A and the Z-axis sensor  7 A and between the Y-axis sensor  6 A and the Z-axis sensor  7 A, support portions  14 A for supporting these in a floating state are formed. The support portions  14 A integrally include straight portions  16 A extending across the Z-axis sensors  7 A from one side walls  15 A having side surfaces that partition the cavity  10 A of the semiconductor substrate  2 A from the lateral sides toward the X-axis sensor  5 A and the Y-axis sensor  6 A, and annular portions  17 A surrounding the X-axis sensor  5 A and the Y-axis sensor  6 A. 
     The X-axis sensor  5 A and the Y-axis sensor  6 A are disposed inside the annular portions  17 A, and both ends of these sensors are supported at two points opposing each other on the inner walls of the annular portions  17 A. Both ends of the Z-axis sensors  7 A are supported on both side walls of the straight portions  16 A. 
     The X-axis sensor  5 A (Y-axis sensor  6 A) includes an X fixed electrode  21 A (Y fixed electrode  41 A) fixed to the support portion  14 A provided inside the cavity  10 A, and an X movable electrode  22 A (Y movable electrode  42 A) held to be capable of oscillating with respect to the X fixed electrode  21 A. The X fixed electrode  21 A and the X movable electrode  22 A are formed to have the same thickness. 
     The X fixed electrode  21 A (Y fixed electrode  41 A) includes a base portion  23 A (base portion  43 A of the Y fixed electrode  41 A) that is fixed to the support portion  14 A and has a quadrilateral annular shape in a plan view, and a plurality of pairs of comb tooth portions  24 A (comb tooth portions  44 A of the Y fixed electrode  41 A) aligned like comb teeth at even intervals along the inner wall of the base portion  23 A. 
     On the other hand, the X movable electrode  22 A (Y movable electrode  42 A) includes a base portion  26 A (base portion  46 A of the Y movable electrode  42 A) that extends in a direction across the comb tooth portions  24 A of the X fixed electrode  21 A and has both ends connected to the base portion  23 A of the X fixed electrode  21 A via expandable beam portions  25 A (beam portions  45 A of the Y-axis sensor  6 A) along the direction across the comb tooth portions  24 A, and comb tooth portions  27 A (comb tooth portions  47 A of the Y movable electrode  42 A) that extend from the base portion  26 A to both sides toward the portions between the comb tooth portions  24 A adjacent to each other of the X fixed electrode  21 A, and are aligned like comb teeth that engage with the comb tooth portions  24 A of the X fixed electrode  21 A without contact. 
     In the X-axis sensor  5 A, when the beam portions  25 A expand and contract and the base portion  26 A of the X movable electrode  22 A oscillates along the surface of the semiconductor substrate  2 A (oscillation Ux), the comb tooth portions  27 A of the X movable electrode  22 A that engage with the comb tooth portions  24 A like comb teeth of the X fixed electrode  21 A oscillate alternately in directions approaching and away from the comb tooth portions  24 A of the X fixed electrode  21 A. 
     The base portion  23 A of the X fixed electrode  21 A has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     As the comb tooth portions  24 A of the X fixed electrode  21 A, two electrode portions straight in a plan view that have base end portions connected to the base portion  23 A and tip end portions thereof opposed to each other are paired, and a plurality of the pairs are provided at even intervals. Each comb tooth portion  24 A has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other and a plurality of traverse frames laid across the main frames. 
     On the other hand, the base portion  26 A of the X movable electrode  22 A is formed of a plurality (six in the present preferred embodiment) of straight frames extending parallel to each other, and both ends thereof are connected to beam portions  25 A. Two beam portions  25 A are provided on each of both ends of the base portion  26 A of the X movable electrode  22 A. 
     Each comb tooth portion  27 A of the X movable electrode  22 A has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other across the frames of the base portion  26 A and a plurality of traverse frames laid across the main frames. 
     In the X movable electrode  22 A, on lines halving the comb tooth portions  27 A in a direction orthogonal to the oscillation direction Ux, insulating layers  28 A (silicon oxide in the present preferred embodiment) across the traverse frames are embedded from the surface to the cavity  10 A. By the insulating layer  28 A, each comb tooth portion  27 A is insulated and separated into two of one side and the other side along the oscillation direction Ux. Accordingly, the separated comb tooth portions  27 A of the X movable electrode  22 A function as independent electrodes respectively in the X movable electrode  22 A. 
     On the surface of the semiconductor substrate  2 A including the X fixed electrode  21 A and the X movable electrode  22 A, a first insulating film  33 A and a second insulating film  34 A made of silicon oxide (SiO 2 ) are laminated in order, and on this second insulating film  34 A, an X first drive/detection wiring  29 A (Y first drive/detection wiring  49 A) and an X second drive/detection wiring  30 A (Y second drive/detection wiring  50 A) are formed. 
     The X first drive/detection wiring  29 A supplies a drive voltage to one side (the left side on the paper surface shown in  FIG. 3  in the present preferred embodiment) of each comb tooth portion  27 A insulated and separated into two, and detects a change in voltage accompanying a change in capacitance from the comb tooth portion  27 A. On the other hand, the X second drive/detection wiring  30 A supplies a drive voltage to the other side (the right side on the paper surface shown in  FIG. 3  in the present preferred embodiment) of each comb tooth portion  27 A insulated and separated into two, and detects a change in voltage accompanying a change in capacitance from the comb tooth portion  27 A. 
     The X first and X second drive/detection wirings  29 A and  30 A are made of aluminum (Al) in the present preferred embodiment. The X first and X second drive/detection wirings  29 A and  30 A are electrically connected to the comb tooth portions  27 A by penetrating through the first and second insulating films  33 A and  34 A. 
     The X first and X second drive/detection wirings  29 A and  30 A are led onto the support portion  14 A via the beam portions  25 A of the X movable electrode  22 A and the base portion  23 A of the X fixed electrode  21 A, and are partially exposed as electrode pads  4 A. The X first and X second drive/detection wirings  29 A and  30 A use the beam portions  25 A themselves formed of portions of the conductive semiconductor substrate  2 A as current paths in sections passing through the beam portions  25 A of the X movable electrode  22 A, respectively. No aluminum wiring is provided on the beam portions  25 A, so that the expandability of the beam portions  25 A can be maintained. 
     To the support portion  14 A, an X third drive/detection wiring  32 A that detects a change in voltage caused by a change in capacitance from the comb tooth portions  24 A of the X fixed electrode  21 A is led, and this X third drive/detection wiring  32 A is also partially exposed as an electrode pad  4 A (not shown) in the same manner as other wirings  29 A and  30 A. 
     On the semiconductor substrate  2 A, the upper surfaces and the side surfaces of the X fixed electrode  21 A and the X movable electrode  22 A are coated together with the first insulating film  33 A and the second insulating film  34 A by a protective thin film  35 A made of silicon oxide (SiO 2 ). 
     On portions except for the cavity  10 A of the surface of the semiconductor substrate  2 A, a third insulating film  36 A, a fourth insulating film  37 A, a fifth insulating film  38 A, and a surface protective film  39 A are laminated in order on the second insulating film  34 A. 
     In the X-axis sensor  5 A structured as described above, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the X fixed electrode  21 A and the X movable electrode  22 A via the X first to X third drive/detection wirings  29 A,  30 A, and  32 A. Accordingly, between the comb tooth portions  24 A of the X fixed electrode  21 A and the comb tooth portions  27 A of the X movable electrode  22 A, coulomb repulsive and attractive forces are alternately generated. As a result, the comb-tooth-like X movable electrode  22 A oscillates similarly to the left and right along the X-axis direction with respect to the comb-tooth-like X fixed electrode  21 A (oscillation Ux). In this state, when the X movable electrode  22 A rotates around the Y axis as a central axis, a coriolis force Fz is generated in the Z-axis direction. This coriolis force Fz changes the opposing area and/or distance between the comb tooth portions  24 A of the X fixed electrode  21 A and the comb tooth portions  27 A of the X movable electrode  22 A adjacent to each other. Then, by detecting a change in capacitance between the X movable electrode  22 A and the X fixed electrode  21 A caused by the change in opposing area and/or distance, the angular velocity ωy around the Y axis is detected. 
     In the present preferred embodiment, the angular velocity ωy around the Y axis is obtained by calculating a difference between detection values of one-side and the other-side electrode portions insulated and separated from each other of the X movable electrode  22 A. 
     In the Y-axis sensor  6 A, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the Y fixed electrode  41 A and the Y movable electrode  42 A via the Y first to Y third drive/detection wirings  49 A,  50 A, and  52 A. Accordingly, coulomb repulsive and attractive forces are alternately generated between the comb tooth portions  44 A of the Y fixed electrode  41 A and the comb tooth portions  47 A of the Y movable electrode  42 A. As a result, the comb-tooth-like Y movable electrode  42 A oscillates similarly to the left and right along the Y-axis direction with respect to the comb-tooth-like Y fixed electrode  41 A (oscillation Uy). In this state, when the Y movable electrode  42 A rotates around the Y axis as a central axis, a coriolis force Fx is generated in the X-axis direction. This coriolis force Fx changes the opposing area and/or distance between the comb tooth portions  44 A of the Y fixed electrode  41 A and the comb tooth portions  47 A of the Y movable electrode  42 A adjacent to each other. Then, by detecting a change in capacitance between the Y movable electrode  42 A and the Y fixed electrode  41 A caused by the change in opposing area and/or distance, the angular velocity ωz around the Z axis is detected. 
     &lt;Arrangement of Z-Axis Sensors&gt; 
     Next, an arrangement of the Z-axis sensors will be described with reference to  FIG. 2 ,  FIG. 5 , and  FIG. 6 . 
       FIG. 5  is a plan view of a principal portion of the Z-axis sensor shown in  FIG. 2 .  FIG. 6  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 2 , illustrating a section taken along the cutting plane B-B in  FIG. 5 . 
     Referring to  FIG. 2 , the semiconductor substrate  2 A made of conductive silicon has a cavity  10 A inside as described above. In the upper wall  11 A (surface portion) of the semiconductor substrate  2 A, the Z-axis sensors  7 A supported by the support portions  14 A while in a floating state with respect to the bottom wall  12 A of the semiconductor substrate  2 A are disposed to surround the X-axis sensor  5 A and the Y-axis sensor  6 A, respectively. 
     Each Z-axis sensor  7 A includes a Z fixed electrode  61 A as a first electrode fixed to the support portion  14 A (straight portion  16 A) provided inside the cavity  10 A, and a Z movable electrode  62 A as a second electrode held to be capable of oscillating with respect to the Z fixed electrode  61 A. The Z fixed electrode  61 A and the Z movable electrode  62 A are formed to have the same thickness. 
     In one Z-axis sensor  7 A of these two Z-axis sensors  7 A, the Z movable electrode  62 A is disposed to surround the annular portion  17 A of the support portion  14 A, and the Z fixed electrode  61 A is disposed to further surround the Z movable electrode  62 A. In the other Z-axis sensor  7 A, the Z fixed electrode  61 A is disposed to surround the annular portion  17 A of the support portion  14 A, and the Z movable electrode  62 A is disposed to further surround the Z fixed electrode  61 A. The Z fixed electrode  61 A and the Z movable electrode  62 A are connected integrally to both side walls of the straight portion  16 A of the support portion  14 A. 
     The Z fixed electrode  61 A includes a first base portion  63 A having a quadrilateral annular shape in a plan view fixed to the support portion  14 A, and a plurality of comb-tooth-like first comb tooth portions  64 A provided on the portion opposite to the straight portion  16 A with respect to the X-axis sensor  5 A (Y-axis sensor  6 A) of the first base portion  63 A. 
     On the other hand, the Z movable electrode  62 A includes a second base portion  65 A having a quadrilateral annular shape in a plan view, and comb-tooth-like second comb tooth portions  66 A extending from the second base portion  65 A toward the portions between the comb-tooth-like first comb tooth portions  64 A of the Z fixed electrode  61 A adjacent to each other that engage with the first comb tooth portions  64 A of the Z fixed electrode  61 A without contact. The second base portion  65 A of the Z movable electrode  62 A has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. The second base portion  65 A of the Z movable electrode  62 A thus structured has sections in which the reinforcing frames are omitted at portions on the side opposite to the side of disposition of the second comb tooth portions  66 A, and the main frames in the sections function as beam portions  67 A for enabling the Z movable electrode  62 A to move up and down. 
     Specifically, in this Z-axis sensor  7 A, the beam portions  67 A elastically warp, and the second base portion  65 A of the Z movable electrode  62 A turns like a pendulum in directions approaching and away from the cavity  10 A around the beam portions  67 A as pivot points (oscillation Uz), and accordingly, the second comb tooth portions  66 A of the Z movable electrode  62 A engaging with the first comb tooth portions  64 A of the Z fixed electrode  61 A like comb teeth oscillate up and down. 
     The first base portion  63 A of the Z fixed electrode  61 A has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     The first comb tooth portions  64 A of the Z fixed electrode  61 A have base end portions connected to the first base portion  63 A of the Z fixed electrode  61 A and tip end portions extending toward the Z movable electrode  62 A, and are aligned like comb teeth at even intervals along the inner wall of the first base portion  63 A. In portions close to the base end portions of the first comb tooth portions  64 A, insulating layers  68 A (silicon oxide in the present preferred embodiment) are embedded across the first comb tooth portions  64 A in the width direction from the surface to the cavity  10 A. By the insulating layers  68 A, the first comb tooth portions  64 A of the Z fixed electrode  61 A are insulated from other portions of the Z fixed electrode  61 A. 
     In the first base portion  63 A of the Z fixed electrode  61 A, on both sides of a portion (opposed portion  84 A) opposed to the tip end portion  70 A (described later) of each second comb tooth portion  66 A of the Z movable electrode  62 A, insulating layers  69 A as first separating and insulating layers are embedded across the main frame of the truss structure in the width direction from the surface to the cavity  10 A of the semiconductor substrate  2 A. Accordingly, the opposed portion  84 A surrounded by the insulating layers  69 A and the triangular space of the truss structure is insulated from other portions of the first base portion  63 A of the Z fixed electrode  61 A. 
     To the opposed portions  84 A, the first drive portions  18 A extending toward the tip end portions  70 A (described later) of the second comb tooth portions  66 A disposed in front of the opposed portions are connected integrally. Specifically, the first drive portions  18 A are provided between the first comb tooth portions  64 A aligned like comb teeth on the first base portion  63 A of the Z fixed electrode  61 A. Therefore, on the entire first base portion  63 A of the Z fixed electrode  61 A, the first comb tooth portions  64 A and the first drive portions  18 A shorter than the first comb tooth portions  64 A are aligned like comb teeth at even intervals. 
     On the other hand, the second comb tooth portions  66 A of the Z movable electrode  62 A have base end portions  71 A connected to the second base portion  65 A of the Z movable electrode  62 A and tip end portions  70 A extending toward the portions between the first comb tooth portions  64 A of the Z fixed electrode  61 A, and are aligned like comb teeth that engage with the first comb tooth portions  64 A of the Z fixed electrode  61 A without contact therebetween. In portions close to the tip end portions  70 A of the second comb tooth portions  66 A of the Z movable electrode  62 A, insulating layers  73 A (silicon oxide in the present preferred embodiment) as second separating and insulating layers are embedded across the second comb tooth portions  66 A in the width direction from the surface to the cavity  10 A of the semiconductor substrate  2 A. In portions close to the base end portions  71 A of the second comb tooth portions  66 A of the Z movable electrode  62 A, insulating layers  74 A (silicon oxide in the present preferred embodiment) are embedded across the second comb tooth portions  66 A in the width direction from the surface to the cavity  10 A of the semiconductor substrate  2 A. Each second comb tooth portion  66 A has three portions (the tip end portion  70 A, the base end portion  71 A, and the intermediate portion  72 A between the tip end portion  70 A and the base end portion  71 A) insulated from other portions by these insulating layers  73 A and  74 A. 
     The tip end portions  70 A of the second comb tooth portions  66 A integrally include second drive portions  19 A formed like comb teeth. Specifically, the Z movable electrode  62 A includes a plurality of second comb tooth portions  66 A aligned like comb teeth, and on the tip end portion  70 A of each second comb tooth portion  66 A, a second drive portion  19 A having a comb-tooth-like shape smaller than the second comb tooth portion  66 A is formed. The second drive portions  19 A engage with the first drive portions  18 A of the Z fixed electrode  61 A while being spaced from each other so as not to come into contact with each other. 
     On the surface of the semiconductor substrate  2 A including the Z fixed electrode  61 A and the Z movable electrode  62 A, a first insulating film  33 A and a second insulating film  34 A made of silicon oxide (SiO 2 ) are laminated in order as described above. On the second insulating layer  34 A, a Z first detection wiring  75 A, Z first drive wiring  76 A as a first detection wiring, a Z second detection wiring  77 A, Z second drive wiring  78 A as a second detection wiring are formed. In the present preferred embodiment, the Z first detection wiring  75 A and the Z first drive wiring  76 A constitute a first contact wiring that comes into direct contact with the Z fixed electrode  61 A from the surface side of the semiconductor substrate  2 A. Also, the Z second detection wiring  77 A and the Z second drive wiring  78 A constitute a second contact wiring that comes into direct contact with the Z movable electrode  62 A from the surface side of the semiconductor substrate  2 A. 
     The Z first detection wiring  75 A and the Z second detection wiring  77 A are connected to the first comb tooth portions  64 A of the Z fixed electrode  61 A and the intermediate portions  72 A of the Z movable electrode  62 A adjacent to each other, respectively. Specifically, in this Z-axis sensor  7 A, the first comb tooth portions  64 A of the Z fixed electrode  61 A and the intermediate portions  72 A of the Z movable electrode  62 A to which the Z first detection wiring  75 A and the Z second detection wiring  77 A are connected are opposed to each other at an electrode-to-electrode distance d, and constitutes electrodes of a capacitor (detector) when a fixed voltage is applied between the electrodes and the capacitance of the capacitor changes according to a change in electrode-to-electrode distance d and/or opposing area. 
     In detail, the Z first detection wiring  75 A is formed along the first base portion  63 A of the Z fixed electrode  61 A and includes aluminum wirings branched toward the tip end portions of the first comb tooth portions  64 A across the insulating layers  68 A of the first comb tooth portions  64 A of the Z fixed electrode  61 A. The branched aluminum wirings are electrically connected to the tip end sides relative to the insulating layers  68 A of the first comb tooth portions  64 A by penetrating through the first insulating film  33 A and the second insulating film  34 A. As shown in  FIG. 2 , the Z first detection wiring  75 A is led onto the support portion  14 A via the first base portion  63 A of the Z fixed electrode  61 A, and is partially exposed as an electrode pad  4 A. 
     On the other hand, the Z second detection wiring  77 A detects a change in voltage accompanying a change in capacitance from the second comb tooth portions  66 A of the Z movable electrode  62 A. This Z second detection wiring  77 A is formed along the second base portion  65 A of the Z movable electrode  62 A, and includes aluminum wirings branched toward the intermediate portions  72 A across the insulating layers  74 A close to the base end portions  71 A of the second comb tooth portions  66 A of the Z movable electrode  62 A. The branched aluminum wirings are electrically connected to the intermediate portions  72 A of the second comb tooth portions  66 A by penetrating through the first insulating film  33 A and the second insulating film  34 A. As shown in  FIG. 2 , the Z second detection wiring  77 A is led onto the support portion  14 A via the second base portion  65 A of the Z movable electrode  62 A, and partially exposed as an electrode pad  4 A. 
     The Z first drive wiring  76 A and the Z second drive wiring  78 A are respectively connected to the opposed portions  84 A (first drive portions  18 A) of the Z fixed electrode  61 A and the tip end portions  70 A (second drive portions  19 A) of the Z movable electrode  62 A that face each other in a direction orthogonal to the opposing direction of electrodes constituting a capacitor. Specifically, in this Z-axis sensor  7 A, the first drive portions  18 A of the Z fixed electrode  61 A and the second drive portions  19 A of the Z movable electrode  62 A that engage with each other like comb teeth at an interval constitute drive portions between which drive voltages are applied to oscillate the Z movable electrode  62 A by coulomb forces generated by changes in the drive voltages. 
     In detail, the Z first drive wiring  76 A supplies a drive voltage to the opposed portions  84 A (first drive portions  18 A) of the Z fixed electrode  61 A. The Z first drive wiring  76 A includes aluminum wirings that are laid across both sides of the insulating layers  69 A by using the surface of the second insulating film  34 A and electrically connected to the opposed portions  84 A and portions except for the opposed portions  84 A of the first base portion  63 A by penetrating through the first insulating film  33 A and the second insulating film  34 A, and a remaining portion of the Z first drive wiring is formed by using the first base portion  63 A of the Z fixed electrode  61 A made of conductive silicon. As shown in  FIG. 2 , the Z first drive wiring  76 A is led onto the support portion  14 A, and partially exposed as an electrode pad  4 A. 
     On the other hand, the Z second drive wiring  78 A supplies a drive voltage to the tip end portions  70 A (second drive portions  19 A) of the Z movable electrode  62 A. The Z second drive wiring  78 A includes aluminum wirings that are laid across the tip end portions  70 A and the base end portions  71 A of the second comb tooth portions  66 A by using the surface of the second insulating film.  34 A, and electrically connected to the tip end portions  70 A and the base end portions  71 A by penetrating through the first insulating film  33 A and the second insulating film  34 A, and a remaining portion of the Z second drive wiring is formed by using the second base portion  65 A of the Z movable electrode  62 A made of conductive silicon. As shown in  FIG. 2 , the Z second drive wiring  78 A is led onto the support portion  14 A and partially exposed as an electrode pad  4 A. 
     On the semiconductor substrate  2 A, the upper surfaces and the side surface of the Z fixed electrode  61 A and the Z movable electrode  62 A are coated together with the first insulating film  33 A and the second insulating film  34 A by the protective thin film  35 A made of silicon oxide (SiO 2 ). 
     On portions except for the cavity  10 A of the surface of the semiconductor substrate  2 A, the third insulating film  36 A, the fourth insulating film  37 A, the fifth insulating film  38 A, and the surface protective film  39 A are laminated in order on the second insulating film  34 A. 
     In this Z-axis sensor  7 A, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the opposed portions  84 A (first drive portions  18 A) of the Z fixed electrode  61 A and the tip end portions  70 A (second drive portions  19 A) of the Z movable electrode  62 A via the Z first drive wiring  76 A and the Z second drive wiring  78 A. Accordingly, coulomb repulsive and attractive forces are alternately generated between the first drive portions  18 A of the Z fixed electrode  61 A and the second drive portions  19 A of the Z movable electrode  62 A. As a result, the comb-tooth-like Z movable electrode  62 A oscillates up and down like a pendulum similarly around the comb-tooth-like Z fixed electrode  61 A as a center of oscillation along the Z-axis direction with respect to the Z fixed electrode  61 A (oscillation Uz). In this state, when the Z movable electrode  62 A rotates around the X axis as a central axis, a coriolis force Fy is generated in the Y-axis direction. This coriolis force Fy changes the opposing area S and/or electrode-to-electrode distance d between the first comb tooth portions  64 A of the Z fixed electrode  61 A and the intermediate portions  72 A of the second comb tooth portions  66 A of the Z movable electrode  62 A adjacent to each other. Then, by detecting a change in capacitance C between the Z movable electrode  62 A and the Z fixed electrode  61 A caused by the change in opposing area S and/or electrode-to-electrode distance d via the Z first detection wiring  75 A and the Z second detection wiring  77 A, the angular velocity ωx around the X axis is detected. In the present preferred embodiment, the angular velocity ωx around the X axis is obtained by calculating a difference between a detection value of the Z-axis sensor  7 A surrounding the X-axis sensor  5 A and a detection value of the Z-axis sensor  7 A surrounding the Y-axis sensor  6 A. The difference can be provided, for example, as shown in  FIG. 2 , by making the position relationship of the fixed electrode and the movable electrode of the Z-axis sensor  7 A surrounding the X-axis sensor  5 A opposite to the position relationship of the fixed electrode and the movable electrode of the Z-axis sensor  7 A surrounding the Y-axis sensor  6 A. Accordingly, the manner of oscillation of the Z movable electrode  62 A differs between the pair of Z-axis sensors  7 A, so that a difference occurs. 
     In this gyro sensor  1 A, the first drive portions  18 A and the second drive portions  19 A for driving (oscillating) the Z movable electrode  62 A are disposed to engage with each other like comb teeth. Therefore, for example, as compared with cases such as where the side walls of the opposed portions  84 A of the Z fixed electrode  61 A and the side walls of the Z movable electrode  62 A are both flat and just opposed to each other, the opposing area between the drive electrodes (in the present preferred embodiment, the opposing area between the side surface of the drive portion  18 A and the side surface of the second drive portion  19 A) can be made larger. Therefore, the Z movable electrode  62 A can be oscillated with a large amplitude, so that the detection sensitivity can be improved. 
     In the gyro sensor  1 A, the Z fixed electrode  61 A and the Z movable electrode  62 A are formed by using the upper wall  11 A of the semiconductor substrate  2 A having the cavity  10 A in the surface portion of the semiconductor substrate  2 A. Therefore, the thickness of the entire sensor is substantially the thickness of the semiconductor substrate  2 A, so that the sensor can be downsized. 
     The insulating layers  68 A,  69 A,  73 A and  74 A for insulating and separating the opposed portions  84 A of the Z fixed electrode  61 A and the base end portions  71 A, the intermediate portions  72 A, and the tip end portions  70 A of the Z movable electrode  62 A are embedded in the semiconductor substrate  2 A, so that the surface of the semiconductor substrate  2 A can be efficiently used as a space for leading the aluminum wirings of the X first drive/detection wiring  29 A and the Z first detection wiring  75 A, etc. 
     Further, the semiconductor substrate  2 A is a conductive silicon substrate, so that even without applying a special treatment for giving conductivity to the X fixed electrode  21 A, the Y fixed electrode  41 A, and the Z fixed electrode  61 A, and the X movable electrode  22 A, the Y movable electrode  42 A, and the Z movable electrode  62 A molded into predetermined shapes, the molded structures can be used as they are as electrodes. The portions except for the portions to be used as electrodes can be used as wirings (the X first drive/detection wiring  29 A and the Z first detection wiring  75 A, etc.). 
     &lt;Method for Manufacturing Gyro Sensor  1 A&gt; 
     Next, a manufacturing process of the above-described gyro sensor will be described in order of steps with reference to  FIG. 7A  to  FIG. 7G . In this paragraph, only the manufacturing process of the Z-axis sensors is shown in the drawings, and the manufacturing processes of the X-axis sensor and the Y-axis sensor are omitted, however, the manufacturing processes of the X-axis sensor and the Y-axis sensor are performed in parallel to the manufacturing process of the Z-axis sensors in the same manner as the manufacturing process of the Z-axis sensors. 
       FIG. 7A  to  FIG. 7G  are schematic sectional views showing parts of the manufacturing process of the gyro sensor according to the first preferred embodiment of the present invention in order of steps, illustrating a section taken along the cutting plane at the same position as in  FIG. 6 . 
     To manufacture this gyro sensor  1 A, first, as shown in  FIG. 7A , the surface of the semiconductor substrate  2 A made of conductive silicon is thermally oxidized (for example, temperature: 1100 to 1200° C., film thickness: 5000 Å). Accordingly, the first insulating film  33 A is formed on the surface of the semiconductor substrate  2 A. Next, by a known patterning technique, the first insulating film  33 A is patterned, and openings are formed in regions in which the insulating layers  68 A,  69 A,  73 A, and  74 A should be embedded. Next, by anisotropic deep RIE (Reactive Ion Etching) using the first insulating film  33 A as a hard mask, specifically, by a Bosch process, the semiconductor substrate  2 A is dug. Accordingly, trenches are formed in the semiconductor substrate  2 A. In the Bosch process, a step of etching the semiconductor substrate  2 A by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. Accordingly, the semiconductor substrate  2 A can be etched at a high aspect ratio, however, a wavy irregularity called scallop is formed on the etched surfaces (inner peripheral surfaces of the trenches). Subsequently, the insides of the trenches formed in the semiconductor substrate  2 A and the surface of the semiconductor substrate  2 A are thermally oxidized (for example, temperature: 1100 to 1200° C.), and then, the surface of the oxide film is etched back (for example, the film thickness after etching back is 21800 Å). Accordingly, the insulating layers  68 A,  69 A,  73 A, and  74 A filling the trenches are formed (only the insulating layer  74 A is shown). 
     Next, as shown in  FIG. 7B , by a CVD method, the second insulating film  34 A made of silicon oxide is laminated on the semiconductor substrate  2 A. Next, the second insulating film  34 A and the first insulating film  33 A are successively etched. Accordingly, contact holes are formed in the second insulating film  34 A and the first insulating film  33 A. Next, contact plugs filling the contact holes are formed, and by sputtering, aluminum is deposited (for example, 7000 Å) on the second insulating film  34 A, and the aluminum deposit layer is patterned. Accordingly, the wirings  75 A to  78 A are formed on the second insulating film  34 A. 
     Next, as shown in  FIG. 7C , by a CVD method, the third insulating film  36 A, the fourth insulating film  37 A, the fifth insulating film  38 A, and the surface protective film  39 A are laminated in order on the second insulating film  34 A. Next, the third to fifth insulating films  36 A to  38 A and the surface protective film  39 A on the region in which the cavity  10 A of the semiconductor substrate  2 A should be formed are removed by etching. 
     Next, as shown in  FIG. 7D , a resist having openings in regions other than the regions in which the Z fixed electrode  61 A and the Z movable electrode  62 A should be formed is formed on the second insulating film  34 A. Subsequently, by anisotropic deep RIE using this resist as a mask, specifically, by a Bosch process, the semiconductor substrate  2 A is dug. Accordingly, the surface portion of the semiconductor substrate  2 A is molded into the shapes of the Z fixed electrode  61 A and the Z movable electrode  62 A, and between these, trenches  60 A are formed. In the Bosch process, a step of etching the semiconductor substrate  2 A by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. After the deep RIE, the resist is stripped. 
     Next, as shown in  FIG. 7E , by thermal oxidization or by a PECVD method, on the entire surfaces of the Z fixed electrode  61 A and the Z movable electrode  62 A and the entire inner surfaces of the trenches  60 A (that is, the side surfaces and the bottom surfaces that define the trenches  60 A), the protective thin film  35 A made of silicon oxide (SiO 2 ) is formed. 
     Next, as shown in  FIG. 7F , by etching back, the portions on the bottom surfaces of the trenches  60 A of the protective thin film  35 A are removed. Accordingly, the bottom surfaces of the trenches  60 A are exposed. 
     Next, as shown in  FIG. 7G , by anisotropic deep RIE using the surface protective film  39 A as a mask, the bottom surfaces of the trenches  60 A are further dug. Accordingly, at the bottom portions of the trenches  60 A, exposure spaces  83 A from which the crystal face of the semiconductor substrate  2 A is exposed are formed. Subsequent to this anisotropic deep RIE, by isotropic RIE, reactive ions and etching gas are supplied into the exposure spaces  83 A of the trenches  60 A. Then, by action of the reactive ions, etc., the semiconductor substrate  2 A is etched in a direction parallel to the surface of the semiconductor substrate  2 A while being etched in the thickness direction of the semiconductor substrate  2 A from the exposure spaces  83 A. Accordingly, all exposure spaces  83 A adjacent to each other are integrated together to form the cavity  10 A inside the semiconductor substrate  2 A, and in the cavity  10 A, the Z fixed electrode  61 A and the Z movable electrode  62 A float. 
     Through these steps, the gyro sensor  1 A (Z-axis sensor  7 A) shown in  FIG. 1  is obtained. 
     The first preferred embodiment of the present invention is described above, however the present invention can also be carried out in other embodiments. 
     For example, as long as the first drive portions  18 A and the second drive portions  19 A engage with each other at an interval, as shown in  FIG. 8 , they may be arranged so that the first drive portions  18 A are aligned like comb teeth and the second drive portions  19 A are disposed between the comb teeth, or both the first drive portions  18 A and the second drive portions  19 A are aligned like comb teeth. 
     (2) Second Preferred Embodiment 
     Entire Arrangement of Acceleration Sensor 
       FIG. 9  is a schematic plan view of an acceleration sensor according to a second preferred embodiment of the present invention. 
     The acceleration sensor  1 B includes the semiconductor substrate  2 B having a quadrilateral shape in a plan view, a sensor portion  3 B disposed at the central portion of the semiconductor substrate  2 B, and electrode pads  4 B that are disposed on the lateral side of the sensor portion  3 B of the semiconductor substrate  2 B and for supplying electric power to the sensor portion  3 B. 
     The sensor portion  3 B includes an X-axis sensor  5 B, a Y-axis sensor  6 B, and Z-axis sensors  7 B as sensors that detect accelerations applied in directions along three axes orthogonal to each other in a three-dimensional space. In the present preferred embodiment, the two directions orthogonal to each other along the surface of the semiconductor substrate  2 B are defined as the X-axis direction and the Y-axis direction, and a direction along the thickness direction of the semiconductor substrate  2 B orthogonal to these X-axis and Y-axis directions is defined as the Z-axis direction. 
     These three sensors  5 B to  7 B are covered and sealed by a lid substrate  8 B by bonding the lid substrate  8 B formed of, for example, a silicon substrate to the surface of the semiconductor substrate  2 B. 
     A plurality (five in  FIG. 9 ) of the electrode pads  4 B are provided at even intervals. 
     &lt;Arrangement of X-Axis Sensor and Y-Axis Sensor&gt; 
     Next, an arrangement of the X-axis sensor and the Y-axis sensor will be described with reference to  FIG. 10  to  FIG. 12 . 
       FIG. 10  is a schematic plan view of the sensor portion shown in  FIG. 9 .  FIG. 11  is a plan view of a principal portion of the X-axis sensor shown in  FIG. 10 .  FIG. 12  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 10 , illustrating a section taken along the cutting plane C-C in  FIG. 11 . 
     The semiconductor substrate  2 B is formed of a conductive silicon substrate (for example, a low-resistance substrate with resistivity of 5 Ω·m to 500 Ω·m). This semiconductor substrate  2 B has a cavity  10 B inside, and in the upper wall  11 B (surface portion) of the semiconductor substrate  2 B having a ceiling that partitions the cavity  10 B from the surface side, the X-axis sensor  5 B, the Y-axis sensor  6 B, and the Z-axis sensors  7 B are formed. Specifically, the X-axis sensor  5 B, the Y-axis sensor  6 B, and the Z-axis sensors  7 B are formed of portions of the semiconductor substrate  2 B, and are supported while in a floating state with respect to the bottom wall  12 B (back surface portion) of the semiconductor substrate  2 B having a bottom surface that partitions the cavity  10 B from the back surface side. 
     The X-axis sensor  5 B and the Y-axis sensor  6 B are disposed adjacent to each other at an interval, and the Z-axis sensors  7 B are disposed to surround the X-axis sensor  5 B and the Y-axis sensor  6 B, respectively. In the present preferred embodiment, the Y-axis sensor  6 B has an arrangement that is substantially the same as an arrangement obtained by rotating 90 degrees the X-axis sensor  5 B in a plan view. Therefore, hereinafter, instead of a detailed description of the arrangement of the Y-axis sensor  6 B, in the description of the portions of the X-axis sensor  5 B, portions of the Y-axis sensor corresponding to the portions of the X-axis sensor are also described with parentheses. 
     Between the X-axis sensor  5 B and the Z-axis sensor  7 B and between the Y-axis sensor  6 B and the Z-axis sensor  7 B, support portions  14 B for supporting these in a floating state are formed. The support portions  14 B integrally include straight portions  16 B extending across the Z-axis sensors  7 B from one side walls  15 B having side surfaces that partition the cavity  10 B of the semiconductor substrate  2 B from the lateral sides toward the X-axis sensor  5 B and the Y-axis sensor  6 B, and annular portions  17 B surrounding the X-axis sensor  5 B and the Y-axis sensor  6 B. 
     The X-axis sensor  5 B and the Y-axis sensor  6 B are disposed inside the annular portions  17 B, and both ends of these sensors are supported at two points opposing each other on the inner walls of the annular portions  17 B. Both ends of the Z-axis sensors  7 B are supported on both side walls of the straight portions  16 B. 
     The X-axis sensor  5 B (Y-axis sensor  6 B) includes an X fixed electrode  21 B (Y fixed electrode  41 B) fixed to the support portion  14 B provided inside the cavity  10 B, and an X movable electrode  22 B (Y movable electrode  42 B) held to be capable of oscillating with respect to the X fixed electrode  21 B. The X fixed electrode  21 B and the X movable electrode  22 B are formed to have the same thickness. 
     The X fixed electrode  21 B (Y fixed electrode  41 B) includes a base portion  23 B (base portion  43 B of the Y fixed electrode  41 B) that is fixed to the support portion  14 B and has a quadrilateral annular shape in a plan view, and a plurality of pairs of electrode portions  24 B (electrode portions  44 B of the Y fixed electrode  41 B) aligned like comb teeth at even intervals along the inner wall of the base portion  23 B. 
     The X movable electrode  22 B (Y movable electrode  42 B) includes a base portion  26 B (base portion  46 B of the Y movable electrode  42 B) that extends in a direction across the electrode portions  24 B of the X fixed electrode  21 B and has both ends connected to the base portion  23 B of the X fixed electrode  21 B via expandable beam portions  25 B (beam portions  45 B of the Y-axis sensor  6 B) along the direction across the electrode portions  24 B, and electrode portions  27 B (electrode portions  47 B of the Y movable electrode  42 B) that extend from the base portion  26 B to both sides toward the portions between the electrode portions  24 B adjacent to each other of the X fixed electrode  21 B, and are aligned like comb teeth that engage with the electrode portions  24 B of the X fixed electrode  21 B without contact. 
     In the X-axis sensor  5 B, when the beam portions  25 B expand and contract and the base portion  26 B of the X movable electrode  22 B oscillates along the surface of the semiconductor substrate  2 B (oscillation Ux), and accordingly, the electrode portions  27 B of the X movable electrode  22 B that engage with the electrode portions  24 B of the X fixed electrode  21 B like comb teeth oscillate alternately in directions approaching and away from the electrode portions  24 B of the X fixed electrode  21 B. 
     The base portion  23 B of the X fixed electrode  21 B has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     As the electrode portions  24 B of the X fixed electrode  21 B, two electrode portions straight in a plan view that have base end portions connected to the base portion  23 B and tip end portions thereof opposed to each other are paired, and a plurality of the pairs are provided at even intervals. Each electrode portion  24 B has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other and a plurality of traverse frames laid across the main frames. 
     The base portion  26 B of the X movable electrode  22 B is formed by a plurality (six in the present preferred embodiment) of straight frames extending parallel to each other, and both ends of the base portion are connected to the beam portions  25 B. Two beam portions  25 B are provided on each of the ends of the base portion  26 B of the X movable electrode  22 B. 
     Each electrode portion  27 B of the X movable electrode  22 B has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other across the frames of the base portion  26 B and a plurality of traverse frames laid across the main frames. 
     In the X movable electrode  22 B, on lines halving the electrode portions  27 B in a direction orthogonal to the oscillation direction Ux, insulating layers  28 B (silicon oxide in the present preferred embodiment) across the traverse frames are embedded from the surface to the cavity  10 B. By the insulating layer  28 B, each electrode portion  27 B is insulated and separated into two of one side and the other side along the oscillation direction Ux. Accordingly, the separated electrode portions  27 B of the X movable electrode  22 B function as independent electrodes in the X movable electrode  22 B. 
     On the surface of the semiconductor substrate  2 B including the X fixed electrode  21 B and the X movable electrode  22 B, a first insulating film  33 B and a second insulating film  34 B made of silicon oxide (SiO 2 ) are laminated in order. 
     On this second insulating film  34 B, an X first sensor wiring  29 B (Y first sensor wiring  49 B) and an X second sensor wiring  30 B (Y second sensor wiring  50 B) are formed. 
     The X first sensor wiring  29 B supplies a drive voltage to one side (in the present preferred embodiment, the left side on the paper surface shown in  FIG. 11 ) of each electrode portion  27 B insulated and separated into two, and detects a change in voltage accompanying a change in capacitance from the electrode portion  27 B. On the other hand, the X second sensor wiring  30 B supplies a drive voltage to the other side (in the present preferred embodiment, the right side on the paper surface shown in  FIG. 11 ) of each electrode portion  27 B insulated and separated into two, and detects a change in voltage accompanying a change in capacitance from the electrode portion  27 B. 
     The X first and X second sensor wirings  29 B and  30 B are made of aluminum (Al) in the present preferred embodiment. The X first and X second sensor wirings  29 B and  30 B are electrically connected to the electrode portions  27 B by penetrating through the first and second insulating films  33 B and  34 B. 
     The X first and X second sensor wirings  29 B and  30 B are led onto the support portion  14 B via the beam portions  25 B of the X movable electrode  22 B and the base portion  23 B of the X fixed electrode  21 B, and are partially exposed as electrode pads  4 B. The X first and X second sensor wirings  29 B and  30 B use the beam portions  25 B themselves formed of portions of the conductive semiconductor substrate  2 B as current paths in sections passing through the beam portions  25 B of the X movable electrode  22 B. No aluminum wiring is provided on the beam portions  25 B, so that the expandability of the beam portions  25 B can be maintained. 
     To the support portion  14 B, an X third sensor wiring  32 B that detects a change in voltage caused by a change in capacitance from the electrode portions  24 B of the X fixed electrode  21 B is led, and this X third sensor wiring  32 B is also partially exposed as an electrode pad  4 B (not shown) in the same manner as other wirings  29 B and  30 B. 
     On the semiconductor substrate  2 B, the upper surfaces and the side surfaces of the X fixed electrode  21 B and the X movable electrode  22 B are coated together with the first insulating film  33 B and the second insulating film  34 B by a protective thin film  35 B made of silicon oxide (SiO 2 ). 
     On portions except for the cavity  10 B of the surface of the semiconductor substrate  2 B, a third insulating film  36 B, a fourth insulating film  37 B, a fifth insulating film  38 B, and a surface protective film  39 B are laminated in order on the second insulating film  34 B. 
     In the X-axis sensor  6 B structured as described above, when acceleration in the X-axis direction is applied to the X movable electrode  22 B, the beam portions  25 B expand and contract and the base portion  26 B of the X movable electrode  22 B oscillates along the surface of the semiconductor substrate  2 B, and accordingly, the electrode portions  27 B of the X movable electrode  22 B that engage with the electrode portions  24 B of the X fixed electrode  21 B like comb teeth oscillate alternately in directions approaching and away from the electrode portions  24 B of the X fixed electrode  21 B. Accordingly, the opposing distance dx between the electrode portions  24 B of the X fixed electrode  21 B and the electrode portions  27 B of the X movable electrode  22 B adjacent to each other changes. Then, by detecting a change in capacitance between the X movable electrode  22 B and the X fixed electrode  21 B caused by the change in opposing distance dx, the acceleration ax in the X-axis direction is detected. 
     In the present preferred embodiment, the acceleration ax in the X-axis direction is obtained by calculating a difference between detection values of the electrode portions on one side and the other side insulated and separated from each other of the X movable electrode  22 B. 
     In the Y-axis sensor  7 B, when acceleration in the Y-axis direction is applied to the Y movable electrode  42 B, the beam portions  45 B expand and contract and the base portion  46 B of the Y movable electrode  42 B oscillates along the surface of the semiconductor substrate  2 B, and accordingly, the electrode portions  47 B of the Y movable electrode  42 B that engage with the electrode portions  44 B of the Y fixed electrode  41 B like comb teeth oscillate alternately in directions approaching and away from the electrode portions  44 B of the Y fixed electrode  41 B. Accordingly, the opposing distance between the electrode portions  44 B of the Y fixed electrode  41 B and the electrode portions  47 B of the Y movable electrode  42 B adjacent to each other changes. Then, by detecting a change in capacitance between the Y movable electrode  42 B and the Y fixed electrode  41 B caused by the change in opposing distance, the acceleration ay in the Y-axis direction is detected. 
     &lt;Arrangement of Z-Axis Sensor&gt; 
     Next, with reference to  FIG. 10 ,  FIG. 13 , and  FIG. 14 , the arrangement of the Z-axis sensor will be described. 
       FIG. 13  is a plan view of a principal portion of the Z-axis sensor shown in  FIG. 10 .  FIG. 14  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 10 , illustrating a section taken along the cutting plane D-D in  FIG. 13 . 
     Referring to  FIG. 10 , the semiconductor substrate  2 B made of conductive silicon has the cavity  10 B inside as described above. In the upper wall  11 B (surface portion) of the semiconductor substrate  2 B, Z-axis sensors  7 B supported by the support portions  14 B while in a floating state with respect to the bottom wall  12 B of the semiconductor substrate  2 B are disposed to surround the X-axis sensor  5 B and the Y-axis sensor  6 B, respectively. 
     Each Z-axis sensor  7 B includes a Z fixed electrode  61 B as a second electrode fixed to the support portion  14 B (straight portion  16 B) provided inside the cavity  10 B, and a Z movable electrode  62 B as a first electrode held to be capable of oscillating with respect to the Z fixed electrode  61 B. The Z fixed electrode  61 B and the Z movable electrode  62 B are formed to have the same thickness. 
     In one Z-axis sensor  7 B of these two Z-axis sensors  7 B, the Z movable electrode  62 B is disposed to surround the annular portion  17 B of the support portion  14 B, and the Z fixed electrode  61 B is disposed to further surround the Z movable electrode  62 B. In the other Z-axis sensor  7 B, the Z fixed electrode  61 B is disposed to surround the annular portion  17 B of the support portion  14 B, and the Z movable electrode  62 B is disposed to further surround the Z fixed electrode  61 B. The Z fixed electrode  61 B and the Z movable electrode  62 B are connected integrally to both side walls of the straight portion  16 B of the support portion  14 B. 
     The Z fixed electrode  61 B includes a base portion  63 B that has a quadrilateral annular shape in a plan view and is fixed to the support portion  14 B, and electrode portions  64 B that are provided on the portion opposite to the straight portion  16 B with respect to the X-axis sensor  5 B (Y-axis sensor  6 B) on the base portion  63 B and aligned like comb teeth. 
     The Z movable electrode  62 B includes a base portion  65 B having a quadrilateral annular shape in a plan view, and electrode portions  66 B that extend from the base portion  65 B toward the portions between the comb-tooth-like electrode portions  64 B of the Z fixed electrode  61 B adjacent to each other, and are aligned like comb teeth so as to engage with the electrode portions  64 B of the Z fixed electrode  61 B without contact. The base portion  65 B of this Z movable electrode  62 B has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. The base portion  65 B of the Z movable electrode  62 B thus structured has sections in which the reinforcing frames are omitted at portions on the side opposite to the side of disposition of the electrode portions  66 B, and the main frames in these sections function as beam portions  67 B for enabling the Z movable electrode  62 B to move up and down. 
     Specifically, in this Z-axis sensor  7 B, the beam portions  67 B elastically warp, and the base portion  65 B of the Z movable electrode  62 B turns like a pendulum in directions approaching and away from the cavity  10 B around the beam portions  67 B as pivot points (oscillation Uz), and accordingly, the electrode portions  66 B of the Z movable electrode  62 B that engage with the electrode portions  64 B of the Z fixed electrode  61 B like comb teeth oscillate up and down. 
     The base portion  63 B of the Z fixed electrode  61 B has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     The electrode portions  64 B of the Z fixed electrode  61 B have base end portions connected to the base portion  63 B of the Z fixed electrode  61 B and tip end portions extending toward the Z movable electrode  62 B, and are aligned like comb teeth at even intervals along the inner wall of the base portion  63 B. In portions close to the base end portions of the electrode portions  64 B, insulating layers  68 B (silicon oxide in the present preferred embodiment) are embedded from the surface to the cavity  10 B across the electrode portions  64 B in the width direction. By the insulating layers  68 B, the electrode portions  64 B of the Z fixed electrode  61 B are insulated from other portions of the Z fixed electrode  61 B. 
     The electrode portions  66 B of the Z movable electrode  62 B have base end portions connected to the base portion  65 B of the Z movable electrode  62 B and tip end portions extending toward the portions between the electrode portions  64 B of the Z fixed electrode  61 B, and are aligned like comb teeth engaging with the electrode portions  64 B of the Z fixed electrode  61 B without contact. Accordingly, one electrode portion  64 B is disposed on each of one side and the other side in the width direction of each electrode portion  66 B. 
     In portions close to the base end portions of the electrode portions  66 B of the Z movable electrode  62 B, insulating layers  74 B (silicon oxide in the present preferred embodiment) are embedded from the surface to the cavity  10 B of the semiconductor substrate  2 B across the electrode portions  66 B in the width direction. By the insulating layers  74 B, the electrode portions  66 B of the Z movable electrode  62 B are insulated from other portions of the Z movable electrode  62 B. 
     In each electrode portion  66 B, from the surface of the semiconductor substrate  2 B to a point halfway in the thickness direction to the cavity  10 B, a dielectric layer  70 B (silicon oxide in the present preferred embodiment) is embedded. 
     Each dielectric layer  70 B is provided one-sided to one end side in the width direction of the electrode portion  66 B (the right side in a direction from the base end portion toward the tip end portion of each electrode portion  66 B). Accordingly, each electrode portion  66 B is partitioned into the dielectric layer  70 B provided on one end side in the width direction and a conductive layer  80 B provided on the other end side with respect to the dielectric layer  70 B (the left side in a direction from the base end portion toward the tip end portion of each electrode portion  66 B) in a plan view. 
     The conductive layer  80 B is a portion formed by using a portion of the semiconductor substrate  2 B on the electrode portion  66 B. The conductive layer  80 B integrally includes a first portion  76 B formed adjacently on the other end side in the width direction to the dielectric layer  70 B, and a second portion  78 B formed adjacently on the cavity  10 B side in the thickness direction to the dielectric layer  70 B. 
     On the surface of the semiconductor substrate  2 B including the Z fixed electrode  61 B and the Z movable electrode  62 B, as described above, the first insulating film  33 B and the second insulating film  34 B made of silicon oxide (SiO 2 ) are laminated in order. 
     On the second insulating film  34 B, a Z first sensor wiring  75 B and a Z second sensor wiring  77 B are formed. The Z first sensor wiring  75 B and the Z second sensor wiring  77 B are respectively connected to the electrode portions  64 B of the Z fixed electrode  61 B and the electrode portions  66 B (conductive layers  80 B) of the Z movable electrode  62 B adjacent to each other. 
     In detail, the Z first sensor wiring  75 B is formed along the base portion  63 B of the Z fixed electrode  61 B and includes aluminum wirings branched toward the tip end portions of the electrode portions  64 B across the insulating layers  68 B of the electrode portions  64 B of the Z fixed electrode  61 B. The branched aluminum wirings are electrically connected to the tip end sides relative to the insulating layers  68 B of the electrode portions  64 B by penetrating through the first insulating film  33 B and the second insulating film  34 B. As shown in  FIG. 10 , the Z first sensor wiring  75 B is led onto the support portion  14 B via the base portion  63 B of the Z fixed electrode  61 B, and partially exposed as electrode pads  4 B. 
     The Z second sensor wiring  77 B is formed along the base portion  65 B of the Z movable electrode  62 B, and includes aluminum wirings branched toward the electrode portions  66 B across the insulating layers  74 B close to the base end portions of the electrode portions  66 B of the Z movable electrode  62 B. The branched aluminum wirings are electrically connected to the electrode portions  66 B by penetrating through the first insulating film  33 B and the second insulating film  34 B. As shown in  FIG. 10 , the Z second sensor wiring  77 B is led onto the support portion  14 B via the base portion  65 B of the Z movable electrode  62 B, and partially exposed as electrode pads  4 B. 
     On the semiconductor substrate  2 B, the upper surfaces and side surfaces of the Z fixed electrode  61 B and the Z movable electrode  62 B are coated together with the first insulating film  33 B and the second insulating film  34 B by a protective thin film  35 B made of silicon oxide (SiO 2 ). 
     On portions other than the cavity  10 B on the surface of the semiconductor substrate  2 B, the third insulating film  36 B, the fourth insulating film  37 B, the fifth insulating film  38 B, and the surface protective film  39 B are laminated in order on the second insulating film  34 B. 
     In this Z-axis sensor  7 B, the electrode portions  64 B to which the Z first sensor wiring  75 B is connected and the conductive layers  80 B of the electrode portions  66 B to which the Z second sensor wiring  77 B is connected are opposed to each other, and constitute electrodes of a capacitor when a fixed voltage is applied between these electrodes and the capacitance changes due to a change in opposing area S. 
     When acceleration in the Z-axis direction is applied to the Z movable electrode  62 B, the comb-tooth-like Z movable electrode  62 B oscillates up and down like a pendulum similarly around the comb-tooth-like Z fixed electrode  61 B as a center of oscillation along the Z-axis direction with respect to the Z fixed electrode  61 B. Accordingly, the opposing area S between the electrode portions  64 B of the Z fixed electrode  61 B and the electrode portions  66 B of the Z movable electrode  62 B adjacent to each other changes. Then, by detecting a change in capacitance between the Z movable electrode  62 B and the Z fixed electrode  61 B caused by the change in opposing area S, the acceleration az in the Z-axis direction is detected. 
     In the present preferred embodiment, the conductive layer  80 B of each electrode portion  66 B includes a first portion  76 B opposed to the electrode portion  64 B of the Z fixed electrode  61 B via the dielectric layer  70 B and a second portion  78 B opposed to the electrode portion  64 B without interposition of the dielectric layer  70 B therebetween. 
     Therefore, in the capacitor arranged by making the electrode portions  64 B of the Z fixed electrode  61 B and the electrode portions  66 B of the Z movable electrode  62 B opposed to each other, at the portion at which the first portion  76 B of the conductive layer  80 B and the electrode portion  64 B are opposed to each other, the electrode-to-electrode distance d1 of the capacitor is larger by the width W of the dielectric layer  70 B than the electrode-to-electrode distance d2 that the capacitor originally has (the distance between the second portion  78 B of the conductive layer  80 B and the electrode portion  64 B of the Z fixed electrode  61 B) (that is, d1=d2+W). Therefore, in the same capacitor, a capacitance difference can be provided. 
     Therefore, when the Z movable electrode  62 B oscillates first to the side (upper side) away from the cavity  10 B with respect to the Z fixed electrode  61 B, the capacitance of the capacitor decreases at a decrease rate D1 (D1&gt;0) based on the electrode-to-electrode distance d1 while the first portions  76 B of the conductive layers  80 B are opposed to the electrode portions  64 B of the Z fixed electrode  61 B. Thereafter, when the first portions  76 B completely protrude above the Z fixed electrode  61 B and only the second portions  78 B of the conductive layers  80 B are opposed to the electrode portions  64 B of the Z fixed electrode  61 B, the capacitance decreases from this timing at a decrease rate D2 (D2&gt;0) based on the original electrode-to-electrode distance d2. 
     This decrease rate D2 of the capacitance is larger than the decrease rate D1 because the electrode-to-electrode distance d2 is smaller than the electrode-to-electrode distance d1 and the capacitance to decrease per unit time increases. Specifically, when the Z movable electrode  62 B starts to oscillate to the upper side, the capacitance of the capacitor decreases at the first decrease rate D1 and then decreases at the second decrease rate D2 higher than the first decrease rate D1. 
     On the other hand, when the Z movable electrode  62 B oscillates first to the side (lower side) to approach the cavity  10 B with respect to the Z fixed electrode  61 B, the capacitance of the capacitor decreases at the decrease rate D2 based on the electrode-to-electrode distance d2 until the second portions  78 B completely protrude below the Z fixed electrode  61 B. Thereafter, when the second portions  78 B completely protrude below the Z fixed electrode  61 B and only the first portions  76 B are opposed to the electrode portions  64 B of the Z fixed electrode  61 B, the capacitance decreases from this timing at the decrease rate D1 based on the electrode-to-electrode distance d1. This decrease rate D1 of the capacitance is smaller than the decrease rate D2 because the electrode-to-electrode distance d1 is larger than the electrode-to-electrode distance d2 and the capacitance to decrease per unit time becomes smaller. Specifically, when the Z movable electrode  62 B starts to oscillate to the lower side, the capacitance of the capacitor decreases at the second decrease rate D2 and then decreases at the first decrease rate D1 smaller than the second decrease rate D2. 
     Therefore, by detecting whether the capacitance of the capacitor decreases at the relatively small decrease rate D1 and then decreases at the relatively large decrease rate D2 (D1→D2) or decreases at the relatively large decrease rate D2 and then decreases at the relatively small decrease rate D1 (D2→D1), the direction in which the Z movable electrode  62 B oscillated first (the direction away from the cavity  10 B or the direction approaching the cavity  10 B) can be easily grasped. As a result, the direction of the acceleration vector can be accurately detected, so that the detection sensitivity can be improved. 
     In addition, in the present preferred embodiment, each conductive layer  80 B integrally includes the first portion  76 B and the second portion  78 B, and therefore, the conductive layers  80 B are formed in the entire thickness direction from the surface to the back surface of the Z movable electrode  62 B. Therefore, regardless of the direction of oscillation (upward or downward) of the Z movable electrode  62 B with respect to the Z fixed electrode  61 B, the opposing area S between the conductive layers  80 B of the Z movable electrode  62 B and the Z fixed electrode  61 B decreases by necessity. In detail, when the Z movable electrode  62 B oscillates to the upper side first, the opposing area between the first portions  76 B of the conductive layers  80 B and the electrode portions  64 B of the Z fixed electrode  61 B decreases, and on the other hand, when the Z movable electrode oscillates to the lower side first, the opposing area between the second portions  78 B of the conductive layers  80 B and the electrode portions  64 B of the Z fixed electrode  61 B decreases. 
     Accordingly, a change in capacitance can be detected immediately after the start of oscillation of the Z movable electrode  62 B, so that the magnitude of the acceleration vector immediately after the start of oscillation can also be detected. 
     This improvement in detection sensitivity is obtained by embedding the dielectric layers  70 B in the electrode portions  66 B of the Z movable electrode  62 B constituting the capacitor, so that the sensor structure can be prevented from becoming complicated. 
     Further, the semiconductor substrate  2 B is a conductive silicon substrate, so that even without applying a special treatment for giving conductivity to the X fixed electrode  21 B, the Y fixed electrode  41 B, and the Z fixed electrode  61 B, and the X movable electrode  22 B, the Y movable electrode  42 B, and the Z movable electrode  62 B molded into predetermined shapes, the molded structures can be used as they are as electrodes. In addition, the portions except for the portions to be used as electrodes can be used as wirings (the Z first sensor wiring  75 B, the Z second sensor wiring  77 B, etc.). 
     In the present preferred embodiment, the acceleration az in the Z-axis direction can be obtained by calculating a difference between a detection value of the Z-axis sensor  7 B surrounding the X-axis sensor  5 B and a detection value of the Z-axis sensor  7 B surrounding the Y-axis sensor  6 B. For example, as shown in  FIG. 10 , the difference can be obtained by making the position relationship of the fixed electrode and the movable electrode of the Z-axis sensor  7 B surrounding the X-axis sensor  5 B opposite to the position relationship of the fixed electrode and the movable electrode of the Z-axis sensor  7 B surrounding the Y-axis sensor  6 B. Accordingly, the manner of oscillation of the Z movable electrode  62 B differs between the pair of Z-axis sensors  7 B, so that the difference occurs. 
     &lt;Method for Manufacturing Acceleration Sensor  1 B&gt; 
     Next, the manufacturing process of the above-described acceleration sensor  1 B will be described in order of steps with reference to  FIG. 15A  to  FIG. 15G . In this paragraph, only the manufacturing process of the Z-axis sensors is shown in the drawings, and the manufacturing processes of the X-axis sensor and the Y-axis sensor are omitted, however, the manufacturing processes of the X-axis sensor and the Y-axis sensor are performed in parallel to the manufacturing process of the Z-axis sensors in the same manner as the manufacturing process of the Z-axis sensors. 
       FIG. 15A  to  FIG. 15G  are schematic sectional views showing parts of the manufacturing process of the acceleration sensor  1 B according to the second preferred embodiment of the present invention in order of steps, illustrating a section taken along the cutting plane at the same position as in  FIG. 14 . 
     To manufacture this acceleration sensor  1 B, first, as shown in  FIG. 15A , the surface of the semiconductor substrate  2 B made of conductive silicon is thermally oxidized (for example, temperature: 1100 to 1200° C., film thickness: 5000 Å). Accordingly, the first insulating film  33 B is formed on the surface of the semiconductor substrate  2 B. Next, by a known patterning technique, the first insulating film  33 B is patterned, and openings in which the dielectric layers  70 B and the insulating layers  68 B and  74 B should be embedded are formed. Next, by anisotropic deep RIE (Reactive Ion Etching) using the first insulating film  33 B as a hard mask, specifically, by a Bosch process, the semiconductor substrate  2 B is dug. Accordingly, trenches are formed in the semiconductor substrate  2 B. In the Bosch process, a step of etching the semiconductor substrate  2 B by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. Accordingly, the semiconductor substrate  2 B can be etched at a high aspect ratio, however, a wavy irregularity called scallop is formed on the etched surfaces (inner peripheral surfaces of the trenches). Subsequently, the insides of the trenches formed in the semiconductor substrate  2 B and the surface of the semiconductor substrate  2 B are thermally oxidized (for example, temperature: 1100 to 1200° C.), and then, the surface of the oxide film is etched back (for example, the film thickness after etching back is 21800 Å). Accordingly, the dielectric layers  70 B and the insulating layers  68 B and  74 B filling the trenches are formed concurrently (only the dielectric layers  70 B and the insulating layer  74 B are shown). 
     Next, as shown in  FIG. 15B , by a CVD method, the second insulating film  34 B made of silicon oxide is laminated on the semiconductor substrate  2 B. Next, the second insulating film  34 B and the first insulating film  33 B are successively etched. Accordingly, contact holes are formed in the second insulating film  34 B and the first insulating film  33 B. Next, contact plugs filling the contact holes are formed, and by sputtering, aluminum is deposited (for example, 7000 Å) on the second insulating film  34 B, and the aluminum deposit layer is patterned. Accordingly, the wirings  75 B and  77 B are formed on the second insulating film  34 B. 
     Next, as shown in  FIG. 15C , by a CVD method, the third insulating film  36 B, the fourth insulating film  37 B, the fifth insulating film  38 B, and the surface protective film  39 B are laminated in order on the second insulating film  34 B. Next, the third to fifth insulating films  36 B to  38 B and the surface protective film  39 B on the region in which the cavity  10 B of the semiconductor substrate  2 B should be formed are removed by etching. 
     Next, as shown in  FIG. 15D , a resist having openings in regions other than the regions in which the Z fixed electrode  61 B and the Z movable electrode  62 B should be formed is formed on the second insulating film  34 B. Subsequently, by anisotropic deep RIE using this resist as a mask, specifically, by a Bosch process, the semiconductor substrate  2 B is dug. Accordingly, the surface portion of the semiconductor substrate  2 B is molded into the shapes of the Z fixed electrode  61 B and the Z movable electrode  62 B, and between these, trenches  60 B are formed. In the Bosch process, a step of etching the semiconductor substrate  2 B by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. After the deep RIE, the resist is stripped. 
     Next, as shown in  FIG. 15E , by thermal oxidization or by a PECVD method, on the entire surfaces of the Z fixed electrode  61 B and the Z movable electrode  62 B and the entire inner surfaces of the trenches  60 B (that is, the side surfaces and the bottom surfaces that define the trenches  60 B), the protective thin film  35 B made of silicon oxide (SiO 2 ) is formed. 
     Next, as shown in  FIG. 15F , by etching back, the portions on the bottom surfaces of the trenches  60 B of the protective thin film  35 B are removed. Accordingly, the bottom surfaces of the trenches  60 B are exposed. 
     Next, as shown in  FIG. 15G , by anisotropic deep RIE using the surface protective film  39 B as a mask, the bottom surfaces of the trenches  60 B are further dug. Accordingly, at the bottom portions of the trenches  60 B, exposure spaces  83 B from which the crystal face of the semiconductor substrate  2 B is exposed are formed. Subsequent to this anisotropic deep RIE, by isotropic RIE, reactive ions and etching gas are supplied into the exposure spaces  83 B of the trenches  60 B. Then, by action of the reactive ions, etc., the semiconductor substrate  2 B is etched in a direction parallel to the surface of the semiconductor substrate  2 B while being etched in the thickness direction of the semiconductor substrate  2 B from the exposure spaces  83 B. Accordingly, all exposure spaces  83 B adjacent to each other are integrated together to form the cavity  10 B inside the semiconductor substrate  2 B, and inside the cavity  10 B, the Z fixed electrode  61 B and the Z movable electrode  62 B float. 
     Through these steps, the acceleration sensor  1 B (Z-axis sensor  7 B) shown in  FIG. 9  is obtained. 
     The second preferred embodiment of the present invention is described above, however the present invention can also be carried out in other embodiments. 
     For example, as shown in  FIG. 16 , each electrode portion  66 B of the Z movable electrode  62 B may have a lamination structure including a dielectric layer  81 B formed from one end to the other end in the width direction of the electrode portion  66 B and a conductive layer  82 B formed below the dielectric layer  81 B. 
     With the present arrangement, the portion from the surface or the back surface to a halfway point of the Z movable electrode  62 B is entirely formed of the dielectric layer  81 B. In this case, in the capacitor formed by making the electrode portions  64 B of the Z fixed electrode  61 B and the electrode portions  66 B of the Z movable electrode  62 B opposed to each other, at the portions at which the dielectric layers  81 B and the electrode portions  64 B of the Z fixed electrode  61 B are opposed to each other, no conductive layer opposed to the Z fixed electrode  61 B is provided, so that the capacitance becomes 0 (zero). 
     Therefore, when the Z movable electrode  62 B oscillates first to the side (upper side) away from the cavity  10 B with respect to the Z fixed electrode  61 B, the capacitance of the capacitor does not change (that is, the decrease rate D1=0) while the dielectric layers  81 B are opposed to the electrode portions  64 B of the Z fixed electrode  61 B. Thereafter, when the dielectric layers  81 B completely protrude above the Z fixed electrode  61 B and only the conductive layers  82 B are opposed to the Z fixed electrode  61 B, the capacitance decreases from this timing at the decrease rate D2 (D2&gt;0) based on the original electrode-to-electrode distance d2. 
     On the other hand, when the Z movable electrode  62 B oscillates first to the side (lower side) to approach the cavity  10 B, the capacitance of the capacitor decreases at the decrease rate D2 based on the electrode-to-electrode distance d2 while the conductive layers  82 B are opposed to the electrode portions  64 B of the Z fixed electrode  61 B. Thereafter, when the conductive layers  82 B completely protrude below the Z fixed electrode  61 B and only the dielectric layers  81 B are opposed to the Z fixed electrode  61 B, the capacitance does not change from this timing (that is, the decrease rate D1=0). 
     Therefore, with the present arrangement, the direction of the acceleration vector can be judged based on whether the decrease rate of the capacitance is 0 or not, that is, whether the capacitance changes or not. Accordingly, the acceleration can be easily detected. 
     The dielectric layers  70 B and  81 B may be made of a material other than silicon oxide as long as the material is dielectric. 
     The dielectric layers  70 B may be provided in the Z fixed electrode  61 B as shown in  FIG. 17  instead of in the Z movable electrode  62 B. Similarly, the dielectric layers  81 B may also be provided in the Z fixed electrode  61 B as shown in  FIG. 18  instead of in the Z movable electrode  62 B. 
     (3) Third Preferred Embodiment 
     Entire Arrangement of MEMS Package 
       FIG. 19  is a schematic perspective view of a MEMS package according to a third preferred embodiment of the present invention.  FIG. 20  is a sectional view of a principal portion of the MEMS package shown in  FIG. 19 , illustrating a section taken along the cutting plane E-E in  FIG. 19 . 
     The MEMS package  1 C includes a substrate  2 C, an acceleration sensor  3 C as a MEMS sensor, external terminals  4 C, an integrated circuit  5 C (ASIC: Application Specific Integrated Circuit), and a resin package  6 C. 
     The substrate  2 C is formed to have a rectangular plate shape having a surface  7 C and a back surface  8 C. 
     The acceleration sensor  3 C is disposed on one end portion in the longitudinal direction on the surface  7 C side of the substrate  2 C. The acceleration sensor  3 C includes abase substrate  9 C as a semiconductor substrate formed of a Si substrate having a square plate shape. 
     The base substrate  9 C has a sensor region  10 C and a pad region  11 C (peripheral region) surrounding the sensor region  10 C. 
     In the sensor region  10 C, as sensors that detect respective accelerations around three axes orthogonal to each other in a three-dimensional space, an X-axis sensor  12 C, a Y-axis sensor  13 C, and Z-axis sensors  14 C are provided. In the present preferred embodiment, the two directions orthogonal to each other along the surface  7 C of the substrate  2 C are defined as the X-axis direction and the Y-axis direction, and a direction along the thickness direction of the substrate  2 C orthogonal to these X-axis and Y-axis directions is defined as the Z-axis direction. 
     In the pad region  11 C, electrode pads  15 C for supplying voltages to the X-axis sensor  12 C, the Y-axis sensor  13 C, and the Z-axis sensor  14 C, respectively, are formed. A plurality (seven in  FIG. 19 ) of electrode pads  15 C are provided at even intervals along the width direction orthogonal to the longitudinal direction of the substrate  2 C. 
     The sensor region  10 C and the pad region  11 C are covered by a protective layer  16 C made of SiO 2  as a first inorganic material and formed on the base substrate  9 C. 
     The protective layer  16 C is formed to have a mesa shape integrally including a flat top portion  18 C (central portion) opposed to the sensor region  10 C via a space  17 C, a flat bottom portion  19 C (peripheral edge portion) surrounding the top portion  18 C and bonded to the pad region  11 C, and an inclined portion  20 C inclined from the entire circumference of the peripheral edge of the top portion  18 C toward the bottom portion  19 C. Between the top portion  18 C and the bottom portion  19 C of the protective layer  16 C, a level difference with a predetermined height L is provided. 
     In the top portion  18 C of the protective layer  16 C, a large number of through holes  21 C that make communication between the inside and the outside of the space  17 C are formed in a matrix. 
     On the bottom portion  19 C of the protective layer  16 C, pad openings  22 C for exposing the respective electrode pads  15 C are formed as many as the electrode pads  15 C. In the present preferred embodiment, the arrangement in which the bottom portion  19 C of the protective layer  16 C is bonded to the pad region  11 C includes an idea that the bottom portion  19 C of the protective layer  16 C is in close contact with the surface of the base substrate  9 C (meaning the uppermost surface of the base substrate  9 C, and meaning the uppermost surface of an insulating film when the insulating film such as a surface protective film is formed on the base substrate  9 C). 
     A plurality (twelve in  FIG. 19 ) of the external terminals  4 C are provided at even intervals along the width direction of the substrate  2 C on the other end portion in the longitudinal direction of the substrate  2 C (the end portion on the side opposite to the acceleration sensor  3 C). Each external terminal  4 C is formed to penetrate through the substrate  2 C in the thickness direction, and is exposed as an internal pad  23 C to the surface  7 C of the substrate  2 C, and exposed as an external pad  24 C to the back surface  8 C of the substrate  2 C. 
     The integrated circuit  5 C is disposed between the acceleration sensor  3 C and the external terminals  4 C (internal pads  23 C) on the surface  7 C side of the substrate  2 C. The integrated circuit  5 C is formed of, for example, a Si substrate having a rectangular plate shape long in the width direction of the substrate  2 C. Inside the Si substrate, charge amplifiers that amplify electric signals output from the sensors  12 C to  14 C, filter circuits (low-pass filter: LPF, etc.) that extract specific frequency components of the electric signals, and logic circuits that carry out logic operations of filtered electric signals, etc., are formed. These circuits consist of, for example, CMOS devices. The integrated circuit  5 C includes first electrode pads  25 C and second electrode pads  26 C. 
     A plurality (seven in  FIG. 19 ) of the first electrode pads  25 C are provided at even intervals along the width direction of the substrate  2 C on the end portion on the side close to the acceleration sensor  3 C in the longitudinal direction of the substrate  2 C. The first electrode pads  25 C are connected one-to-one to the electrode pads  15 C of the acceleration sensor  3 C by bonding wires  27 C. 
     A plurality (twelve in  FIG. 19 ) of the second electrode pads  26 C are provided at even intervals along the width direction of the substrate  2 C on an end portion on the side close to the external terminals  4 C in the longitudinal direction of the substrate  2 C. The second electrode pads  26 C are connected one-to-one to the internal pads  23 C of the external terminals  4 C by bonding wires  28 C. 
     The resin package  6 C defines the external shape of the MEMS package  1 C in cooperation with the substrate  2 C, and is formed to have a substantially rectangular parallelepiped shape. The resin package  6 C is made of, for example, a known molding resin such as epoxy resin, and seals the acceleration sensor  3 C and the integrated circuit  5 C so as to cover the bonding wires  27 C and  28 C and the internal pads  23 C as well as the acceleration sensor  3 C and the integrated circuit  5 C, and expose the external pads  24 C. 
     &lt;Arrangement of X-Axis Sensor and Y-Axis Sensor&gt; 
     Next, with reference to  FIG. 21  to  FIG. 23 , the arrangement of the X-axis sensor and the Y-axis sensor will be described. 
       FIG. 21  is a schematic plan view of the acceleration sensor shown in  FIG. 19 .  FIG. 22  is a plan view of a principal portion of the X-axis sensor shown in  FIG. 21 .  FIG. 23  is a sectional view of a principal portion of the X-axis sensor shown in  FIG. 21 , illustrating a section taken along the cutting plane F-F in  FIG. 22 . 
     The acceleration sensor  3 C includes the base substrate  9 C formed of a Si substrate as described above. This base substrate  9 C has a cavity  29 C inside, and in the upper wall  30 C as a surface layer portion of the base substrate  9 C having a ceiling that partitions the cavity  29 C from the surface side, the X-axis sensor  12 C, the Y-axis sensor  13 C, and the Z-axis sensors  14 C are formed. Specifically, the X-axis sensor  12 C, the Y-axis sensor  13 C, and the Z-axis sensors  14 C are formed of portions of the base substrate  9 C, and are supported while in a floating state with respect to the bottom wall  31 C of the base substrate  9 C that has a bottom surface partitioning the cavity  29 C from the back surface side. 
     The X-axis sensor  12 C and the Y-axis sensor  13 C are disposed adjacent to each other at an interval. The Z-axis sensors  14 C are disposed to surround the X-axis sensor  12 C and the Y-axis sensor  13 C, respectively. 
     In the present preferred embodiment, the Y-axis sensor  13 C has an arrangement that is substantially the same as an arrangement obtained by rotating 90 degrees the X-axis sensor  12 C in a plan view. Therefore, hereinafter, instead of a detailed description of the arrangement of the Y-axis sensor  13 C, in the description of the portions of the X-axis sensor  12 C, portions of the Y-axis sensor corresponding to the portions of the X-axis sensor are also described with parentheses. 
     Between the X-axis sensor  12 C and the Z-axis sensor  14 C and between the Y-axis sensor  13 C and the Z-axis sensor  14 C, support portions  32 C for supporting these sensors in a floating state are formed. 
     The support portions  32 C integrally include straight portions  34 C extending across the Z-axis sensors  14 C toward the X-axis sensor  12 C and the Y-axis sensor  13 C from one side wall  33 C having side surfaces partitioning the cavity  29 C of the base substrate  9 C from the lateral sides, and annular portions  35 C surrounding the X-axis sensor  12 C and the Y-axis sensor  13 C. 
     The X-axis sensor  12 C and the Y-axis sensor  13 C are disposed inside the annular portions  35 C, and both ends of these sensors are supported at two points opposing each other on the inner walls of the annular portions  35 C. Both ends of the Z-axis sensors  14 C are supported by both side walls of the straight portions  34 C. 
     The X-axis sensor  12 C (Y-axis sensor  13 C) has an X fixed electrode  41 C (Y fixed electrode  61 C) and an X movable electrode  42 C (Y movable electrode  62 C) that are formed to have the same thickness with respect to each other. 
     The X fixed electrode  41 C (Y fixed electrode  61 C) includes a first base portion  43 C (first base portion  63 C of the Y fixed electrode  61 C) having a quadrilateral annular shape in a plan view fixed to the support portion  32 C, and a plurality of pairs of first comb tooth portions  44 C (first comb tooth portions  64 C of the Y fixed electrode  61 C) aligned like comb teeth at even intervals along the inner wall of the first base portion  43 C. 
     The first base portion  43 C of the X fixed electrode  41 C has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     As the first comb tooth portions  44 C of the X fixed electrode  41 C, two electrode portions straight in a plan view and having base end portions connected to the first base portion  43 C and tip end portions thereof opposed to each other are paired, and a plurality of pairs of the electrode portions are provided at even intervals. Each first comb tooth portion  44 C has a framed structure that has a ladder-like shape in a plan view and includes straight main frames extending parallel to each other and a plurality of traverse frames laid across the main frames. 
     The X movable electrode  42 C (Y movable electrode  62 C) is held to be capable of oscillating with respect to the X fixed electrode  41 C. 
     The X movable electrode  42 C (Y movable electrode  62 C) includes a second base portion  45 C (second base portion  65 C of the Y movable electrode  62 C) and second comb tooth portions  46 C (second comb tooth portions  66 C of the Y movable electrode  62 C). 
     The second base portion  45 C of the X movable electrode  42 C is formed of a plurality (six in the present preferred embodiment) of straight frames extending parallel to each other along a direction across the first comb tooth portions  44 C of the X fixed electrode  41 C. Both ends of the second base portion  45 C are connected to beam portions  47 C (beam portions  67 C of the Y movable electrode  62 C) capable of expanding and contracting along the direction across the first comb tooth portions  44 C. 
     Two beam portions  47 C are provided on each of the ends of the second base portion  45 C of the X movable electrode  42 C. 
     The second comb tooth portions  46 C of the X movable electrode  42 C extend from the second base portion  45 C to both sides toward the portions between the first comb tooth portions  44 C of the X fixed electrode  41 C adjacent to each other, and are aligned like comb teeth that engage with the first comb tooth portions  44 C of the X fixed electrode  41 C without contact therebetween. Each second comb tooth portion  46 C has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other across the frames of the second base portion  45 C and a plurality of traverse frames laid across the main frames. 
     In the X movable electrode  42 C, on lines halving the second comb tooth portions  46 C in a direction orthogonal to the oscillation direction Ux, insulating layers  48 C across the traverse frames are embedded from the surface to the cavity  29 C. 
     The insulating layers  48 C are made of SiO 2  (silicon oxide). Each second comb tooth portion  46 C is insulated and separated into two of one side and the other side along the oscillation direction Ux by the insulating layers  48 C. Accordingly, the separated second comb tooth portions  46 C of the X movable electrode  42 C function as respective independent electrodes in the X movable electrode  42 C. 
     On the surface of the base substrate  9 C including the X fixed electrode  41 C and the X movable electrode  42 C, a first insulating film  49 C and a second insulating film  50 C made of silicon oxide (SiO 2 ) are laminated in order. 
     Between the first insulating film  49 C and the second insulating film  50 C, an X first detection wiring  51 C (Y first detection wiring  71 C) and an X second detection wiring  52 C (Y second detection wiring  72 C) are formed. 
     The X first detection wiring  51 C detects a change in voltage accompanying a change in capacitance from one side (in the present preferred embodiment, the left side on the paper surface shown in  FIG. 21 ) of each second comb tooth portion  46 C insulated and separated into two. 
     The X second detection wiring  52 C detects a change in voltage accompanying a change in capacitance from the other side (in the present preferred embodiment, the right side on the paper surface shown in  FIG. 21 ) of each second comb tooth portion  46 C insulated and separated into two. 
     The X first detection wiring  51 C and the X second detection wiring  52 C are made of aluminum (Al) in the present preferred embodiment. The X first detection wiring  51 C and the X second detection wiring  52 C are electrically connected to the second comb tooth portions  46 C by penetrating through the first insulating film  49 C. 
     The X first detection wiring  51 C and the X second detection wiring  52 C are led onto the support portion  32 C via the beam portions  47 C of the X movable electrode  42 C and the first base portion  43 C of the X fixed electrode  41 C, and partially exposed as electrode pads  15 C. 
     The X first detection wiring  51 C and the X second detection wiring  52 C use the beam portions  47 C themselves formed of portions of the conductive base substrate  9 C as current paths in sections passing through the beam portions  47 C of the respective X movable electrode  42 C. No aluminum wiring is provided on the beam portions  47 C, so that the expandability of the beam portions  47 C can be maintained. 
     To the support portion  32 C, an X third detection wiring  53 C (Y third detection wiring  73 C) that detects a change in voltage accompanying a change in capacitance from the first comb tooth portions  44 C of the X fixed electrode  41 C is led. The X third detection wiring  53 C is also partially exposed as an electrode pad  15 C (not shown) in the same manner as other wirings  51 C and  52 C. 
     The upper surfaces and side surfaces of the X fixed electrode  41 C and the X movable electrode  42 C are coated by a protective thin film  54 C made of SiO 2  so that the first insulating film  49 C and the second insulating film  50 C are covered. 
     In the X-axis sensor  12 C structured as described above, the first comb tooth portions  44 C (X fixed electrode  41 C) to which the X third detection wiring  53 C is connected and the second comb tooth portions  46 C (X movable electrode  42 C) to which the X first detection wiring  51 C and the X second detection wiring  52 C are connected are opposed to each other at an electrode-to-electrode distance d x  to constitute a capacitor. 
     Then, when acceleration in the X-axis direction is applied to the X movable electrode  42 C, the beam portions  47 C expand and contract and the second base portion  45 C of the X movable electrode  42 C oscillates along the surface of the base substrate  9 C. Accordingly, the second comb tooth portions  46 C of the X movable electrode  42 C that engage with the first comb tooth portions  44 C of the X fixed electrode  41 C like comb teeth oscillate alternately in directions approaching and away from the first comb tooth portions  44 C of the X fixed electrode  41 C. 
     As a result, the electrode-to-electrode distance d x  between the first comb tooth portions  44 C of the X fixed electrode  41 C and the second comb tooth portions  46 C of the X movable electrode  42 C adjacent to each other changes. Then, by detecting a change in capacitance between the X movable electrode  42 C and the X fixed electrode  41 C caused by the change in electrode-to-electrode distance d x , the acceleration a x  in the X-axis direction is detected. 
     In the present preferred embodiment, the acceleration a x  in the X-axis direction is obtained by calculating a difference between detection values of one side and the other side electrode portions insulated and separated from each other of the X movable electrode  42 C. 
     In the Y-axis sensor  13 C, when acceleration in the Y-axis direction is applied to the Y movable electrode  62 C, the beam portions  67 C expand and contract and the second base portion  65 C of the Y movable electrode  62 C oscillates along the surface of the base substrate  9 C. Accordingly, the second comb tooth portions  66 C of the Y movable electrode  62 C that engage with the first comb tooth portions  64 C of the Y fixed electrode  61 C like comb teeth oscillate alternately in directions approaching and away from the first comb tooth portions  64 C of the Y fixed electrode  61 C. 
     As a result, the electrode-to-electrode distance d y  between the first comb tooth portions  64 C of the Y fixed electrode  61 C and the second comb tooth portions  66 C of the Y movable electrode  62 C adjacent to each other changes. Then, by detecting a change in capacitance between the Y movable electrode  62 C and the Y fixed electrode  61 C caused by the change in electrode-to-electrode distance d y , the acceleration a y  in the Y-axis direction is detected. 
     &lt;Arrangement of Z-Axis Sensor&gt; 
     Next, an arrangement of the Z-axis sensor will be described with reference to  FIG. 21 ,  FIG. 24 , and  FIG. 25 . 
       FIG. 24  is a plan view of a principal portion of the Z-axis sensor shown in  FIG. 21 .  FIG. 25  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 21 , illustrating a section taken along the cutting plane G-G in  FIG. 24 . 
     The Z-axis sensors  14 C are disposed to surround the X-axis sensor  12 C and the Y-axis sensor  13 C, respectively, as described above. 
     The Z-axis sensor  14 C includes a Z fixed electrode  81 C and a Z movable electrode  82 C formed to have the same thickness and the same width with respect to each other. In  FIG. 24  and  FIG. 25 , the thickness and the width of the Z fixed electrode  81 C are the thickness T 1  and the width W 1 , respectively, and the thickness and the width of the Z movable electrode  82 C are the thickness T 2  and the width W 2 , respectively. 
     The Z fixed electrode  81 C is fixed to the support portion  32 C (straight portion  34 C) provided inside the cavity  29 C. 
     The Z movable electrode  82 C is held to be capable of oscillating with respect to the Z fixed electrode  81 C. 
     In the present preferred embodiment, in one Z-axis sensor  14 C of the two Z-axis sensors  14 C, the Z movable electrode  82 C is disposed to surround the annular portion  35 C, and the Z fixed electrode  81 C is disposed to surround the Z movable electrode  82 C. 
     In the other Z-axis sensor  14 C, the Z fixed electrode  81 C is disposed to surround the annular portion  35 C, and the Z movable electrode  82 C is disposed to surround the Z fixed electrode  81 C. 
     In each Z-axis sensor  14 C, the Z fixed electrode  81 C includes a first base portion  83 C and a plurality of first comb tooth portions  84 C. 
     The first base portion  83 C of the Z fixed electrode  81 C is formed to have a quadrilateral annular shape in a plan view and fixed to the support portion  32 C. The first base portion  83 C has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     The first comb tooth portions  84 C of the Z fixed electrode  81 C are aligned like comb teeth at even intervals along the inner wall of the first base portion  83 C on the portion on the side opposite to the straight portion  34 C with respect to the X-axis sensor  12 C (Y-axis sensor  13 C) in the first base portion  83 C. 
     The first comb tooth portions  84 C have base end portions connected to the first base portion  83 C of the Z fixed electrode  81 C, and tip end portions extending toward the Z movable electrode  82 C. In portions close to the base end portions of the first comb tooth portions  84 C, insulating layers  85 C as first insulating layers across the first comb tooth portions  84 C in the width direction are embedded from the surface to the cavity  29 C. 
     The insulating layers  85 C are made of SiO 2 . The first comb tooth portions  84 C are insulated from other portions of the Z fixed electrode  81 C by the insulating layers  85 C. 
     In each Z-axis sensor  14 C, the Z movable electrode  82 C includes a second base portion  86 C and second comb tooth portions  87 C. 
     The second base portion  86 C of the Z movable electrode  82 C is formed to have a quadrilateral annular shape in a plan view. In addition, the second base portion  86 C has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     The second base portion  86 C having the framed structure has sections in which the reinforcing frames are omitted at portions on the side opposite to the disposition of the second comb tooth portions  87 C. The main frames in these omitted sections function as beam portions  88 C for enabling the Z movable electrode  82 C to move up and down. 
     The second comb tooth portions  87 C of the Z movable electrode  82 C extend from the second base portion  86 C toward the portions between the first comb tooth portions  84 C adjacent to each other of the Z fixed electrode  81 C, and aligned like comb teeth to engage with the first comb tooth portions  84 C without contact. 
     The second comb tooth portions  87 C have base end portions connected to the second base portion  86 C of the Z movable electrode  82 C, and tip end portions extending toward the portions between the first comb tooth portions  84 C of the Z fixed electrode  81 C. 
     In portions close to the base end portions of the second comb tooth portions  87 C, insulating layers  89 C as second insulating layers across the second comb tooth portions  87 C in the width direction are embedded from the surface to the cavity  29 C of the base substrate  9 C. 
     The insulating layers  89 C are made of SiO 2 . The second comb tooth portions  87 C are insulated from other portions of the Z movable electrode  82 C by the insulating layers  89 C. 
     On the surface of the base substrate  9 C including the Z fixed electrode  81 C and the Z movable electrode  82 C, as described above, a first insulating film  49 C and a second insulating film  50 C made of SiO 2  are laminated in order. 
     Between the first insulating film  49 C and the second insulating film  50 C, a Z first detection wiring  90 C and a Z second detection wiring  91 C are formed. 
     The Z first detection wiring  90 C and the Z second detection wiring  91 C are respectively connected to the first comb tooth portions  84 C of the Z fixed electrode  81 C and the second comb tooth portions  87 C of the Z movable electrode  82 C adjacent to each other. 
     In detail, the Z first detection wiring  90 C is formed along the first base portion  83 C, and includes Al wirings branched toward the tip end portions of the first comb tooth portions  84 C across the insulating layers  85 C of the first comb tooth portions  84 C. 
     The branched Al wirings are electrically connected to the tip end sides relative to the insulating layers  85 C of the first comb tooth portions  84 C by penetrating through the first insulating film  49 C. 
     As shown in  FIG. 21 , the Z first detection wiring  90 C is led onto the support portion  32 C via the first base portion  83 C, and partially exposed as an electrode pad  15 C. 
     The Z second detection wiring  91 C is formed along the second base portion  86 C, and includes Al wirings branched toward the second comb tooth portions  87 C across the insulating layers  89 C close to the base end portions of the second comb tooth portions  87 C. 
     The branched Al wirings are electrically connected to the second comb tooth portions  87 C by penetrating through the first insulating film  49 C. 
     As shown in  FIG. 21 , the Z second detection wiring  91 C is led onto the support portion  32 C via the second base portion  86 C, and partially exposed as an electrode pad  15 C. 
     The upper surfaces and side surfaces of Z fixed electrode  81 C and the Z movable electrode  82 C are coated by a protective thin film  54 C made of SiO 2  so that the first insulating film  49 C and the second insulating film  50 C are covered. 
     In the Z-axis sensor  14 C structured as described above, the first comb tooth portions  84 C (Z fixed electrode  81 C) to which the Z first detection wiring  90 C is connected and the second comb tooth portions  87 C (Z movable electrode  82 C) to which the Z second detection wiring  91 C is connected are opposed at an electrode-to-electrode distance d z  to constitute a capacitor. 
     When acceleration in the Z-axis direction is applied to the Z movable electrode  82 C, the comb-tooth-like Z movable electrode  82 C oscillates up and down like a pendulum similarly around the comb-tooth-like Z fixed electrode  81 C as a center of oscillation along the Z-axis direction with respect to the Z fixed electrode  81 C. 
     Accordingly, the opposing area S between the first comb tooth portions  84 C of the Z fixed electrode  81 C and the second comb tooth portions  87 C of the Z movable electrode  82 C adjacent to each other changes. Then, by detecting a change in capacitance between the Z movable electrode  82 C and the Z fixed electrode  81 C caused by the change in opposing area S, the acceleration a z  in the Z-axis direction is detected. 
     In the present preferred embodiment, the acceleration a z  in the Z-axis direction is obtained by calculating a difference between a detection value of the Z-axis sensor  14 C surrounding the X-axis sensor  12 C and a detection value of the Z-axis sensor  14 C surrounding the Y-axis sensor  13 C. 
     For example, as shown in  FIG. 21 , the difference can be obtained by making the position relationship between the fixed electrode and the movable electrode of the Z-axis sensor  14 C surrounding the X-axis sensor  12 C opposite to the position relationship between the fixed electrode and the movable electrode of the Z-axis sensor  14 C surrounding the Y-axis sensor  13 C. Accordingly, the manner of oscillation of the Z movable electrode  82 C differs between the pair of Z-axis sensors  14 C, so that the difference occurs. 
     &lt;Method for Manufacturing Acceleration Sensor&gt; 
     Next, the manufacturing process of the above-described acceleration sensor will be described with reference to  FIG. 26A  to  FIG. 26M  in order of steps. In this paragraph, only the manufacturing process of the Z-axis sensors is shown in the drawings, and the description of the manufacturing processes of the X-axis sensor and the Y-axis sensor are omitted, however, the manufacturing processes of the X-axis sensor and the Y-axis sensor are performed in the same manner as the manufacturing process of the Z-axis sensors in parallel to the manufacturing process of the Z-axis sensors. 
       FIG. 26A  to  FIG. 26M  are schematic sectional views showing parts of the manufacturing process of the Z-axis sensors shown in  FIG. 21  in order of steps, illustrating a cutting plane taken at the same position as in  FIG. 25 . 
     To manufacture the Z-axis sensors  14 C, as shown in  FIG. 26A , the surface of the base substrate  9 C made of conductive silicon is thermally oxidized (for example, temperature: 1100 to 1200° C., film thickness: 5000 Å). Accordingly, the first insulating film  49 C is formed on the surface of the base substrate  9 C. 
     Next, by a known patterning technique, the first insulating film  49 C is patterned, and openings are formed in regions in which the insulating layers  85 C and  89 C should be embedded. Next, by anisotropic deep RIE (Reactive Ion Etching) using the first insulating film  49 C as a hard mask, specifically, by a Bosch process, the base substrate  9 C is dug. Accordingly, trenches  36 C are formed in the base substrate  9 C. 
     In the Bosch process, a step of etching the base substrate  9 C by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. Accordingly, the base substrate  9 C can be etched at a high aspect ratio, however, a wavy irregularity called scallop is formed on the etched surfaces (inner peripheral surfaces of the trenches). 
     Next, as shown in  FIG. 26B , the insides of the trenches  36 C formed in the base substrate  9 C and the surface of the base substrate  9 C are thermally oxidized (for example, temperature: 1100 to 1200° C.), and then, the surface of the oxide film is etched back (for example, the film thickness after etching back of the first insulating film  49 C is 21800 Å). Accordingly, the insulating layers  85 C and  89 C filling the trenches are formed concurrently (only the insulating layer  89 C is shown). 
     Next, as shown in  FIG. 26C , the first insulating film  49 C is etched. Accordingly, contact holes are formed in the first insulating film  49 C. Next, contact plugs filling the contact holes are formed, and then, by sputtering, aluminum is deposited (for example, 7000 Å) on the first insulating film  49 C, and this aluminum deposit layer is patterned. Accordingly, on the first insulating film  49 C, the Z first detection wiring  90 C and the Z second detection wiring  91 C are formed. At this time, the electrode pads  15 C are also formed on the first insulating film  49 C concurrently although this is not shown. 
     Next, as shown in  FIG. 26D , by a CVD method, the second insulating film  50 C is laminated on the first insulating film  49 C. Next, the second insulating film  50 C and the first insulating film  49 C on regions in which the cavity  29 C of the base substrate  9 C should be formed are removed in order by etching. By etching the second insulating film  50 C, openings for exposing the electrode pads  15 C are formed in the second insulating film  50 C although this is not shown. 
     Subsequently, a resist having openings in regions other than the regions in which the Z fixed electrode  81 C and the Z movable electrode  82 C should be formed is formed on the second insulating film  50 C. Subsequently, by anisotropic deep RIE using the resist as a mask, specifically, by a Bosch process, the base substrate  9 C is dug. Accordingly, the surface portion of the base substrate  9 C is molded into the shapes of the Z fixed electrode  81 C and the Z movable electrode  82 C, and between these, the trenches  37 C are formed. 
     Next, as shown in  FIG. 26E , by thermal oxidization or by a PECVD method, on the entire surfaces of the Z fixed electrode  81 C and the Z movable electrode  82 C and the entire inner surfaces of the trenches  37 C (that is, the side surfaces and the bottom surfaces defining the trenches  37 C), a protective thin film  54 C made of SiO 2  is formed. 
     Next, as shown in  FIG. 26F , the portions on the bottom surfaces of the trenches  37 C of the protective thin film  54 C are removed by etching back. Accordingly, the bottom surfaces of the trenches  37 C are exposed. 
     Next, as shown in  FIG. 26G , by anisotropic deep RIE using the remaining protective thin film  54 C as a mask, the bottom surfaces of the trenches  37 C are further dug. Accordingly, at the bottom portions of the trenches  37 C, exposure spaces  38 C as recesses to which the crystal face of the base substrate  9 C is exposed are formed. 
     Next, as shown in  FIG. 26H , by a PECVD method, SiN as a second inorganic material is deposited on the entire surface of the base substrate  9 C (the entire region including the sensor region  10 C and the pad region  11 C) from above. Accordingly, a first sacrifice layer  39 C (for example, thickness: 1 μm to 5 μm) that fills the upper portions of the exposure spaces  38 C and covers the entire region including the sensor region  10 C and the pad region  11 C is formed. Accordingly, the opening ends of the exposure spaces  38 C are closed by the first sacrifice layer  39 C and the lower portions of the exposure spaces  38 C are kept hollow. 
     Next, as shown in  FIG. 26I , by sputtering, Al as a metal material is deposited on the entire surface of the first sacrifice layer  39 C (the entire region including the sensor region  10 C and the pad region  11 C) from above the base substrate  9 C. Accordingly, a second sacrifice layer  40 C (for example, thickness: 1 μm to 5 μm) thicker than the first sacrifice layer  39 C is formed on the first sacrifice layer  39 C. 
     Subsequently, by a known patterning technique, the portions above the pad region  11 C (not shown) in the second sacrifice layer  40 C and the first sacrifice layer  39 C are removed in order. 
     Next, as shown in  FIG. 26J , by a PECVD method, SiO 2  as a first inorganic material is deposited on the entire region of the base substrate  9 C (the entire region including the sensor region  10 C and the pad region  11 C) from above. Accordingly, a protective layer  16 C that adheres to the pad region  11 C exposed from the first sacrifice layer  39 C and the second sacrifice layer  40 C (specifically, the protective thin film  54 C formed on the base substrate  9 C) and covers the second sacrifice layer  40 C is formed. 
     Next, as shown in  FIG. 26K , by a known patterning technique, a large number of through holes  21 C are formed in the top portion  18 C of the protective layer  16 C. 
     Next, as shown in  FIG. 26L , a fluorine-based gas (for example, NF 3 , SF 6 , XeF 2 , etc.) as an etching medium is supplied to the second sacrifice layer  40 C via the through holes  21 C. Accordingly, the second sacrifice layer  40 C is removed by etching. Accordingly, a space  17 C is formed directly below the protective layer  16 C. 
     Next, as shown in  FIG. 26M , a chlorine-based gas (for example, Cl 2 , HCl, BCl 3 , etc.) as an etching medium is supplied to the first sacrifice layer  39 C via the through holes  21 C. Accordingly, the first sacrifice layer  39 C is removed by etching. Accordingly, the opening ends of the exposure spaces  38 C closed by the first sacrifice layer  39 C, are opened. 
     Thereafter, via the through holes  21 C, reactive ions and an etching gas are supplied into the exposure spaces  38 C of the trenches  37 C. Then, by action of the reactive ions, etc., the base substrate  9 C is etched in a direction parallel to the surface of the base substrate  9 C while being etched in the thickness direction of the base substrate  9 C from the exposure spaces  38 C. Accordingly, all exposure spaces  38 C adjacent to each other are integrated together to form a cavity  29 C inside the base substrate  9 C, and inside the cavity  29 C, the Z fixed electrode  81 C and the Z movable electrode  82 C float. 
     Through these steps, the Z-axis sensor  14 C shown in  FIG. 19  is obtained. 
     According to the above-described method, by forming the protective layer  16 C made of SiO 2  on the base substrate  9 C in which the Z fixed electrode  81 C and the Z movable electrode  82 C are formed, a layer that protects the sensor region  10 C can be formed without using a bonding material such as glass frit. Therefore, the cost for forming the protective layer  16 C can be reduced. 
     Concerning operability of formation of the protective layer  16 C, the protective layer  16 C can be formed more easily than in the case where a lid substrate is bonded by using a bonding material. 
     In detail, according to the present preferred embodiment, the first sacrifice layer  39 C made of SiN is formed by a PECVD method to cover the sensor region  10 C in which the Z fixed electrode  81 C and the Z movable electrode  82 C are formed (the step of  FIG. 26H ), and the second sacrifice layer  40 C made of Al is formed by sputtering to cover the first sacrifice layer  39 C (the step of  FIG. 26I ). Then, by a known patterning technique (photolithography), these sacrifice layers  39 C and  40 C are patterned. Next, a protective layer  16 C made of SiO 2  is formed by a PECVD method to cover the patterned sacrifice layers  39 C and  40 C. Thereafter, by a known patterning technique, the through holes  21 C are formed in the top portion  18 C of the protective layer  16 C, and by supplying a fluorine-based etching gas and a chlorine-based etching gas in order via the through holes  21 C, the second sacrifice layer  40 C and the first sacrifice layer  39 C directly below the protective layer  16 C are removed in order. Accordingly, the space  17 C is formed at the portion at which the second sacrifice layer  40 C existed, and the protective layer  16 C that covers the Z fixed electrode  81 C and the Z movable electrode  82 C via the space  17 C with respect to the sensor region  10 C is formed. 
     Therefore, without operations of position alignment of wafers, etc., by combining known semiconductor device manufacturing techniques (a PECVD method, sputtering, photolithography, and etching), the protective layer  16 C can be easily formed. 
     In addition, when forming the sacrifice layers  39 C and  40 C for forming the space  17 C between the sensor region  10 C and the protective layer  16 C, the cavity  29 C is not formed directly below the Z fixed electrode  81 C and the Z movable electrode  82 C, and these lower portions of the electrodes  81 C and  82 C are fixed integrally to the base substrate  9 C. Therefore, even if the sacrifice layers  39 C and  40 C come into contact with the Z fixed electrode  81 C and the Z movable electrode  82 C, the electrodes  81 C and  82 C are not oscillated by the impact of this contact. Therefore, it is not necessary to add a step, etc., for protecting the electrodes  81 C and  82 C from the sacrifice layers  39 C and  40 C, so that the process can be prevented from becoming complicated. 
     In the present preferred embodiment, the space  17 C is formed between the protective layer  16 C and the sensor region  10 C by etching the second sacrifice layer  40 C made of Al. Specifically, what (second sacrifice layer  40 C) is to be removed by etching is made of Al, and what (protective layer  16 C) is to be left even after etching is made of SiO 2 . Accordingly, when forming the space  17 C, the etching selectivity of the protective layer  16 C to the second sacrifice layer  40 C can be increased. 
     Therefore, even if the protective layer  16 C is exposed to a fluorine-based etching gas to be used for removing the second sacrifice layer  40 C for a long period of time, the fluorine-based etching gas is for etching Al, and therefore, erosion of the protective layer  16 C made of SiO 2  can be reduced. Therefore, the shape of the protective layer  16 C can be excellently maintained. 
     On the other hand, in the case where the second sacrifice layer  40 C made of Al is used as a sacrifice layer that closes the opening ends of the exposure spaces  38 C, if the second sacrifice layer  40 C remains on the Z fixed electrode  81 C and/or the Z movable electrode  82 C, this second sacrifice layer  40 C may cause an operation failure of the sensor. For example, if the second sacrifice layer  40 C remains across the Z fixed electrode  81 C and the Z movable electrode  82 C, a short-circuit occurs between the Z fixed electrode  81 C and the Z movable electrode  82 C via this second sacrifice layer  40 C. 
     Therefore, in the present preferred embodiment, as the sacrifice layer that closes the opening ends of the exposure spaces  38 C, the first sacrifice layer  39 C made of SiN is used. Accordingly, while the etching selectivity of the protective layer  16 C to the first sacrifice layer  39 C is secured, operation failures of the sensor can be prevented from occurring due to the sacrifice layer remaining. 
     According to the present preferred embodiment, on the entire surfaces of the Z fixed electrode  81 C and the Z movable electrode  82 C and the entire inner surfaces of the trenches  37 C, the protective thin film  54 C made of SiO 2  having etching selectivity to the sacrifice layers  39 C and  40 C is formed. Therefore, when the sacrifice layers  39 C and  40 C are removed by etching, even if the etching gas comes into contact with the side walls of the Z fixed electrode  81 C and the Z movable electrode  82 C, erosion (damage) of the Z fixed electrode  81 C and the Z movable electrode  82 C can be reduced. As a result, the variation in size (thicknesses T 1  and T 2  and the widths W 1  and W 2 ) of the Z fixed electrode  81 C and the Z movable electrode  82 C can be reduced. 
     In the acceleration sensor  3 C obtained by the above-described method, the Z fixed electrode  81 C and the Z movable electrode  82 C are covered by the top portion  18 C of the protective layer  16 C. Accordingly, dust, etc., can be prevented from entering the inside of the protective layer  16 C from the outside of the protective layer  16 C (from the side opposite to the sensor region  10 C with respect to the protective layer  16 C). Therefore, the Z fixed electrode  81 C and the Z movable electrode  82 C can be excellently protected from dust, etc. As a result, operation failures of the sensor can be reduced. 
     In addition, the base substrate  9 C is a conductive silicon substrate, so that even without applying a special treatment for giving conductivity to the Z fixed electrode  81 C and the Z movable electrode  82 C molded into predetermined shapes, the molded structures can be used as they are as electrodes. Portions except for the portions to be used as electrodes can be used as wirings (Z first detection wiring  90 C and Z second detection wiring  91 C). 
     The operation and effects in the Z-axis sensors  14 C are described in detail above, and the same operation and effects (reduction in cost due to the protective layer  16 C, simplification of the manufacturing process, shape maintenance of the protective layer  16 C, prevention of operation failures of the sensor, and stabilization of the sizes of the electrodes, etc.) as in the Z-axis sensors  14 C can also be obtained in the X-axis sensor  12 C and the Y-axis sensor  13 C. 
     The MEMS package  1 C according to the present preferred embodiment includes the X-axis sensor  12 C, the Y-axis sensor  13 C, and the Z-axis sensors  14 C, so that operation failures of the sensor can be reduced. As a result, a highly reliable MEMS package can be provided. 
     The third preferred embodiment of the present invention is described above, however the present invention can also be carried out in other embodiments. 
     For example, the MEMS package  1 C may include an angular velocity sensor instead of or in addition to the acceleration sensor  3 C. This angular velocity sensor can be manufactured by providing circuits for driving, for example, the movable electrodes  42 C,  62 C, and  82 C in the sensors  12 C to  14 C shown in  FIG. 21  to  FIG. 25 . 
     For example, a Z-axis angular velocity sensor  92 C that detects an angular velocity ω x  applied around the X axis includes, as shown in  FIG. 27 , insulating layers  94 C embedded in both sides of the portion (opposed portion  93 C) opposed to the tip end portion  95 C (described later) of each second comb tooth portion  87 C on the first base portion  83 C in the Z-axis sensor  14 C shown in  FIG. 24 . The opposed portion  93 C surrounded by the insulating layers  94 C and the triangular space of the truss structure is insulated from other portions of the first base portion  83 C. 
     Further, the Z-axis angular velocity sensor  92 C includes insulating layers  98 C embedded in portions close to the tip end portions  95 C of the second comb tooth portions  87 C. Each second comb tooth portion  87 C is partitioned into the tip end portion  95 C, the intermediate portion  96 C, and the base end portion  97 C by the insulating layers  89 C and  98 C. 
     Further, the Z-axis angular velocity sensor  92 C includes Z first drive wiring  99 C and Z second drive wiring  100 C connected to the opposed portions  93 C of the first base portion  83 C and the tip end portions  95 C of the second comb tooth portions  87 C, respectively. 
     In this Z-axis angular velocity sensor  92 C, the opposed portions  93 C of the Z fixed electrode  81 C and the tip end portions  95 C of the Z movable electrode  82 C opposed to each other at an interval therebetween constitute drive portions between which drive voltages are applied to oscillate the Z movable electrode  82 C by coulomb forces generated by changes in the drive voltages. 
     Between the opposed portions  93 C of the Z fixed electrode  81 C and the tip end portions  95 C of the Z movable electrode  82 C, drive voltages with the same polarity and drive voltages with different polarities are alternately applied via the Z first drive wiring  99 C and the Z second drive wiring  100 C. Accordingly, coulomb repulsive and attractive forces are alternately generated between the opposed portions  93 C and the tip end portions  95 C. 
     As a result, the comb-tooth-like Z movable electrode  82 C oscillates up and down like a pendulum similarly around the comb-tooth-like Z fixed electrode  81 C as a center of oscillation along the Z-axis direction with respect to the Z fixed electrode  81 C (oscillation Uz). 
     In this state, when the Z movable electrode  82 C rotates around the X axis as a central axis, a coriolis force F y  is generated in the Y-axis direction. This coriolis force F y  changes the opposing area and/or electrode-to-electrode distance d z  between the first comb tooth portions  84 C and the intermediate portions  96 C of the second comb tooth portions  87 C adjacent to each other. 
     Then, by detecting a change in capacitance between the Z movable electrode  82 C and the Z fixed electrode  81 C caused by the change in opposing area and/or electrode-to-electrode distance d z , the angular velocity ω x  around the X axis is detected. 
     The material of the protective layer  16 C is not limited to SiO 2  as long as the material is an inorganic material, and may be, for example, SiN. In this case, in order to secure the etching selectivity of the first sacrifice layer  39 C to the protective layer  16 C, the first sacrifice layer  39 C is preferably made of SiO 2 . 
     In the preferred embodiment described above, a sacrifice layer having a two-layer structure including the first sacrifice layer  39 C and the second sacrifice layer  40 C is formed, however, the sacrifice layer may have a single-layer structure, a three-layer structure, a four-layer structure, and five or more-layer structures as long as the material of the sacrifice layer has etching selectivity to the protective layer  16 C and the base substrate  9 C. 
     (4) Fourth Preferred Embodiment 
     Entire Arrangement of MEMS Package 
       FIG. 28  is a schematic perspective view of a MEMS package according to a fourth preferred embodiment of the present invention. 
     The MEMS package  1 D is used for, for example, correction of shake of a video camera or a still camera, position detection of a car navigation system, and motion detection of a robot and a gaming machine, etc. 
     The MEMS package  1 D includes a substrate  2 D, an angular velocity sensor  3 D as a MEMS sensor, external terminals  4 D, an integrated circuit  5 D (ASIC: Application Specific Integrated Circuit), and a resin package  6 D. 
     The substrate  2 D is formed to have a rectangular plate shape having a surface and a back surface. 
     The angular velocity sensor  3 D is disposed on one end portion in the longitudinal direction on the surface side of the substrate  2 D. The angular velocity sensor  3 D includes a base substrate  7 D having a square plate shape formed of a Si substrate, a sensor portion  8 D provided at the central portion of the base substrate  7 D, and electrode pads  9 D that are disposed on the lateral side of the sensor portion  8 D on the base substrate  7 D to supply a voltage to the sensor portion  8 D. 
     The sensor portion  8 D includes an X-axis sensor  10 D, a Y-axis sensor  11 D, and Z-axis sensors  12 D as sensors that respectively detect angular velocities around three axes orthogonal to each other in a three-dimensional space. These three sensors  10 D to  12 D are covered and sealed by a lid substrate  13 D that is formed of, for example, a Si substrate and bonded to the base substrate  7 D. 
     The X-axis sensor  10 D generates a coriolis force Fz in the Z-axis direction by using oscillation Ux in the X-axis direction when the MEMS package  1 D is tilted, and detects an angular velocity ωy applied around the Y axis by detecting a change in capacitance caused by the coriolis force. The Y-axis sensor  11 D generates a coriolis force Fx in the X-axis direction by using oscillation Uy in the Y-axis direction when the MEMS package  1 D is tilted, and detects an angular velocity ωz applied around the Z axis by detecting a change in capacitance caused by the coriolis force. The Z-axis sensor  12 D generates a coriolis force Fy in the Y-axis direction by using oscillation Uz in the Z-axis direction when the MEMS package  1 D is tilted, and detects an angular velocity ωx applied around the X axis by detecting a change in capacitance caused by the coriolis force. 
     A plurality (seven in  FIG. 28 ) of the electrode pads  9 D are provided at even intervals along the width direction orthogonal to the longitudinal direction of the substrate  2 D. 
     A plurality (twelve in  FIG. 28 ) of the external terminals  4 D are provided at even intervals along the width direction of the substrate  2 D on the other end portion in the longitudinal direction of the substrate  2 D (end portion on the side opposite to the angular velocity sensor  3 D). The external terminals  4 D are formed to penetrate through the substrate  2 D in the thickness direction, and are exposed as internal pads  14 D to the surface of the substrate  2 D and exposed as external pads  15 D to the back surface of the substrate  2 D. 
     The integrated circuit  5 D is disposed between the angular velocity sensor  3 D and the external terminals  4 D (internal pads  14 D) on the surface side of the substrate  2 D. The integrated circuit  5 D is formed of, for example, a Si substrate having a rectangular plate shape long in the width direction of the substrate  2 D. Inside this Si substrate, charge amplifiers that amplify electric signals output from the sensors  10 D to  12 D, filter circuits (low-pass filters: LPF, etc.) that extract specific frequency components of the electric signals, and logic circuits that carry out logic operations of filtered electric signals, etc., are formed. These circuits consist of, for example, CMOS devices. The integrated circuit  5 D includes first electrode pads  16 D and second electrode pads  17 D. 
     A plurality (seven in  FIG. 28 ) of first electrode pads  16 D are provided at even intervals along the width direction of the substrate  2 D at an end portion on the side close to the angular velocity sensor  3 D in the longitudinal direction of the substrate  2 D. The first electrode pads  16 D are connected one-to-one to the electrode pads  9 D of the angular velocity sensor  3 D by bonding wires  18 D. 
     A plurality (twelve in  FIG. 28 ) of the second electrode pads  17 D are provided at even intervals along the width direction of the substrate  2 D on an end portion on the side close to the external terminals  4 D in the longitudinal direction of the substrate  2 D. The second electrode pads  17 D are connected one-to-one to the internal pads  14 D of the external terminals  4 D by bonding wires  19 D. 
     The resin package  6 D defines the external shape of the MEMS package  1 D in cooperation with the substrate  2 D, and is formed to have a substantially rectangular parallelepiped shape. The resin package  6 D is made of, for example, a known molding resin such as epoxy resin, and covers the bonding wires  18 D and  19 D and the internal pads  14 D as well as the angular velocity sensor  3 D and the integrated circuit  5 D, and seals the angular velocity sensor  3 D and the integrated circuit  5 D in such a manner that the external pads  15 D are exposed. 
     &lt;Arrangement of Z-Axis Sensors&gt; 
     Next, an arrangement of the Z-axis sensors  12 D will be described with reference to  FIG. 29 . 
     The angular velocity sensor  3 D includes a base substrate  7 D (for example, thickness: 625 μm) as described above. 
     On the surface  20 D of the base substrate  7 D, abase insulating film  21 D (for example, thickness: 10000 Å) is formed. The base insulating film  21 D is made of SiO 2  (silicon oxide). 
     On the base insulating film  21 D, a drive electrode  22 D (for example, thickness: 5000 Å) is formed as a lower electrode. The drive electrode  22 D is made of polysilicon. 
     Further, on the base insulating film  21 D, an electrode coating film  23 D (for example, thickness: 5000 Å) that coats the drive electrode  22 D is formed. The electrode coating film  23 D is made of SiO 2 . In the electrode coating film  23 D, an opening  25 D for exposing a portion of the drive electrode  22 D as a pad  24 D is formed. 
     On the electrode coating film  23 D, a polysilicon layer  26 D (for example, thickness: 10 μm) is formed. The polysilicon layer  26 D includes a fixed electrode  27 D and a movable electrode  28 D as an upper electrode and a contact electrode  29 D. 
     The fixed electrode  27 D includes a contact portion  31 D provided to stand on the surface  30 D of the electrode coating film  23 D, and comb tooth portions  32 D formed of a plurality of electrodes aligned like comb teeth along the surface  20 D of the base substrate  7 D above the electrode coating film  23 D. 
     The contact portion  31 D of the fixed electrode  27 D includes a base portion  33 D (for example, height: 5 μm) fixed to the surface  30 D of the electrode coating film  23 D, and a joint portion  34 D that is joined integrally to the top portion of the base portion  33 D and has the same thickness (described later) as the comb tooth portions  32 D. 
     The joint portion  34 D is formed to bulge more to the outside than the side surfaces  35 D of the base portion  33 D. Accordingly, between the side surfaces  36 D of the joint portion  34 D and the side surfaces  35 D of the base portion  33 D, a step S 1  is formed. 
     The comb tooth portions  32 D of the fixed electrode  27 D are formed integrally with the joint portion  34 D of the contact portion  31 D, and one end of the comb tooth portions  32 D is supported by the joint portion  34 D so that a cavity  37 D is formed between the comb tooth portions  32 D and the surface  30 D of the electrode coating film  23 D. Specifically, the comb tooth portions  32 D are supported in a floating state by the height of the base portion  33 D of the contact portion  31 D from the surface  30 D of the electrode coating film  23 D. The thickness of the comb tooth portions  32 D (the height from the top portion of the base portion  33 D to the surface of the polysilicon layer  26 D) is, for example, approximately 15 μm. 
     The movable electrode  28 D includes a contact portion  38 D provided to stand on the surface  30 D of the electrode coating film  23 D and comb tooth portions  39 D that consist of a plurality of electrodes disposed on the respective portions between the comb tooth portions  32 D of the fixed electrode  27 D above the electrode coating film  23 D, and engage with the comb tooth portions  32 D of the fixed electrode  27 D as a whole. A distance (electrode-to-electrode distance d 1 ) of, for example, approximately 2 μm is provided between the comb tooth portions  39 D and the comb tooth portions  32 D of the fixed electrode  27 D. 
     The contact portion  38 D of the movable electrode  28 D is provided on the side opposite to the comb tooth portions  32 D of the fixed electrode  27 D with respect to the contact portion  31 D of the fixed electrode  27 D. The contact portion  38 D includes a base portion  40 D (for example, height: 5 μm) fixed to the surface  30 D of the electrode coating film  23 D, and a joint portion  41 D joined integrally to the top portion of the base portion  40 D and having the same thickness (described later) as that of the comb tooth portions  39 D. 
     The joint portion  41 D is formed to bulge more to the outside than the side surfaces  42 D of the base portion  40 D. Accordingly, a step S 2  is formed between the side surfaces  43 D of the joint portion  41 D and the side surfaces  42 D of the base portion  40 D. 
     The comb tooth portions  39 D of the movable electrode  28 D are formed integrally with the joint portion  41 D of the contact portion  38 D, and one end of the comb tooth portions  39 D is supported by the joint portion  41 D so that a cavity  37 D is formed between the comb tooth portions  39 D and the surface  30 D of the electrode coating film  23 D in the same manner as the comb tooth portions  32 D of the fixed electrode  27 D. Specifically, the comb tooth portions  39 D are supported in a floating state by the height of the base portion  40 D of the contact portion  38 D from the surface  30 D of the electrode coating film  23 D. The thickness of the comb tooth portions  39 D (the height from the top portion of the base portion  40 D to the surface of the polysilicon layer  26 D) is, for example, approximately 15 μm. 
     In the present preferred embodiment, directly below the cavity  37 D, the drive electrode  22 D is formed across the comb teeth on both ends (in  FIG. 29 , the comb tooth portion  32 D closest to the contact electrode  29 D and the comb tooth portion  39 D closest to the contact portion  31 D of the fixed electrode  27 D) so as to extend across the comb tooth portions  32 D and  39 D of the fixed electrode  27 D and the movable electrode  28 D that engage with each other like comb teeth. Accordingly, one drive electrode  22 D is opposed to all the comb tooth portions  32 D and  39 D of the fixed electrode  27 D and the movable electrode  28 D. 
     The contact electrode  29 D includes a base portion  44 D (for example, height: 5 μm) connected to the drive electrode  22 D via the opening  25 D of the electrode coating film  23 D and a joint portion  45 D joined integrally to the top portion of the base portion  44 D. 
     The joint portion  45 D is formed to bulge more to the outside than the side surfaces  46 D of the base portion  44 D. Accordingly, between the side surfaces  47 D of the joint portion  45 D and the side surfaces  46 D of the base portion  44 D, a step S 3  is formed. 
     On the polysilicon layer  26 D, a surface protective film  48 D (for example, thickness: 3000 Å) made of SiO 2  is formed. Accordingly, the surfaces of the comb tooth portions  32 D and  39 D and the contact portions  31 D and  38 D (joint portions  34 D and  41 D) of the fixed electrode  27 D and the movable electrode  28 D and the contact electrode  29 D are covered by the surface protective film  48 D. 
     On the surface protective film  48 D, at portions opposed to the contact portion  31 D of the fixed electrode  27 D, the contact portion  38 D of the movable electrode  28 D, and the contact electrode  29 D, a first detection wiring  49 D, a second detection wiring  50 D, and a drive wiring  51 D are formed, respectively. The wirings  49 D to  51 D are made of Al (aluminum), and are connected to the contact portion  31 D of the fixed electrode  27 D, the contact portion  38 D of the movable electrode  28 D, and the contact electrode  29 D, respectively, by penetrating through the surface protective film  48 D. 
     In the Z-axis sensor  12 D structured as described above, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the comb tooth portions  39 D of the movable electrode  28 D and the drive electrode  22 D. Accordingly, coulomb repulsive and attractive forces are alternately generated between the comb tooth portions  39 D of the movable electrode  28 D and the drive electrode  22 D. 
     As a result, the comb-tooth-like movable electrode  28 D oscillates up and down like a pendulum similarly around the comb-tooth-like fixed electrode  27 D as a center of oscillation along the Z-axis direction with respect to the fixed electrode  27 D (oscillation Uz). 
     In this state, when the movable electrode  28 D rotates around the X axis as a central axis, a coriolis force Fy is generated in the Y-axis direction. This coriolis force Fy changes the opposing area and/or electrode-to-electrode distance d 1  between the comb tooth portions  39 D of the movable electrode  28 D and the comb tooth portions  32 D of the fixed electrode  27 D adjacent to each other. 
     Then, by detecting a change in capacitance C between the movable electrode  28 D and the fixed electrode  27 D caused by the change in opposing area and/or electrode-to-electrode distance d 1 , the angular velocity ωx around the X axis is detected. 
     &lt;Method for Manufacturing Angular Velocity Sensor&gt; 
     Next, with reference to  FIG. 30A  to  FIG. 30L , the manufacturing process of the above-described angular velocity sensor will be described in order of steps. In this paragraph, only the manufacturing process of the Z-axis sensors is shown in the drawings, and the description of the manufacturing processes of the X-axis sensor and the Y-axis sensor are omitted, however, the manufacturing processes of the X-axis sensor and the Y-axis sensor are performed in parallel to the manufacturing process of the Z-axis sensors in the same manner as the manufacturing process of the Z-axis sensors. 
       FIG. 30A  to  FIG. 30L  are sectional views showing parts of the manufacturing process of the Z-axis sensors shown in  FIG. 29 , illustrating a section taken at the same position as in  FIG. 29 . 
     To manufacture the Z-axis sensor  12 D, as shown in  FIG. 30A , the surface  20 D of the base substrate  7 D made of conductive silicon is thermally oxidized (for example, temperature: 1000° C. to 1200° C.). Accordingly, on the surface  20 D of the base substrate  7 D, a base insulating film  21 D made of SiO 2  is formed. Next, by a CVD (Chemical Vapor Deposition) method, polysilicon is deposited on the entire surface of the base insulating film  21 D. Subsequently, by a known patterning technique, the polysilicon is selectively patterned to form the drive electrode  22 D. 
     Next, as shown in  FIG. 30B , by a CVD method, the electrode coating film  23 D made of SiO 2  having etching selectivity to polysilicon is formed on the entire surface of the base insulating film  21 D. Accordingly, the drive electrode  22 D is completely coated by the electrode coating film  23 D. 
     Here, the material having etching selectivity to polysilicon (in this paragraph, defined as material A) is, for example, a material satisfying a ratio (etching selectivity) of the etching rate of polysilicon to a certain etching medium to the etching rate of material A to the etching medium=(etching rate of material A/etching rate of polysilicon) #1. In particular, the material A preferably makes the etching selectivity closer to 0 (zero) (etching selectivity≈0), and in detail, the material A is preferably SiO 2  as in the present preferred embodiment. The electrode coating film  23 D may be made of other materials (for example, SiN, etc.) having etching selectivity to polysilicon. 
     Next, as shown in  FIG. 30C , by a CVD method, polysilicon (for example, thickness: 5000 Å) is deposited on the entire region of the surface  30 D of the electrode coating film  23 D. Subsequently, by a known patterning technique, the polysilicon is selectively patterned to form a sacrifice polysilicon layer  52 D. 
     Next, as shown in  FIG. 30D , by a CVD method, a sacrifice oxide film  53 D made of SiO 2  (for example, thickness: 5000 Å) is formed on the entire surface of the sacrifice polysilicon layer  52 D. 
     Next, as shown in  FIG. 30E , by a known patterning technique, the sacrifice oxide film  53 D is patterned, and the portions at which the base portions  33 D,  40 D, and  44 D should be formed of the sacrifice oxide film  53 D are selectively removed, and accordingly, openings  25 D,  54 D, and  55 D are formed. Accordingly, a portion of the drive electrode  22 D is exposed as a pad  24 D from the opening  25 D. 
     Next, on the sacrifice oxide film  53 D, a seed film made of polysilicon is formed. Subsequently, from this seed film, polysilicon is epitaxially grown. Accordingly, as shown in  FIG. 30F , a polysilicon layer  26 D (for example, thickness: 15 μm) is formed as an electrode polysilicon layer. 
     Next, as shown in  FIG. 30G , CMP (Chemical Mechanical Polishing) is applied until the surface of the polysilicon layer  26 D becomes flush. Accordingly, the thickness of the polysilicon layer  26 D changes from, for example, 15 μm to 10 μm. Subsequently, by a CVD method, a surface protective film  48 D made of SiO 2  is formed on the entire surface of the polysilicon layer  26 D. Subsequently, by a known patterning technique, the surface protective film  48 D is selectively removed. Accordingly, contact holes are formed in the surface protective film  48 D. Subsequently, after contact plugs filling the contact holes are formed, Al is deposited by sputtering on the surface protective film  48 D, and this Al deposition layer is patterned. Accordingly, wirings  49 D to  51 D are formed concurrently on the surface protective film  48 D. 
     Next, as shown in  FIG. 30H , by a known patterning technique, openings are formed in regions except for the regions in which the fixed electrode  27 D, the movable electrode  28 D, and the contact electrode  29 D should be formed in the surface protective film  48 D. Subsequently, by anisotropic deep RIE using the remaining surface protective film  48 D as a hard mask, specifically, by a Bosch process, the polysilicon layer  26 D is dug. In the Bosch process, a step of etching the polysilicon layer  26 D by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. Accordingly, the polysilicon layer  26 D can be etched at a high aspect ratio, however, a wavy irregularity called scallop is formed on the etched surfaces (inner peripheral surfaces of the trenches). 
     Accordingly, the polysilicon layer  26 D is molded into the shapes of the fixed electrode  27 D, the movable electrode  28 D, and the contact electrode  29 D, and between these portions (the comb tooth portions  32 D and  39 D and the contact portions  31 D and  38 D, etc.), trenches  56 D are formed. The surface of the sacrifice oxide film.  53 D is exposed to the bottom surfaces of the trenches  56 D. 
     Next, as shown in  FIG. 30I , by a CVD method, a protective thin film  57 D made of SiO 2  is formed on the entire surfaces of the fixed electrode  27 D, the movable electrode  28 D, and the contact electrode  29 D and the entire inner surfaces of the trenches  56 D (that is, the side surfaces and the bottom surfaces defining the trenches  56 D). 
     Next, as shown in  FIG. 30J , by anisotropic deep RIE, the bottom surfaces of the trenches  56 D are further dug. Accordingly, the sacrifice polysilicon layer  52 D is exposed as the bottom surfaces of the trenches  56 D. 
     Subsequent to this anisotropic deep RIE, reactive ions and etching gas (for example, SF 6  gas) are supplied into the trenches  56 D by isotropic RIE. Then, by action of the reactive ions, etc., as shown in  FIG. 30K , the sacrifice polysilicon layer  52 D is etched in the direction parallel to the surface of the base substrate  7 D while being etched in the thickness direction of the base substrate  7 D from the bottom portions of the trenches  56 D. Accordingly, the bottom portions of all trenches  56 D adjacent to each other are integrated together to form a cavity  37 D, and directly above the cavity  37 D, the fixed electrode  27 D (comb tooth portions  32 D) and the movable electrode  28 D (comb tooth portions  39 D) are in a floating state. 
     Next, as shown in  FIG. 30L , an etching gas (for example, HF (hydrofluoric acid) gas) is supplied into the trenches  56 D. By the action of this HF gas, the protective thin film  57 D and the sacrifice oxide film  53 D made of SiO 2  are removed. 
     Through the above-described steps, the Z-axis sensor  12 D shown in  FIG. 29  is obtained. 
     According to the above-described method, after the drive electrode  22 D is formed on the base substrate  7 D (the step of  FIG. 30A ), the fixed electrode  27 D and the movable electrode  28 D for angular velocity detection in the Z-axis sensor  12 D are formed by using the polysilicon layer  26 D on the base substrate  7 D. Therefore, before forming the fixed electrode  27 D and the movable electrode  28 D, the drive electrode  22 D can be easily formed directly below the fixed electrode  27 D and the movable electrode  28 D. 
     Further, in the manufacturing process of the Z-axis sensors  12 D, between the drive electrode  22 D and the polysilicon layer  26 D, the sacrifice polysilicon layer  52 D and the sacrifice oxide film  53 D are formed (the steps of  FIG. 30C  and  FIG. 30D ). These sacrifice layers  52 D and  53 D are removed after the polysilicon layer  26 D is molded into the fixed electrode  27 D and the movable electrode  28 D (the steps of  FIG. 30K  and  FIG. 30L ). Therefore, the cavity  37 D can be easily formed between the fixed electrode  27 D (comb tooth portions  32 D), the movable electrode  28 D (comb tooth portions  39 D) and the drive electrode  22 D. Accordingly, the Z-axis sensor  12 D including a capacitor in which the fixed electrode  27 D (comb tooth portions  32 D), the movable electrode  28 D (comb tooth portions  39 D) are opposed to the drive electrode  22 D vertically via the cavity  37 D can be manufactured. 
     Therefore, in the step of  FIG. 30A , by adjusting the area of the drive electrode  22 D to an appropriate size, the capacitor capacity between the movable electrode  28 D (comb tooth portions  39 D) and the drive electrode  22 D can be controlled to an optimum capacity for sensor operation. 
     In detail, the drive electrode  22 D is formed across comb teeth on both ends so as to extend across the comb tooth portions  32 D and  39 D of the fixed electrode  27 D and the movable electrode  28 D. Accordingly, the area of the drive electrode  22 D opposed to the movable electrode  28 D (comb tooth portions  39 D) can be made larger than the opposing area of the fixed electrode  27 D (comb tooth portions  32 D) to the movable electrode  28 D (comb tooth portions  39 D). Therefore, as compared with a case where drive voltages are applied between the fixed electrode  27 D and the movable electrode  28 D that engage with each other like comb teeth, the movable electrode  28 D can be oscillated with a larger amplitude. As a result, the angular velocity detection sensitivity can be improved. 
     In addition, even after the cavity  37 D is formed by removing the sacrifice polysilicon layer  52 D and the sacrifice oxide film  53 D, the drive electrode  22 D is covered by the electrode coating film  23 D. Therefore, even if the movable electrode  28 D approaches the drive electrode  22 D due to great oscillation, the movable electrode  28 D (comb tooth portions  39 D) and the drive electrode  22 D can be prevented from coming into contact with each other. As a result, the movable electrode  28 D (comb tooth portions  39 D) and the drive electrode  22 D can be prevented from being short-circuited by each other. Therefore, operation failures of the sensor can be reduced. 
     As a result, according to the MEMS package  1 D, the detection accuracy of the Z-axis sensors  12 D can be improved. 
     In the manufactured Z-axis sensor  12 D, if the protective thin film  57 D remains on the side walls of the fixed electrode  27 D and the movable electrode  28 D, as compared with the present preferred embodiment in which the protective thin film  57 D is not provided, the fixed electrode  27 D and the movable electrode  28 D are easily charged. Therefore, for example, when a voltage X (V) is applied between the fixed electrode  27 D and the movable electrode  28 D, the Z-axis sensor  12 D may erroneously recognize a potential difference between the fixed electrode  27 D and the movable electrode  28 D caused by charging as a voltage applied between the fixed electrode  27 D and the movable electrode  28 D, that is, a so-called memory effect may occur. As a result, there is a possibility that a voltage lower than the voltage X (V) is applied between the fixed electrode  27 D and the movable electrode  28 D and the designed detection performance cannot be realized. 
     Therefore, in the Z-axis sensor  12 D of the present preferred embodiment, after the cavity  37 D is formed, by removing the protective thin film  57 D (the step of  FIG. 30L ), the side walls of the fixed electrode  27 D and the movable electrode  28 D are exposed. Therefore, the occurrence of the memory effect described above can be reduced. As a result, a necessary and sufficient voltage can be applied between the fixed electrode  27 D and the movable electrode  28 D, so that the designed detection performance can be reliably realized. 
     In the Z-axis sensor  12 D, by using a portion of the polysilicon layer  26 D forming the fixed electrode  27 D and the movable electrode  28 D, the contact electrode  29 D is formed in the same layer as that of the fixed electrode  27 D and the movable electrode  28 D. Therefore, all contacts with the fixed electrode  27 D, the movable electrode  28 D, and the drive electrode  22 D can be collectively formed as the wirings  49 D to  51 D formed on the same layer (polysilicon layer  26 D). As a result, these wirings  49 D to  51 D can be formed in the same step, so that the number of manufacturing steps can be reduced. Therefore, the cost can be reduced. 
     The fourth preferred embodiment of the present invention is described above, however the present invention can also be carried out in other embodiments. 
     For example, the MEMS package  1 D may include an acceleration sensor instead of or in addition to the angular velocity sensor  3 D. The acceleration sensor can be manufactured, for example, by forming the capacitor formed between the drive electrode  22 D and the movable electrode  28 D as a capacitor for acceleration detection. 
     For example, as shown in  FIG. 31 , in a Z-axis acceleration sensor  60 D that detects acceleration applied in the Z-axis direction, in addition to the capacitor consisting of the fixed electrode  27 D (comb tooth portions  32 D) and the movable electrode  28 D (comb tooth portions  39 D), a capacitor consisting of the movable electrode  28 D (comb tooth portions  39 D) and a second fixed electrode  61 D opposed to each other via the cavity  37 D and the electrode coating film  23 D (at electrode-to-electrode distance d 2 ) along the Z-axis direction can be used for sensor operations. Accordingly, the capacitor relating to acceleration detection operations of the sensor can be increased, so that the acceleration applied to the MEMS package  1 D can be accurately detected. 
     In the above-described embodiment, in the step of  FIG. 30L , the protective thin film.  57 D and the sacrifice oxide film  53 D are removed, however, the protective thin film  57 D and the sacrifice oxide film  53 D may be left by omitting the step of  FIG. 30L  as shown in  FIG. 32 . 
     (5) Fifth Preferred Embodiment 
     Entire Arrangement of MEMS Package 
       FIG. 33  is a schematic perspective view of a MEMS package according to a fifth preferred embodiment of the present invention. 
     The MEMS package  1 E is used for, for example, correction of shake of a video camera or a still camera, position detection of a car navigation system, and motion detection of a robot and a gaming machine, etc. 
     The MEMS package  1 E includes a substrate  2 E, an angular velocity sensor  3 E as a MEMS sensor, external terminals  4 E, an integrated circuit  5 E (ASIC: Application Specific Integrated Circuit), and a resin package  6 E. 
     The substrate  2 E is formed to have a rectangular plate shape having a surface and a back surface. 
     The angular velocity sensor  3 E is disposed on one end portion in the longitudinal direction on the surface side of the substrate  2 E. The angular velocity sensor  3 E includes a base substrate  7 E formed of a Si substrate having a square plate shape, a sensor portion  8 E provided at the central portion of the base substrate  7 E, and electrode pads  9 E that are disposed on the lateral side of the sensor portion  8 E on the base substrate  7 E and supply a voltage to the sensor portion  8 E. 
     The sensor portion  8 E includes an X-axis sensor  10 E, a Y-axis sensor  11 E, and Z-axis sensors  12 E as sensors that respectively detect angular velocities around three axes orthogonal to each other in a three-dimensional space. These three sensors  10 E to  12 E are covered and sealed by a lid substrate  13 E formed of, for example, a Si substrate and bonded to the base substrate  7 E. 
     The X-axis sensor  10 E generates a coriolis force Fz in the Z-axis direction by using oscillation Ux in the X-axis direction when the MEMS package  1 E is tilted, and detects an angular velocity ωy applied around the Y axis by detecting a change in capacitance caused by the coriolis force. The Y-axis sensor  11 E generates a coriolis force Fx in the X-axis direction by using oscillation Uy in the Y-axis direction when the MEMS package  1 E is tilted, and detects an angular velocity ωz applied around the Z axis by detecting a change in capacitance caused by the coriolis force. The Z-axis sensor  12 E generates a coriolis force Fy in the Y-axis direction by using oscillation Uz in the Z-axis direction when the MEMS package  1 E is tilted, and detects an angular velocity ωx applied around the X axis by detecting a change in capacitance caused by the coriolis force. 
     A plurality (seven in  FIG. 33 ) of the electrode pads  9 E are provided at even intervals along the width direction orthogonal to the longitudinal direction of the substrate  2 E. 
     A plurality (twelve in  FIG. 33 ) of the external terminals  4 E are provided at even intervals along the width direction of the substrate  2 E on the other end portion in the longitudinal direction of the substrate  2 E (the end portion on the side opposite to the angular velocity sensor  3 E). The external terminals  4 E are formed to penetrate through the substrate  2 E in the thickness direction, and are exposed as internal pads  14 E to the surface of the substrate  2 E and exposed as external pads  15 E to the back surface of the substrate  2 E. 
     The integrated circuit  5 E is disposed between the angular velocity sensor  3 E and the external terminals  4 E (internal pads  14 E) on the surface side of the substrate  2 E. The integrated circuit  5 E is formed of, for example, a Si substrate having a rectangular plate shape long in the width direction of the substrate  2 E. Inside the Si substrate, charge amplifiers that amplify electric signals output from the sensors  10 E to  12 E, filter circuits (low-pass filters: LPF, etc.) that extract specific frequency components of the electric signals, and logic circuits that carry out logic operations of filtered electric signals, etc., are formed. These circuits consist of, for example, CMOS devices. The integrated circuit  5 E includes first electrode pads  16 E and second electrode pads  17 E. 
     A plurality (seven in  FIG. 33 ) of the first electrode pads  16 E are provided at even intervals along the width direction of the substrate  2 E on the end portion on the side close to the angular velocity sensor  3 E in the longitudinal direction of the substrate  2 E. The first electrode pads  16 E are connected one-to-one to the electrode pads  9 E of the angular velocity sensor  3 E by bonding wires  18 E. 
     A plurality (twelve in  FIG. 33 ) of the second electrode pads  17 E are provided at even intervals along the width direction of the substrate  2 E on the end portion on the side close to the external terminals  4 E in the longitudinal direction of the substrate  2 E. The second electrode pads  17 E are connected one-to-one to the internal pads  14 E of the external terminals  4 E by bonding wires  19 E. 
     The resin package  6 E defines the external shape of the MEMS package  1 E in cooperation with the substrate  2 E, and is formed to have a substantially rectangular parallelepiped shape. The resin package  6 E is made of, for example, a known molding resin such as epoxy resin, and covers the bonding wires  18 E and  19 E and the internal pads  14 E together with the angular velocity sensor  3 E and the integrated circuit  5 E, and seals the angular velocity sensor  3 E and the integrated circuit  5 E in such a manner that the external pads  15 E are exposed. 
     &lt;Arrangement of X-Axis Sensor and Y-Axis Sensor&gt; 
     Next, with reference to  FIG. 34  to  FIG. 36 , an arrangement of the X-axis sensor and the Y-axis sensor will be described. 
       FIG. 34  is a schematic plan view of the angular velocity sensor shown in  FIG. 1 .  FIG. 35  is a plan view of a principal portion of the X-axis sensor shown in  FIG. 2 .  FIG. 36  is a sectional view of the principal portion of the X-axis sensor shown in  FIG. 2 , illustrating a section taken along the cutting plane H-H in  FIG. 35 . 
     The angular velocity sensor  3 E includes a base substrate  7 E formed of a Si substrate as described above. On the surface layer portion of the base substrate  7 E (the portion opposed to the lid substrate  13 E of the base substrate  7 E), a recess  20 E having a rectangular shape in a plan view is formed. 
     On the base substrate  7 E, a base insulating layer  21 E (for example, thickness: 2 μm to 10 μm) as a base film and a polysilicon layer  22 E (for example, thickness: 5 μm to 20 μm) are laminated in order so as to cover the recess  20 E. Accordingly, inside the lamination structure consisting of the base substrate  7 E, the base insulating layer  21 E, and the polysilicon layer  22 E of the angular velocity sensor  3 E, a cavity  23 E partitioned by the base insulating layer  21 E and the base substrate  7 E is formed. 
     The X-axis sensor  10 E, the Y-axis sensor  11 E, and the Z-axis sensors  12 E have a lamination structure including the base insulating layer  21 E and the polysilicon layer  22 E, and are disposed directly above the cavity  23 E. Specifically, the X-axis sensor  10 E, the Y-axis sensor  11 E, and the Z-axis sensors  12 E are provided in a floating state with respect to the bottom wall  24 E of the base substrate  7 E forming the bottom surface that partitions the cavity  23 E from the back surface side. 
     The X-axis sensor  10 E and the Y-axis sensor  11 E are disposed adjacent to each other at an interval. The Z-axis sensors  12 E are disposed to surround the X-axis sensor  10 E and the Y-axis sensor  11 E, respectively. 
     In the present preferred embodiment, the Y-axis sensor  11 E has an arrangement substantially similar to an arrangement obtained by rotating 90 degrees the X-axis sensor  10 E in a plan view. Therefore, hereinafter, instead of a detailed description of the arrangement of the Y-axis sensor  11 E, in the description of the portions of the X-axis sensor  10 E, portions of the Y-axis sensor corresponding to the portions of the X-axis sensor are also described with parentheses. 
     Between the X-axis sensor  10 E and the Z-axis sensor  12 E and between the Y-axis sensor  11 E and the Z-axis sensor  12 E, support portions  25 E for supporting these in a floating state are formed. 
     The support portions  25 E have a lamination structure of the base substrate  7 E, the base insulating layer  21 E, and the polysilicon layer  22 E, and integrally include straight portions  26 E and annular portions  27 E. 
     The straight portions  26 E of the support portions  25 E extend across the Z-axis sensors  12 E from one side walls  28 E of the lamination structure that form the side surfaces partitioning the cavity  23 E from the lateral sides toward the X-axis sensor  10 E and the Y-axis sensor  11 E. The annular portions  27 E of the support portions  25 E surround the X-axis sensor  10 E and the Y-axis sensor  11 E. 
     The X-axis sensor  10 E and the Y-axis sensor  11 E are disposed inside the annular portions  27 E, and both ends of the sensors are supported at two points opposing each other on the inner walls of the annular portions  27 E. Both ends of the Z-axis sensors  12 E are supported on both side walls of the straight portions  26 E. 
     The X-axis sensor  10 E (Y-axis sensor  11 E) has an X fixed electrode  31 E (Y fixed electrode  51 E) and an X movable electrode  32 E (Y movable electrode  52 E) formed to have the same thickness. 
     The X fixed electrode  31 E (Y fixed electrode  51 E) is fixed to the support portion  25 E provided inside the cavity  23 E. 
     The X fixed electrode  31 E (Y fixed electrode  51 E) includes a first base portion  33 E (first base portion  53 E of the Y fixed electrode  51 E) having a quadrilateral annular shape in a plan view and fixed to the support portion  25 E, and a plurality of pairs of first comb tooth portions  34 E (first comb tooth portions  54 E of the Y fixed electrode  51 E) aligned like comb teeth at even intervals along the inner wall of the first base portion  33 E. 
     The first base portion  33 E of the X fixed electrode  31 E has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     As the first comb tooth portions  34 E of the X fixed electrode  31 E, two electrode portions that have base end portions connected to the first base portion  33 E and tip end portions thereof straight in a plan view and opposed to each other are paired, and a plurality of the pairs are provided at even intervals. Each first comb tooth portion  34 E has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other and a plurality of traverse frames laid across the main frames. 
     The X movable electrode  32 E (Y movable electrode  52 E) is held to be capable of oscillating with respect to the X fixed electrode  31 E. 
     The X movable electrode  32 E (Y movable electrode  52 E) includes a second base portion  35 E (second base portion  55 E of the Y movable electrode  52 E) and second comb tooth portions  36 E (second comb tooth portions  56 E of the Y movable electrode  52 E). 
     The second base portion  35 E of the X movable electrode  32 E is formed of a plurality (six in the present preferred embodiment) of straight frames extending parallel to each other along a direction across the first comb tooth portions  34 E of the X fixed electrode  31 E. Both ends of the second base portion  35 E are connected to beam portions  37 E (beam portions  57 E of the Y-axis sensor  11 E) capable of expanding and contracting along a direction across the first comb tooth portions  34 E. 
     Two beam portions  37 E are provided on each of the ends of the second base portion  35 E of the X movable electrode  32 E. 
     The second comb tooth portions  36 E of the X movable electrode  32 E extend to both sides from the second base portion  35 E toward the portions between the first comb tooth portions  34 E adjacent to each other of the X fixed electrode  31 E, and are aligned like comb teeth to engage with the first comb tooth portions  34 E of the X fixed electrode  31 E without contact. Each second comb tooth portion  36 E has a framed structure having a ladder-like shape in a plan view including straight main frames extending parallel to each other across the frames of the second base portion  35 E and a plurality of traverse frames laid across the main frames. 
     In the X movable electrode  32 E, on lines halving the second comb tooth portions  36 E along a direction orthogonal to the oscillation direction Ux, insulating layers  38 E across the traverse frames are embedded from the surface of the polysilicon layer  22 E to the base insulating layer  21 E. 
     The insulating layers  38 E are made of SiO 2  (silicon oxide), and are formed integrally with the base insulating layer  21 E. The second comb tooth portions  36 E are insulated and separated into two of one side and the other side along the oscillation direction Ux by the insulating layers  38 E. Accordingly, the separated second comb tooth portions  36 E of the X movable electrode  32 E function as independent electrodes in the X movable electrode  32 E. 
     On the polysilicon layer  22 E, a first insulating film  42 E and a second insulating film  43 E made of SiO 2  are laminated in order. On the second insulating film  43 E, an X first drive/detection wiring  39 E (Y first drive/detection wiring  59 E) and an X second drive/detection wiring  40 E (Y second drive/detection wiring  60 E) are formed. 
     The X first drive/detection wiring  39 E supplies a drive voltage to one side (in the present preferred embodiment, the left side on the paper surface of  FIG. 35 ) of each second comb tooth portion  36 E insulated and separated into two, and detects a change in voltage accompanying a change in capacitance from the second comb tooth portion  36 E. 
     The X second drive/detection wiring  40 E supplies a drive voltage to the other side (in the present preferred embodiment, the right side on the paper surface of  FIG. 35 ) of each second comb tooth portion  36 E insulated and separated into two, and detects a change in voltage accompanying a change in capacitance from the second comb tooth portion  36 E. 
     The first drive/detection wiring  39 E and the X second drive/detection wiring  40 E are made of Al (aluminum) in the present preferred embodiment. The X first drive/detection wiring  39 E and the X second drive/detection wiring  40 E are electrically connected to the second comb tooth portions  36 E by penetrating through the first insulating film  42 E and the second insulating film  43 E. 
     The X first drive/detection wiring  39 E and the X second drive/detection wiring  40 E are led onto the support portion  25 E via the beam portions  37 E of the X movable electrode  32 E and the first base portion  33 E of the X fixed electrode  31 E, and partially exposed as electrode pads  9 E. 
     The X first drive/detection wiring  39 E and the X second drive/detection wiring  40 E use the beam portions  37 E themselves formed of portions of the conductive polysilicon layer  22 E as current paths in sections passing through the beam portions  37 E of the X movable electrode  32 E, respectively. Al wirings may not be provided on the beam portion  37 E, so that the expandability of the beam portions  37 E can be maintained. 
     To the support portion  25 E, an X third drive/detection wiring  41 E that detects a change in voltage accompanying a change in capacitance from the first comb tooth portions  34 E of the X fixed electrode  31 E is led. The X third drive/detection wiring  41 E is also partially exposed as an electrode pad  9 E (not shown) in the same manner as other wirings  39 E and  40 E. 
     The upper surfaces and side surfaces of the X fixed electrode  31 E and the X movable electrode  32 E are coated by the protective thin film  44 E made of SiO 2  so that the first insulating film  42 E and the second insulating film  43 E are covered. 
     On the polysilicon layer  22 E, at portions except for the cavity  23 E, a third insulating film  45 E, a fourth insulating film  46 E, a fifth insulating film  47 E, and a surface protective film  48 E are laminated in order on the second insulating film  43 E. 
     In the X-axis sensor  10 E structured as described above, via the X first to X third drive/detection wirings  39 E to  41 E, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the X fixed electrode  31 E and the X movable electrode  32 E. Accordingly, coulomb repulsive and attractive forces are alternately generated between the first comb tooth portions  34 E of the X fixed electrode  31 E and the second comb tooth portions  36 E of the X movable electrode  32 E. 
     As a result, the comb-tooth-like X movable electrode  32 E oscillates similarly to the left and right along the X axis direction with respect to the comb-tooth-like X fixed electrode  31 E (oscillation Ux). 
     In this state, when the X movable electrode  32 E rotates around the Y axis as a central axis, a coriolis force Fz is generated in the Z axis direction. This coriolis force Fz changes the opposing area and/or distance between the first comb tooth portions  34 E of the X fixed electrode  31 E and the second comb tooth portions  36 E of the X movable electrode  32 E adjacent to each other. 
     Then, by detecting a change in capacitance between the X movable electrode  32 E and the X fixed electrode  31 E caused by the change in opposing area and/or distance, the angular velocity ωy around the Y axis is detected. 
     In the present preferred embodiment, the angular velocity ωy around the Y axis is obtained by calculating a difference between detection values of the one side and the other side, respectively, electrode portions insulated and separated from each other of the X movable electrode  32 E. 
     In the Y-axis sensor  11 E, via the Y first to Y third drive/detection wirings  59 E to  61 E, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the Y fixed electrode  51 E and the Y movable electrode  52 E. Accordingly, coulomb repulsive and attractive forces are alternately generated between the first comb tooth portions  54 E of the Y fixed electrode  51 E and the second comb tooth portions  56 E of the Y movable electrode  52 E. 
     As a result, the comb-tooth-like Y movable electrode  52 E oscillates similarly to the left and right along the Y-axis direction with respect to the comb-tooth-like Y fixed electrode  51 E (oscillation Uy). 
     In this state, when the Y movable electrode  52 E rotates around the Y axis as a central axis, a coriolis force Fx is generated in the X-axis direction. This coriolis force Fx changes the opposing area and/or distance between the first comb tooth portions  54 E of the Y fixed electrode  51 E and the second comb tooth portions  56 E of the Y movable electrode  52 E adjacent to each other. 
     Then, by detecting a change in capacitance between the Y movable electrode  52 E and the Y fixed electrode  51 E caused by the change in opposing area and/or distance, the angular velocity ωz around the Z axis is detected. 
     &lt;Arrangement of Z-Axis Sensor&gt; 
     Next, an arrangement of the Z-axis sensors will be described with reference to  FIG. 34 ,  FIG. 37 , and  FIG. 38 . 
       FIG. 37  is a plan view of a principal portion of the Z-axis sensor of  FIG. 34 .  FIG. 38  is a sectional view of the principal portion of the Z-axis sensor shown in  FIG. 34 , illustrating a section taken along the cutting plane I-I in  FIG. 37 . 
     The Z-axis sensors  12 E are disposed to surround the X-axis sensor  10 E and the Y-axis sensor  11 E, respectively, directly above the cavity  23 E as described above. 
     Each Z-axis sensor  12 E includes a Z fixed electrode  71 E and a Z movable electrode  72 E formed to have the same thickness and the same width. In  FIG. 37  and  FIG. 38 , the thickness and width of the Z fixed electrode  71 E are thickness T 1  and width W 1 , respectively, and the thickness and width of the Z movable electrode  72 E are thickness T 2  and width W 2 , respectively. 
     The Z fixed electrode  71 E is fixed to the support portion  25 E (straight portion  26 E) provided inside the cavity  23 E. 
     The Z movable electrode  72 E is held to be capable of oscillating with respect to the Z fixed electrode  71 E. 
     In the present preferred embodiment, in one Z-axis sensor  12 E of the two Z-axis sensors  12 E, the Z movable electrode  72 E is disposed to surround the annular portion  27 E, and the Z fixed electrode  71 E is disposed to surround this Z movable electrode  72 E. 
     In the other Z-axis sensor  12 E, the Z fixed electrode  71 E is disposed to surround the annular portion  27 E, and the Z movable electrode  72 E is disposed to surround this Z fixed electrode  71 E. 
     In each Z-axis sensor  12 E, the Z fixed electrode  71 E includes a first base portion  73 E and a plurality of first comb tooth portions  74 E. 
     The first base portion  73 E of the Z fixed electrode  71 E is formed to have a quadrilateral annular shape in a plan view fixed to the support portion  25 E. The first base portion  73 E has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     In the first base portion  73 E, on both sides of the portion (opposed portion  75 E) opposed to the tip end portion  82 E (described later) of each second comb tooth portion  79 E, insulating layers  76 E across the main frame of the truss structure in the width direction are embedded from the surface of the polysilicon layer  22 E to the cavity  23 E. 
     The insulating layers  76 E are made of SiO 2 , and are formed integrally with the base insulating layer  21 E. Accordingly, the opposed portion  75 E surrounded by the insulating layers  76 E and the triangular space of the truss structure is insulated from other portions of the first base portion  73 E of the Z fixed electrode  71 E. 
     The first comb tooth portions  74 E of the Z fixed electrode  71 E are aligned like comb teeth at even intervals along the inner wall of the first base portion  73 E on the portion on the side opposite to the straight portion  26 E with respect to the X-axis sensor  10 E (Y-axis sensor  11 E) on the first base portion  73 E. 
     The first comb tooth portions  74 E have base end portions connected to the first base portion  73 E of the Z fixed electrode  71 E and tip end portions extending toward the Z movable electrode  72 E. In portions close to the base end portions of the first comb tooth portions  74 E, insulating layers  77 E across the first comb tooth portions  74 E in the width direction are embedded from the surface of the polysilicon layer  22 E to the cavity  23 E. 
     The insulating layers  77 E are made of SiO 2 , and formed integrally with the base insulating layer  21 E. Each first comb tooth portion  74 E is insulated from other portions of the Z fixed electrode  71 E by the insulating layer  77 E. 
     In each Z-axis sensor  12 E, the Z movable electrode  72 E includes a second base portion  78 E and second comb tooth portions  79 E. 
     The second base portion  78 E of the Z movable electrode  72 E is formed to have a quadrilateral annular shape in a plan view. The second base portion  78 E has a truss-shaped framed structure including straight main frames extending parallel to each other and reinforcing frames combined with the main frames so that a triangular space is repeatedly formed along the main frames. 
     The second base portion  78 E of the framed structure has sections in which the reinforcing frames are omitted at portions on the side opposite to the disposition of the second comb tooth portions  79 E. The main frames in these omitted sections function as beam portions  80 E for enabling the Z movable electrode  72 E to move up and down. 
     The second comb tooth portions  79 E of the Z movable electrode  72 E extend from the second base portion  78 E toward the portions between the first comb tooth portions  74 E adjacent to each other of the Z fixed electrode  71 E, and are aligned like comb teeth that engage with the first comb tooth portions  74 E without contact. 
     The second comb tooth portions  79 E have base end portions  81 E connected to the second base portion  78 E of the Z movable electrode  72 E and tip end portions  82 E extending toward the portions between the first comb tooth portions  74 E of the Z fixed electrode  71 E. 
     In portions close to the tip end portions  82 E of the second comb tooth portions  79 E, insulating layers  84 E across the second comb tooth portions  79 E in the width direction are embedded from the surface of the polysilicon layer  22 E to the cavity  23 E. In portions close to the base end portions  81 E of the second comb tooth portions  79 E, insulating layers  85 E across the second comb tooth portions  79 E in the width direction are embedded from the surface of the polysilicon layer  22 E to the cavity  23 E. 
     The insulating layers  84 E and  85 E are made of SiO 2 , and are formed integrally with the base insulating layer  21 E. By the insulating layers  84 E and  85 E, each second comb tooth portion  79 E has three portions (the tip end portion  82 E, the base end portion  81 E, and an intermediate portion  83 E between the tip end portion  82 E and the base end portion  81 E) insulated from other portions. 
     On the polysilicon layer  22 E, as described above, a first insulating film  42 E and a second insulating film  43 E made of SiO 2  are laminated in order. On the second insulating film  43 E, a Z first detection wiring  86 E, a Z first drive wiring  87 E, a Z second detection wiring  88 E, and a Z second drive wiring  89 E are formed. 
     The Z first detection wiring  86 E and the Z second detection wiring  88 E are connected, respectively, to the first comb tooth portions  74 E of the Z fixed electrode  71 E and the intermediate portions  83 E of the Z movable electrode  72 E adjacent to each other. Specifically, in the Z-axis sensor  12 E, the first comb tooth portions  74 E of the Z fixed electrode  71 E and the intermediate portions  83 E of the Z movable electrode  72 E are opposed to each other at an electrode-to-electrode distance d, and constitute electrodes of a capacitor (detector) when a fixed voltage is applied therebetween and the capacitance changes according to a change in the electrode-to-electrode distance d and/or opposing area. 
     In detail, the Z first detection wiring  86 E is formed along the first base portion  73 E, and includes Al wirings branched toward the tip end portions of the first comb tooth portions  74 E across the insulating layers  77 E of the first comb tooth portions  74 E. 
     The branched Al wirings are electrically connected to the tip end sides relative to the insulating layers  77 E of the first comb tooth portions  74 E by penetrating through the first insulating film  42 E and the second insulating film  43 E. 
     As shown in  FIG. 34 , the Z first detection wiring  86 E is led onto the support portion  25 E via the first base portion  73 E, and partially exposed as an electrode pad  9 E. 
     The Z second detection wiring  88 E detects a change in voltage accompanying a change in capacitance from the second comb tooth portions  79 E of the Z movable electrode  72 E. The Z second detection wiring  88 E is formed along the second base portion  78 E, and includes Al wirings branched toward the intermediate portions  83 E across the insulating layers  85 E close to the base end portions  81 E of the second comb tooth portions  79 E. 
     The branched Al wirings are electrically connected to the intermediate portions  83 E of the second comb tooth portions  79 E by penetrating through the first insulating film  42 E and the second insulating film  43 E. 
     As shown in  FIG. 34 , the Z second detection wiring  88 E is led onto the support portion  25 E via the second base portion  78 E of the Z movable electrode  72 E, and partially exposed as an electrode pad  9 E. 
     The Z first drive wiring  87 E and the Z second drive wiring  89 E are connected, respectively, to the opposed portions  75 E and the tip end portions  82 E that face each other in the direction orthogonal to the opposing direction of the electrodes constituting a capacitor. Specifically, in the Z-axis sensor  12 E, the opposed portions  75 E of the Z fixed electrode  71 E and the tip end portions  82 E of the Z movable electrode  72 E opposed to each other at an interval constitute drive portions between which drive voltages are applied to oscillate the Z movable electrode  72 E by coulomb forces generated by changes in the drive voltages. 
     In detail, the Z first drive wiring  87 E supplies a drive voltage to the opposed portions  75 E of the Z fixed electrode  71 E. The Z first drive wiring  87 E includes Al wirings across both sides of the insulating layers  76 E by using the surface of the second insulating film  43 E. The Z first drive wiring  87 E is electrically connected to the opposed portions  75 E and portions except for the opposed portions  75 E of the first base portion  73 E by penetrating through the first insulating film  42 E and the second insulating film  43 E. The portion except for the Al wirings of the Z first drive wiring  87 E is formed by using the first base portion  73 E formed of the conductive polysilicon layer  22 E. 
     As shown in  FIG. 34 , the Z first drive wiring  87 E is led onto the support portion  25 E and partially exposed as an electrode pad  9 E. 
     The Z second drive wiring  89 E supplies a drive voltage to the tip end portions  82 E of the Z movable electrode  72 E. The Z second drive wiring  89 E includes Al wirings laid across the tip end portions  82 E and the base end portions  81 E of the second comb tooth portions  79 E by using the surface of the second insulating film  43 E. The Z second drive wiring  89 E is electrically connected to the tip end portions  82 E and the base end portions  81 E by penetrating through the first insulating film  42 E and the second insulating film  43 E. The portion except for the Al wirings of the Z second drive wiring  89 E is formed by using the second base portion  78 E formed of the conductive polysilicon layer  22 E. 
     As shown in  FIG. 34 , the Z second drive wiring  89 E is led onto the support portion  25 E, and partially exposed as an electrode pad  9 E. 
     The upper surfaces and the side surfaces of the Z fixed electrode  71 E and the Z movable electrode  72 E are coated by a protective thin film  44 E made of SiO 2  so that the first insulating film  42 E and the second insulating film  43 E are covered. 
     In the Z-axis sensor  12 E structured as described above, drive voltages with the same polarity and drive voltages with different polarities are alternately applied between the opposed portions  75 E of the Z fixed electrode  71 E and the tip end portions  82 E of the Z movable electrode  72 E via the Z first drive wiring  87 E and the Z second drive wiring  89 E. Accordingly, coulomb repulsive and attractive forces are alternately generated between the opposed portions  75 E and the tip end portions  82 E. 
     As a result, the comb-tooth-like Z movable electrode  72 E oscillates up and down like a pendulum similarly around the comb-tooth-like Z fixed electrode  71 E as a center of oscillation along the Z-axis direction with respect to the Z fixed electrode  71 E (oscillation Uz). 
     In this state, when the Z movable electrode  72 E rotates around the X axis as a central axis, a coriolis force Fy is generated in the Y-axis direction. This coriolis force Fy changes the opposing area and/or electrode-to-electrode distance d between the first comb tooth portions  74 E and the intermediate portions  83 E of the second comb tooth portions  79 E adjacent to each other. 
     Then, by detecting a change in capacitance C between the Z movable electrode  72 E and the Z fixed electrode  71 E caused by the change in opposing area and/or electrode-to-electrode distance d, the angular velocity ωx around the X axis is detected. 
     In the present preferred embodiment, the angular velocity ωx around the X axis is obtained by calculating a difference between a detection value of the Z-axis sensor  12 E surrounding the X-axis sensor  10 E and a detection value of the Z-axis sensor  12 E surrounding the Y-axis sensor  11 E. 
     For example, as shown in  FIG. 34 , the difference is obtained by making the position relationship between the fixed electrode and the movable electrode of the Z-axis sensor  12 E surrounding the X-axis sensor  10 E opposite to the position relationship between the fixed electrode and the movable electrode of the Z-axis sensor  12 E surrounding the Y-axis sensor  11 E. Accordingly, the manner of oscillation of the Z movable electrode  72 E differs between the pair of Z-axis sensors  12 E, so that the difference occurs. 
     &lt;Method for Manufacturing Angular Velocity Sensor&gt; 
     Next, with reference to  FIG. 39A  to  FIG. 39K , the manufacturing process of the above-described angular velocity sensor will be described in order of steps. In this paragraph, only the manufacturing process of the Z-axis sensors is shown in the drawings, and the description of the manufacturing processes of the X-axis sensor and the Y-axis sensor are omitted, however, the manufacturing processes of the X-axis sensor and the Y-axis sensor are performed in the same manner as in the manufacturing process of the Z-axis sensors in parallel to the manufacturing process of the Z-axis sensors. 
       FIG. 39A  to  FIG. 39K  are schematic sectional views showing parts of the manufacturing process of the Z-axis sensors shown in  FIG. 34  in order of steps, illustrating a section taken along the cutting plane at the same position as in  FIG. 38 . 
     To manufacture the Z-axis sensors  12 E, the surface of the base substrate  7 E made of conductive silicon is thermally oxidized (for example, temperature: 1000° C. to 1200° C.) Accordingly, a mask (not shown) made of SiO 2  is formed on the surface of the base substrate  7 E. Next, by a known patterning technique, the mask is patterned, and openings are formed at portions covering regions other than the regions in which the insulating layers  76 E,  77 E,  84 E and  85 E should be formed. 
     Next, by anisotropic deep RIE (Reactive Ion Etching) using this mask as a hard mask, specifically, by a Bosch process, trenches (for example, depth: approximately 10 μm) are selectively formed in the base substrate  7 E. In the Bosch process, a step of etching the base substrate  7 E by using SF 6  (sulfur hexafluoride) and a step of forming a protective film on the etched surfaces by using C 4 F 8  (perfluorocyclobutane) are alternately repeated. Accordingly, the base substrate  7 E can be etched at a high aspect ratio, however, a wavy irregularity called scallop is formed on the etched surfaces (inner peripheral surfaces of the trenches). 
     Accordingly, as shown in  FIG. 39A , the left columnar portions where the trenches were not formed of the base substrate  7 E are formed as columnar portions  29 E having the same shapes as the insulating layers  76 E,  77 E,  84 E, and  85 E, and a plate-shaped base portion  30 E that integrally supports the bottom portions of the columnar portions  29 E is formed concurrently. 
     Next, as shown in  FIG. 39B , the columnar portions  29 E and the base portion  30 E of the base substrate  7 E are thermally oxidized (for example, temperature: 1000° C. to 1200° C.) Accordingly, the entire columnar portions  29 E and the surface layer portion of the base portion  30 E are altered into insulating films made of SiO 2 . Among the altered insulating films, the columnar portions  29 E become the insulating layers  76 E,  77 E,  84 E, and  85 E and the surface layer portion of the base portion  30 E becomes the base insulating layer  21 E, respectively. 
     Next, on the surfaces of the insulating layers  76 E,  77 E,  84 E, and  85 E and the base insulating layer  21 E, a seed film made of polysilicon is formed. Subsequently, from this seed film, polysilicon is epitaxially grown. This epitaxial growth is continued until the height of the grown polysilicon layer  22 E becomes higher than the top portions (only the top portion  49 E of the insulating layer  85 E is shown in  FIG. 39C ) of the columnar portions  29 E altered into the insulating layers  76 E,  77 E,  84 E, and  85 E as shown in  FIG. 39C . 
     Next, as shown in  FIG. 39D , by applying CMP (Chemical Mechanical Polishing) to the surface of the polysilicon layer  22 E, the surface of the polysilicon layer  22 E is made flush with the top portions  49 E of the columnar portions  29 E (insulating layer  85 E). The top portions  49 E of the columnar portions  29 E are exposed to the surface of the polysilicon layer  22 E. 
     Next, as shown in  FIG. 39E , by a CVD method, the first insulating film  42 E made of SiO 2  is laminated on the polysilicon layer  22 E. 
     Next, as shown in  FIG. 39F , the second insulating film  43 E is laminated on the first insulating film  42 E. Subsequently, the second insulating film  43 E and the first insulating film  42 E are successively etched. Accordingly, contact holes are formed in the second insulating film  43 E and the first insulating film  42 E. Subsequently, after contact plugs filling the contact holes are formed, Al is deposited (for example, 7000 Å) by sputtering on the second insulating film  43 E, and the Al deposition layer is patterned. Accordingly, wirings  86 E to  89 E are formed on the second insulating film  43 E. 
     Next, as shown in  FIG. 39G , by a CVD method, the third insulating film  45 E, the fourth insulating film  46 E, the fifth insulating film  47 E, and the surface protective film  48 E are laminated in order on the second insulating film  43 E. Next, the third to fifth insulating films  45 E to  47 E and the surface protective film  48 E on the region in which the recess  20 E should be formed of the base substrate  7 E are removed by etching. 
     Next, as shown in  FIG. 39H , a resist having openings in regions except for the regions in which the Z fixed electrode  71 E and the Z movable electrode  72 E should be formed is formed on the second insulating film  43 E. Subsequently, by anisotropic deep RIE using the resist as a mask, specifically, by a Bosch process, the polysilicon layer  22 E and the base insulating layer  21 E are dug in order. Accordingly, the lamination structure of the base insulating layer  21 E and the polysilicon layer  22 E is molded into the shapes of the Z fixed electrode  71 E as a first electrode or a second electrode and the Z movable electrode  72 E as a first electrode or a second electrode, and between these, trenches  50 E are formed. To the bottom surfaces of the trenches  50 E, the surface of the base substrate  7 E is exposed. 
     Next, as shown in  FIG. 39I , by thermal oxidization or by a PECVD method, on the entire surfaces of the Z fixed electrode  71 E and the Z movable electrode  72 E and the entire inner surfaces of the trenches  50 E (that is, the side surfaces and bottom surfaces defining the trenches  50 E), a protective thin film  44 E made of SiO 2  is formed. 
     Next, as shown in  FIG. 39J , by etching back, the portions on the bottom surfaces of the trenches  50 E of the protective thin film  44 E are removed. Accordingly, the bottom surfaces of the trenches  50 E are exposed. 
     Next, as shown in  FIG. 39K , by anisotropic deep RIE using the surface protective film  48 E as a mask, the bottom surfaces of the trenches  50 E (that is, the surface of the base substrate  7 E) are further dug. Accordingly, in the bottom portions of the trenches  50 E (the surface layer portion of the base substrate  7 E), exposure spaces  58 E to which the crystal face of the base substrate  7 E is exposed are formed. 
     Subsequent to this anisotropic deep RIE, by isotropic RIE, reactive ions and etching gas as etching media are supplied into the exposure spaces  58 E of the trenches  50 E. Then, by action of the reactive ions, etc., the base substrate  7 E is etched in a direction parallel to the surface of the base substrate  7 E while being etched in the thickness direction of the base substrate  7 E from the exposure spaces  58 E. Accordingly, all exposure spaces  58 E adjacent to each other are integrated to form a recess  20 E (cavity  23 E) on the surface layer portion of the base substrate  7 E, and directly above the recess  20 E, the Z fixed electrode  71 E and the Z movable electrode  72 E is in a floating state. 
     Through the above-described steps, the Z-axis sensors  12 E shown in  FIG. 34  are obtained. 
     According to the method described above, the lowest portions of the Z fixed electrode  71 E and the Z movable electrode  72 E are formed of the base insulating layer  21 E made of SiO 2  having etching selectivity to Si. Further, the side surfaces of the Z fixed electrode  71 E and the Z movable electrode  72 E are also covered by the protective thin film  44 E made of SiO 2 . 
     Therefore, in the step of  FIG. 39K , when reactive ions and etching gas are supplied into the exposure spaces  58 E and the base substrate  7 E is isotropically etched, even if the etching gas, etc., come into contact with the Z fixed electrode  71 E and the Z movable electrode  72 E, the Z fixed electrode  71 E and the Z movable electrode  72 E can be prevented from being eroded by the etching gas. As a result, the variation in size (the thicknesses T 1  and T 2  and the width W 1  and W 2 ) of the Z fixed electrode  71 E and the Z movable electrode  72 E can be reduced. 
     Therefore, in the Z-axis sensor  12 E, the opposing area between the first comb tooth portions  74 E and the intermediate portions  83 E of the second comb tooth portions  79 E according to the thicknesses T 1  and T 2  of the Z fixed electrode  71 E and the Z movable electrode  72 E, and the electrode-to-electrode distance d according to the widths W 1  and W 2  of the Z fixed electrode  71 E and the Z movable electrode  72 E can be maintained constantly. Therefore, a change in capacitance between the Z movable electrode  72 E and the Z fixed electrode  71 E caused by a change in the opposing area and/or electrode-to-electrode distance d can be accurately detected. 
     The variations in the widths W 1  and W 2  of the Z fixed electrode  71 E and the Z movable electrode  72 E are small, so that the magnitudes of coulomb repulsive and attractive forces to be generated at the respective portions between the opposed portions  75 E and the tip end portions  82 E can be made substantially equal to each other among the respective portions. As a result, the Z movable electrode  72 E can be driven as designed. 
     In the invention described in Patent Document 1, the plurality of portions that should be electrically insulated in the Si substrate are isolated by isolation joints (isolation joints 160, 360 . . . ). These isolation joints are formed by forming trenches in a Si substrate and thermally oxidizing the inner walls (side walls and bottom walls) of the trenches as shown in FIG. 6a of Patent Document 1. When the inner walls of the trenches are thermally oxidized, SiO 2  grows from the side walls and the bottom walls toward the insides of the trenches, and SiO 2  grown from the walls are eventually integrated. By this integration, isolation joints (612 in FIG. 6a) embedded in the trenches are obtained. However, the isolation joints thus obtained are films formed by growing a plurality of SiO 2  inside trenches that were originally void and integrating these, so that the strength of the films is not so high, and this formation takes time (for example, the etching rate is approximately 2 μm/h). 
     Therefore, in the present preferred embodiment, the shapes of the insulating layers  76 E,  77 E,  84 E, and  85 E for insulating and separating the portions of the Z fixed electrode  71 E and the Z movable electrode  72 E from other portions are formed as columnar portions  29 E by etching the base substrate  7 E whose crystal structure is neat (the step of  FIG. 39A ). Next, the columnar portions  29 E are altered into insulating films by thermal oxidization (the step of  FIG. 39B ). Next, a polysilicon layer  22 E is formed around the insulating films (the step from  FIG. 39C  to  FIG. 39D ), and the polysilicon layer  22 E is etched into the shapes of the Z fixed electrode  71 E and the Z movable electrode  72 E (the step of  FIG. 39H ). Specifically, the shapes of the insulating layers  76 E,  77 E,  84 E, and  85 E are formed by etching the base substrate  7 E, so that as compared with the method for forming the isolation joints in Patent Document 1, the insulating layers with higher strength can be formed in a shorter time (for example, the etching rate is approximately 5 μm to 10 μm/min.). 
     As shown in  FIG. 39C , after polysilicon is epitaxially grown so as to completely cover the insulating layers  76 E,  77 E,  84 E and  85 E, by applying CMP to the grown polysilicon, the thickness of the polysilicon layer  22 E is adjusted. Therefore, as compared with the case where the thickness of the polysilicon layer  22 E is adjusted by considering the growth time of polysilicon from the seed film, etc., the polysilicon layer  22 E having a thickness equal to the height of the insulating films formed by the columnar portions  29 E can be easily formed. Accordingly, the first comb tooth portions  74 E and the opposed portions  75 E of the Z fixed electrode  71 E and the base end portions  81 E, the tip end portions  82 E, and the intermediate portions  83 E of the Z movable electrode  72 E can be reliably insulated from other portions of the polysilicon layer  22 E, respectively. 
     As shown in  FIG. 39F , previous to the step of molding the polysilicon layer  22 E into the Z fixed electrode  71 E and the Z movable electrode  72 E (the step of  FIG. 39H ), wirings  86 E to  89 E are formed on the polysilicon layer  22 E. Before molding the electrodes  71 E and  72 E, the space on the polysilicon layer  22 E can be effectively used. Even if a slight difference occurs between the actually formed pattern of the wirings  86 E to  89 E and the designed specification formation pattern, by correcting the molded pattern of the electrodes  71 E and  72 E by considering the difference, a sensor as designed can be manufactured finally. 
     The description of the operation and effects of the X-axis sensor  10 E and the Y-axis sensor  11 E is omitted, however, the same operation and effects as those of the above-described Z-axis sensor  12 E can be obtained with the X-axis sensor  10 E and the Y-axis sensor  11 E according to the present preferred embodiment by arranging these as shown in  FIG. 34  to  FIG. 36 . 
     The MEMS package  1 E according to the present preferred embodiment includes the X-axis sensor  10 E, the Y-axis sensor  11 E, and the Z-axis sensors  12 E, so that the MEMS package can accurately detect angular velocities applied around three axes (X axis, Y axis, and Z axis) orthogonal to each other in a three-dimensional space. 
     The fifth preferred embodiment of the present invention is described above, however the present invention can also be carried out in other embodiments. 
     For example, the MEMS package  1 E may include an acceleration sensor instead of or in addition to the angular velocity sensor  3 E. The acceleration sensor can be manufactured, for example, by omitting the drive portions in the sensors  10 E to  12 E shown in  FIG. 34  to  FIG. 38 . For example, as shown in  FIG. 40 , a Z-axis acceleration sensor  90 E that detects acceleration applied in the Z-axis direction can be manufactured by omitting the opposed portions  75 E of the Z fixed electrode  71 E and the tip end portions  82 E of the Z movable electrode  72 E that function as drive portions and the wirings  87 E and  89 E connected to these portions in the Z-axis sensor  12 E shown in  FIG. 37 . 
     In the Z-axis acceleration sensor  90 E, the variation in size (thicknesses T 1  and T 2  and widths W 1  and W 2 ) of the Z fixed electrode  71 E and the Z movable electrode  72 E can be reduced. 
     Therefore, in the Z-axis acceleration sensor  90 E, the opposing area between the first comb tooth portions  74 E and the intermediate portions  83 E of the second comb tooth portions  79 E according to the thicknesses T 1  and T 2  of the Z fixed electrode  71 E and the Z movable electrode  72 E, and the electrode-to-electrode distance d according to the widths W 1  and W 2  of the Z fixed electrode  71 E and the Z movable electrode  72 E can be maintained constantly. Therefore, a change in capacitance between the Z movable electrode  72 E and the Z fixed electrode  71 E caused by a change in the opposing area and/or electrode-to-electrode distance d can be accurately detected. As a result, based on the change in capacitance, acceleration can be accurately detected. 
     The material of the base insulating layer  21 E is not limited to SiO 2 , and may be other materials (for example, SiN, etc.) having etching selectivity to Si. 
     Preferred embodiments of the present invention are described in detail above, however these are only detailed examples used for clarifying the technical contents of the present invention, and the present invention should not be interpreted as being limited to these detailed examples, and the spirit and scope of the present invention are limited only by the claims attached hereto. 
     The above-described features grasped from the disclosure of the first to fifth preferred embodiments described above may be combined with each other even among different preferred embodiments. The components described in the preferred embodiments may be combined within the scope of the present invention. 
     The present application corresponds to Japanese Patent Application No. 2010-212341 filed in Japan Patent Office on Sep. 22, 2010, Japanese Patent Application No. 2010-232910 filed in Japan Patent Office on Oct. 15, 2010, Japanese Patent Application No. 2010-271982 filed in Japan Patent Office on Dec. 6, 2010, Japanese Patent Application No. 2010-277213 filed in Japan Patent Office on Dec. 13, 2010, and Japanese Patent Application No. 2010-277214 filed in Japan Patent Office on Dec. 13, 2010, the whole disclosures of which are incorporated herein by reference.