Patent Publication Number: US-2010116057-A1

Title: Mems sensor and method of manufacturing the same

Description:
TECHNICAL FIELD 
     The present invention relates to a sensor manufactured by a MEMS (Micro Electro Mechanical Systems) technique and a method of manufacturing the same. 
     PRIOR ART 
     A MEMS sensor, having been recently loaded on a portable telephone, is increasingly watched with interest. For example, a piezoresistive acceleration sensor for detecting the acceleration of a substance is known as a typical MEMS sensor. 
       FIG. 15  is a schematic perspective view showing the structure of a conventional piezoresistive acceleration sensor in a partially fragmented manner. 
     A conventional MEMS sensor  101  includes a frame  102 , a weight  103  and four beams  104 . 
     The frame  102  is in the form of a quadrangular ring (a frame) in plan view, and has a thickness of about 400 μm, for example. 
     The weight  103  is arranged on a region surrounded by the frame  102  at an interval from the frame  102 . The weight  103  is composed of a central columnar portion  105  in the form of a quadrangular column and four peripheral columnar portions  106  in the form of quadrangular columns provided on the periphery thereof. Each of the central columnar portion  105  and the peripheral columnar portions  106  has a thickness (height) identical to that of the frame  102 . The central columnar portion  105  is arranged on a central portion of the region surrounded by the frame  102 , so that the outer peripheral edges thereof are parallel to the inner peripheral edges (the inner surfaces) of the frame  102  in plan view. The peripheral columnar portions  106  are arranged one by one on extensions of respective diagonal lines toward both sides on the upper surface of the central columnar portion  105 . Single corners of the side surfaces of the peripheral columnar portions  106  are connected to the corners of the side surfaces of the central columnar portion  105  respectively. Thus, the central columnar portion  105  and the four peripheral columnar portions  106  integrally constitute the weight  103  having the same thickness as the frame  102 . 
     Each beam  104  extends between each pair of peripheral columnar portions  106  adjacent to each other, parallelly to the side surfaces of the peripheral columnar portions  106  at intervals. An end of the beam  104  is connected to the frame  102 , while another end thereof is connected to the central columnar portion  105 . The beam  104  has a thickness of about 7 μm, for example, to be twistable and deflectable due to the thickness. Thus, the four beams  104  support the weight  103  to be vibratile with respect to the frame  102 . 
     A plurality of piezoresistive elements are arranged on the four beams  104 , although the same are not shown. 
     When acceleration acts on the MEMS sensor  101  and the weight  103  vibrates, the beams  104  are distorted. Due to the distortion of the beams  104 , stress acts on the piezoresistive elements on the beams  104 , to change the resistivity of the piezoresistive elements. When the change of the resistivity of each piezoresistive element is extracted as a signal, therefore, the acceleration acting on the MEMS sensor  101  (the weight  103 ) can be detected on the basis of the signal. 
     The MEMS sensor  101  is manufactured by employing a substrate having a multilayer structure of a silicon back layer having a thickness of 400 μm, a silicon oxide layer having a thickness of 1 μm and a silicon front layer having a thickness of 7 μm. In the steps of manufacturing the same, the silicon front layer is first selectively etched through the silicon oxide layer serving as an etching stopper, whereby a front-side groove surrounding a portion for forming each peripheral columnar portion  106  is formed in the silicon front layer. Then, the silicon back layer is selectively etched through the silicon oxide layer serving as an etching stopper, whereby a back-side groove opposed to a portion for forming each beam  104  and the front-side groove is formed in the silicon back layer. A portion of the silicon oxide layer exposed through the back-side groove is etched, whereby the beam  104  consisting of the silicon front layer is formed while the frame  102  and the weight  103  consisting of the silicon back layer, the silicon oxide layer and the silicon front layer are formed. Consequently, the MEMS sensor  101  is obtained.
     Patent Document 1: Japanese Unexamined Patent Publication No. 2005-351716   

     DISCLOSURE OF THE INVENTION 
     Problems to be Solved  
     Thus, in order to obtain the MEMS sensor  101 , the silicon back layer and the silicon oxide layer must be removed from portions opposed to the beams  104  while leaving the same in the portions for forming the frame  102  and the weight  103 . The portions of the silicon back layer and the silicon oxide layer opposed to the beams  104  are not exposed from the front-side grooves formed in the silicon front layer, and hence removal of the portions can be attained only by the etching from the side of the silicon back layer. Therefore, the substrate must be etched from both of the sides of the silicon front layer and the silicon back layer, and it takes time to manufacture the MEMS sensor  101 . 
     Accordingly, an object of the present invention is to provide an easily manufacturable MEMS sensor and a method of manufacturing the same. 
     Solutions to the Problems  
     A MEMS sensor according to an aspect of the present invention includes a base layer, and a deformation portion provided on the base layer at an interval from the base layer and deformed by external force, while the deformation portion is made of an organic material. 
     The MEMS sensor is obtained by stacking a sacrificial layer and an organic material layer in this order on the base layer, forming a through-hole in the organic material layer and etching (isotropically etching) the sacrificial layer through the through-hole, for example. 
     Therefore, the MEMS sensor can be easily manufactured without etching the base layer. 
     The base layer may not be etched, whereby the MEMS sensor can be loaded on a semiconductor substrate provided with elements such as CMOS devices. In other words, the MEMS sensor can be provided on a common semiconductor substrate mixedly with elements such as CMOS devices. 
     The MEMS sensor may include a weight provided on a surface of the deformation portion opposed to the base layer. 
     The MEMS sensor may further include a frame supporting the deformation portion on the periphery of the weight, a resistive conductor arranged on the deformation portion, and a wire arranged on the deformation portion and connected to the resistive conductor. In other words, the MEMS sensor may be a piezoresistive acceleration sensor including a deformable beam made of an organic material, a weight made of the organic material and integrally formed with the beam, a frame supporting the beam on the periphery of the weight, a resistive conductor arranged on the beam, and a wire arranged on the beam and connected to the resistive conductor. 
     The MEMS sensor having this structure can be obtained by a manufacturing method including the steps of forming a sacrificial layer on a base layer, forming a recess in the surface of the sacrificial layer, forming an organic material layer to fill up the recess and to cover the surface of the sacrificial layer, forming a wire on the organic material layer, forming a resistive conductor connected with the wire on the organic material layer, forming a groove along the periphery of the recess in plan view by etching the organic material layer from the surface side of the organic material layer, and forming a beam and a weight consisting of the organic material layer by etching the sacrificial layer through the groove. According to the manufacturing method, the MEMS sensor can be easily manufactured without etching the base layer. 
     The weight may be made of the organic material, and may be integrally formed with the deformation portion. 
     The MEMS sensor may include a first electrode provided on a surface of the base layer opposed to the deformation portion, and a second electrode provided on a surface of the deformation portion opposed to the base layer and opposed to the first electrode at an interval. 
     The first electrode and the second electrode constitute a capacitor whose capacitance changes in response to a change in the interval therebetween. When a physical quantity (acceleration, for example) in a prescribed direction is caused in the MEMS sensor (a substance loaded with the MEMS sensor) or a physical quantity (a pressure such as a sound pressure, for example) in a prescribed direction acts on the MEMS sensor, the deformation portion is deformed and the second electrode is thereby displaced, the interval between the first electrode and the second electrode changes. Thus, the capacitance of the capacitor constituted of the first electrode and the second electrode changes, and hence the physical quantity in the prescribed direction can be detected on the basis of the change of the capacitance. Therefore, the MEMS sensor including the first electrode and the second electrode can be employed as a capacitance type acceleration sensor, and can be employed as a microphone. 
     The MEMS sensor including the first electrode and the second electrode can be obtained by a manufacturing method including the steps of forming a first electrode made of a first conductive material on a base layer, forming a sacrificial layer made of a material different from the first conductive material on the first electrode, forming a second electrode made of a second conductive material identical to or different from the first conductive material on the sacrificial layer, forming an organic material layer made of an organic material on the second electrode, forming a through-hole penetrating the organic material layer and the second electrode in the stacking direction thereof, and forming a space between the first electrode layer and the second electrode by etching the sacrificial layer through the through-hole. According to the manufacturing method, the MEMS sensor can be easily manufactured without etching the base layer. 
     The MEMS sensor including the first electrode and the second electrode may include a protrusion provided on the surface of the deformation portion opposed to the base layer. 
     The protrusion may be made of the organic material, and may be integrally formed with the deformation portion. 
     The organic material may be polyimide. 
     The foregoing and other objects, features and effects of the present invention will become more apparent from the following detailed description of the embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic plan view of a MEMS sensor according to an embodiment of the present invention. 
         FIG. 1B  is a schematic sectional view taken along a line B-B shown in  FIG. 1A . 
         FIG. 2A  is a schematic plan view in the process of manufacturing the MEMS sensor shown in  FIG. 1 . 
         FIG. 2B  is a schematic sectional view taken along a line B-B shown in  FIG. 2A . 
         FIG. 3A  is a schematic plan view showing a step subsequent to  FIG. 2A . 
         FIG. 3B  is a schematic sectional view taken along a line B-B shown in  FIG. 3A . 
         FIG. 4A  A schematic plan view showing a step subsequent to  FIG. 3 . 
         FIG. 4B  is a schematic sectional view taken along a line B-B shown in  FIG. 4A . 
         FIG. 5  A schematic sectional view showing a step subsequent to  FIG. 4 . 
         FIG. 6  A schematic sectional view showing a step subsequent to  FIG. 5 . 
         FIG. 7A  A schematic plan view showing a step subsequent to  FIG. 6 . 
         FIG. 7B  is a schematic sectional view taken along a line B-B shown in  FIG. 7A . 
         FIG. 8  is a schematic sectional view of a MEMS sensor according to another embodiment of the present invention. 
         FIG. 9  is a schematic sectional view in the process of manufacturing the MEMS sensor shown in  FIG. 8 . 
         FIG. 10  is a schematic sectional view showing a step subsequent to  FIG. 9 . 
         FIG. 11  is a schematic sectional view showing a step subsequent to  FIG. 10 . 
         FIG. 12  is a schematic sectional view showing a step subsequent to  FIG. 11 . 
         FIG. 13  is a schematic sectional view showing a step subsequent to  FIG. 12 . 
         FIG. 14  is a schematic sectional view showing a step subsequent to  FIG. 13 . 
         FIG. 15  A schematic perspective view showing the structure of a conventional MEMS sensor in a partially fragmented manner. 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS 
       1  MEMS sensor 
       2  base layer 
       3  frame 
       4  beam 
       5  weight 
       6  resistive conductor 
       7  wire 
       8  supporting portion 
       9  beam body portion 
       21  SiN layer 
       22  recess 
       23  organic material layer 
       26  groove 
       51  MEMS sensor 
       52  base layer 
       53  first electrode 
       54  diaphragm 
       55  protrusion 
       56  second electrode 
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of the present invention are now described with reference to the attached drawings. 
       FIG. 1A  is a schematic plan view of a MEMS sensor according to an embodiment of the present invention, and  FIG. 1B  is a schematic sectional view of the MEMS sensor taken along a line B-B shown in  FIG. 1A . 
     A MEMS sensor  1  is a piezoresistive acceleration sensor, and includes abase layer  2 , a frame  3 , a beam  4 , weights  5 , resistive conductors  6  and wires  7 . 
     The base layer  2  is made of SiO 2  (silicon oxide). The base layer  2  is in the form of a quadrangle in plan view, and has a thickness of 0.1 to 3 μm. 
     The frame  3 , the beam  4 , the weights  5 , the resistive conductors  6  and the wires  7  are provided on the base layer  2 . 
     The frame  3  is made of SiN (silicon nitride). The frame  3  is in the form of a quadrangular ring (a frame) along the peripheral edges of the base layer  2  in plan view, and has a thickness of 1 to 10 μm. 
     The beam  4  and the weights  5  are made of an organic material (polyimide, for example), and integrally formed. 
     The beam  4  integrally includes a supporting portion  8  in the form of a quadrangular ring in plan view supported by the frame  3  and a beam body portion  9  in the form of a cross in plan view supported by the supporting portion  8 . The forward ends of the beam body portion  9  are connected to the centers of the sides of the supporting portion  8  respectively. Thus, the beam  4  has four quadrangular openings partitioned by the supporting portion  8  and the beam body portion  9 . The beam  4  has a thickness of 1 to 10 μm, so that the beam body portion  9  is twistable and deflectable due to the thickness. 
     Each weight  5  is arranged in each opening of the beam  4 . The weight  5  is in the form of a generally quadrangular column, whose upper surface is flush with the upper surface of the beam  4 , having a thickness (height) of 1 to 10 μm. The side surfaces of the weight  5  are parallel to the peripheral edges of the opening with clearances. One of four corners formed by the side surfaces of the weight  5  is connected to the central portion of the beam body portion  9  of the beam  4 . Thus, the weight  5  is supported by the beam  4  (the beam body portion  9 ) in a state not in contact with the base layer  2  and the frame  3 . 
     A laminate  10  of a Ti (titanium) layer, a TiN (titanium nitride) layer and an Al (aluminum) —Cu (copper) alloy layer is stacked on the beam  4 . The laminate  10  has end portions arranged on the supporting portion  8 , extends along the beam body portion  9 , and is in the form of a cross in plan view as a whole. The lowermost Ti layer and the TiN layer provided thereon are continuously formed. On the other hand, the uppermost Al—Cu alloy layer is broken on twelve portions, for example, to be intermittently formed. Thus, the Ti layer and the TiN layer are partially exposed on the broken portions (removed portions) of the Al—Cu alloy layer so that the exposed portions form the resistive conductors  6 , while the Al—Cu alloy layer forms the wires  7  connected to the resistive conductors  6 . 
     The outermost surface of the MEMS sensor  1  is covered with a protective film  11  made of polyimide, for example. The protective film  11  is provided with pad openings  12  exposing end portions of the wires  7  formed along the cross in plan view as pads for external connection respectively. The protective film  11  is also provided with grooves  13  communicating with the clearances between the beam  4  and the weights  5 . 
     When acceleration acts on the MEMS sensor  1  and the weights  5  vibrate, distortion (twist and/or deflection) is caused on the beam body portion  9  of the beam  4 . The resistive conductors  6  on the beam body portion  9  are expanded/contracted due to the distortion of the beam body portion  9 , and the resistance values of the resistive conductors  6  change. The changes of the resistance values are extracted as signals through the pads, so that the directions (triaxial directions) and the magnitudes of the acceleration acting on the weights  5  (the MEMS sensor  1 ) can be detected on the basis of the signals. 
       FIGS. 2A to 7B  are diagrams for illustrating a method of manufacturing the MEMS sensor shown in  FIGS. 1A and 1B . 
     First, an SiN layer  21  as a sacrificial layer made of the material for the frame  3  is formed on the base layer  2  by P-CVD (Plasma Chemical Vapor Deposition), as shown in  FIGS. 2A and 2B .  FIG. 2A  is a schematic plan view showing the state where the SiN layer  21  is formed on the base layer  2 , and  FIG. 2B  is a schematic sectional view of the structure shown in  FIG. 2A  taken along a line B-B. 
     Then, a resist film having openings in portions corresponding to portions for forming the weights  5  respectively is formed on the SiN layer  21 . Then, the SiN layer  21  is etched by RIE (Reactive Ion Etching) through the resist film serving as a mask. Consequently, four recesses  22  are formed in the surface of the SiN layer  21 , as shown in  FIGS. 3A and 3B .  FIG. 3A  is a schematic plan view showing the state where the recesses  22  are formed in the SiN layer  21 , and  FIG. 3B  is a schematic sectional view of the structure shown in  FIG. 3A  taken along a line B-B. 
     Thereafter the organic material (polyimide, for example) which is the material for the beam  4  and the weights  5  is applied onto the overall region of the SiN layer  21  having the recesses  22 , whereby an organic material layer  23  made of the organic material is formed, as shown in  FIGS. 4A and 4B . The organic material layer  23  fills up the recesses  22  and covers the overall region of the surface of the SiN layer  21 , while the surface thereof is generally planar.  FIG. 4A  is a schematic plan view showing the state where the organic material layer  23  is formed on the SiN layer  21 , and  FIG. 4B  is a schematic sectional view of the structure shown in  FIG. 4A  taken along a line B-B. 
     Then, a Ti layer/TiN layer  24  and an Al—Cu alloy layer  25  are formed on the organic material layer  23  in this order by sputtering, as shown in  FIG. 5 . 
     Thereafter the Ti layer/TiN layer  24  and the Al—Cu alloy layer  25  are patterned, whereby the resistive conductors  6  and the wires  7  are formed, as shown in  FIG. 6 . 
     Then, the material for the protective film  11  is applied onto the organic material layer  23  provided with the resistive conductors  6  and the wires  7 , as shown in  FIGS. 7A and 7B . Then, the layer made of the material for the protective film  11  is partially removed, whereby the pad openings  12  are formed. Further, the layer made of the material for the protective film  11  and the organic material layer  23  are partially removed, whereby the grooves  13  corresponding to the clearances between the beam  4  and the weights  5  are formed to be along the outer peripheries of the recesses  22  in plan view respectively. Thus, the organic material layer  23  forms the beam  4  and the weights  5 . The grooves  13  are so formed that the surface of the SiN layer  21  is partially exposed through the grooves  13 . 
     Thereafter portions of the SiN layer  21  located under the beam  4  and the weights  5  are removed by CDE (Chemical Dry Etching) from the side of the protective film  11  through the grooves  13 . The etching of the SiN layer  21  by CDE is continued until the portions of the SiN layer  21  located under the weights  5  are entirely removed. At this time, the base layer  2  made of SiO 2 , having an extremely small etching rate as compared with the SiN layer  21 , functions as an etching stopper layer. Consequently, the SiN layer  21  is patterned into the frame  3 , and the MEMS sensor  1  having the structure shown in  FIG. 1  is obtained. 
     As hereinabove described, the recesses  22  are formed in the surface of the SiN layer  21 , and the organic material layer  23  is thereafter formed on the SiN layer  21  to fill up the recesses  22  and to cover the surface of the SiN layer  21 . Then, the resistive conductors  6  and the wires  7  are formed on the organic material layer  23 . Further, the organic material layer  23  is etched from the surface side of the organic material layer  23  along the outer peripheries of the recesses  22  in plan view. Thus, the beam  4  and the weights  5  consisting of the organic material layer  23  are formed. Then, the SiN layer  21  is etched through the grooves  13  formed by the etching, whereby the frame  3  supporting the beam  4  on the peripheries of the weights  5  is formed. 
     Thus, the MEMS sensor  1  having the structure shown in  FIG. 1  can be easily manufactured without etching the base layer  2 . 
     The base layer  2  may not be etched, whereby the MEMS sensor  1  can be loaded on a semiconductor substrate provided with elements such as CMOS devices. In other words, the MEMS sensor  1  can be provided on a common semiconductor substrate mixedly with elements such as CMOS devices. 
     While the case where SiO 2  is employed as the material for the base layer  2  and SiN is employed as the material for the frame  3  has been described by way of example, SiN may be employed as the material for the base layer  2 , and SiO 2  may be employed as the material for the frame  3 . In this case, etching of an SiO 2  layer made of the material for the frame  3  can be achieved by wet etching employing hydrofluoric acid, for example. 
     The material for the base layer  2  may simply be prepared from a material increasing a selection ratio in etching (etching for forming the frame  3 ) of the layer made of the material for the frame  3 , and Al can be illustrated when the frame  3  is made of SiO 2 . 
     When the substrate loaded with the MEMS sensor  1  has a layer employing the material increasing the selection ratio in the etching of the layer made of the material for the frame  3  on the outermost layer (the layer in contact with the MEMS sensor  1 ), the base layer  2  can be omitted. 
     When the quantity of the etching for forming the frame  3  is controlled by time, the base layer  2  and the frame  3  may be made of the same material (SiO 2 , for example). 
       FIG. 8  is a schematic sectional view of a MEMS sensor according to another embodiment of the present invention. 
     A MEMS sensor  51  is a microphone, and includes a base layer  52 , a first electrode  53 , a diaphragm  54 , a protrusion  55  and a second electrode  56 . 
     The base layer  52  is made of SiO 2  (silicon oxide). The base layer  52  is in the form of a quadrangle in plan view, and has a thickness of 0.1 to 3 μm. 
     The first electrode  53 , the diaphragm  54 , the protrusion  55  and the second electrode  56  are provided on the base layer  52 . 
     The first electrode  53  is made of Al (aluminum). The base layer  52  is formed on the surface of the base layer  52  as a film having a thickness of 0.3 to 2.0 μm. 
     The diaphragm  54  and the protrusion  55  are made of an organic material (polyimide, for example), and integrally formed. 
     The diaphragm  54  is in the form of a film having a thickness of 0.3 to 2.0 μm, and the peripheral edge portions thereof are supported by an unshown supporting portion. A space of 1 to 5 μm is formed between the diaphragm  54  and the base layer  52 . A central portion of the diaphragm  54  is vibratile (deformable) in the direction opposed to the base layer  52 . 
     The protrusion  55  is provided on the surface (the lower surface) of the diaphragm  54  opposed to the base layer  52 . The protrusion  55  is in the form of a generally quadrangular column having a thickness (height) of 1 to 20 μm, and a space of 1 to 10 μm is formed between the same and the base layer  52 . The protrusion  55  is so provided that the second electrode  56  described below can be prevented from coming into contact with the first electrode  53  in vibration of the diaphragm  54 . In other words, the protrusion  55  functions as a stopper regulating the quantity of vibration of the diaphragm  54 . Only one protrusion  55  may be formed, or a plurality of protrusions  55  may be formed. 
     The second electrode  56  is made of Al (aluminum). The second electrode  56  is formed on the surface of the diaphragm  54  opposed to the base layer  52  as a film having a thickness of 0.3 to 2.0 μm. Thus, the second electrode  56  is opposed to the first electrode  53  at an interval, and constitutes a capacitor whose capacitance changes in response to the interval. 
     When a sound pressure is input in the MEMS sensor  51 , the diaphragm  54  vibrates, whereby the second electrode  56  is displaced. The interval between the first electrode  53  and the second electrode  56  changes due to the displacement of the second electrode  56 , and the capacitance of the capacitor constituted of the first electrode  53  and the second electrode  56  changes. Therefore, the sound pressure input in the MEMS sensor  51  can be detected by extracting the change of the capacitance as a sound output signal. 
     A plurality of through-holes  57  are formed in the diaphragm  54  and the second electrode  56  to penetrate the same in the stacking direction. 
       FIGS. 9 to 14  are diagrams for illustrating a method of manufacturing the MEMS sensor shown in  FIG. 8 . 
     First, the first electrode  53  consisting of an Al film is formed on the surface of the base layer  52  by sputtering, as shown in  FIG. 9 . 
     Then, a sacrificial layer  58  made of SiN is formed on the first electrode  53  by P-CVD, as shown in  FIG. 10 . 
     Thereafter an Al film  59  is formed on the sacrificial layer  58  by sputtering, as shown in  FIG. 11 . 
     Then, a resist film having an opening in a portion corresponding to a portion for forming the protrusion is formed on the Al film  59 . Then, the Al film  59  and the sacrificial layer  58  are etched through the resist film serving as a mask. Consequently, a recess  60  dug from the surface of the Al film  59  up to an intermediate portion of the sacrificial layer  58  is formed, as shown in  FIG. 12 . 
     Thereafter the organic material (polyimide, for example) which is the material for the diaphragm  54  and the protrusion  55  is applied onto the overall region of the sacrificial layer  58  having the recess  22 , whereby an organic material layer  61  made of the organic material is formed, as shown in  FIG. 13 . The organic material layer  61  fills up the recess  60  and covers the overall region of the surface of the Al film  59 , while the surface thereof is generally planar. 
     Then, the organic material layer  61  and the Al film are selectively removed, whereby the plurality of through-holes  57  are formed, as shown in  FIG. 14 . Thus, the organic material layer  61  forms the diaphragm  54  and the protrusion  55 , while the Al film  59  forms the second electrode  56 . Further, the surface of the sacrificial layer  58  is partially exposed through the through-holes  57 . Portions of the sacrificial layer  58  located under the diaphragm  54  and the protrusion  55  are removed by CDE through the through-holes  57 . Consequently, the MEMS sensor  51  having the structure shown in  FIG. 8  is obtained. 
     Thus, the MEMS sensor  51  having the structure shown in  FIG. 8  can be easily manufactured without etching the base layer  52 . 
     The base layer  52  may not be etched, whereby the MEMS sensor  51  can be loaded on a semiconductor substrate provided with elements such as CMOS devices. In other words, the MEMS sensor  51  can be provided on a common semiconductor substrate mixedly with elements such as CMOS devices. 
     The MEMS sensor  51  can be used also as an acceleration sensor. When acceleration in the opposed direction of the first electrode  53  and the second electrode  56  is caused in the MEMS sensor  51 , the diaphragm  54  is deformed, whereby the second electrode  56  is displaced. The interval between the first electrode  53  and the second electrode  56  changes due to the displacement of the second electrode  56 , and the capacitance of the capacitor constituted of the first electrode  53  and the second electrode  56  changes. Therefore, the magnitude of the acceleration caused in the MEMS sensor  51  can be detected on the basis of the change of the capacitance. 
     While SiN has been illustrated as the material for the sacrificial layer  58 , the material for the sacrificial layer  58  is not restricted to SiN, but may simply be a material having an etching selection ratio with the material for the first electrode  53  and the second electrode  56 . 
     While Al has been illustrated as the material for the first electrode  53  and the second electrode  56 , a conductive material other than Al such as Cu or doped polysilicon may be employed. 
     While polyimide has been illustrated as the organic material, polyparaxylene or polyamide may be employed. 
     The present invention is not restricted to the acceleration sensor and the microphone, but also applicable to a gyro sensor for detecting the angular speed of a substance. 
     While the present invention has been described in detail by way of the embodiments thereof, it should be understood that these embodiments are merely illustrative of the technical principles of the present invention but not limitative of the invention. The spirit and scope of the present invention are to be limited only by the appended claims. 
     This application corresponds to Japanese Patent Application No. 2007-131831 filed with the Japan Patent Office on May 17, 2007, the disclosure of which is incorporated herein by reference.