Abstract:
A semiconductor device disclosed herein comprises a semiconductor layer which includes a first semiconductor region of a first conductivity type, a base region of a second conductivity type, and a plurality of second semiconductor regions of the first conductivity type; a gate wiring which is formed on the semiconductor layer via a first insulating film; a plurality of main electrodes which are electrically connected to the plurality of second semiconductor regions and which are insulated from the gate wiring, wherein the gate wiring is arranged between the main electrodes and upper surfaces of the main electrodes are higher than an upper surface of the uppermost layer of the gate wiring; and a connecting plate which is directly connected onto uppermost layers of the main electrodes.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims benefit of priority under 35 U.S.C. § 119 to Japanese Patent Applications No. 2002-213331, filed on Jul. 23, 2002, and No. 2002-295629, filed on Oct. 9, 2002, the entire contents of which are incorporated by reference herein.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a semiconductor device to which a semiconductor chip having a cell such as a MOS-type power device is incorporated.  
           [0004]    2. Related Art  
           [0005]    In recent years, scale-down is demanded from a power device such as a vertical MOSFET, and a reduction in the value of internal resistance (on-state resistance or the like) of the entire semiconductor device including the aforementioned device is also strongly demanded. FIG. 20 shows an example of a related semiconductor device. Here,  2001  denotes a semiconductor substrate,  2002  denotes a source electrode,  2003  denotes a lead frame,  2004  denotes a source wire,  2005  denotes a gate wire, and  2006  denotes a gate wiring.  
           [0006]    A lead-out wiring region and a cell forming region are provided on the surface of a semiconductor chip, and a cell such as a MOSFET is formed in the cell forming region. The source electrode  2002  and the lead frame  2003  are connected by a plurality of source wires  2004 . The source electrode is required to pass more current than a gate electrode, but since it is connected by the wires, the cross-sectional area of a current path is small, and hence the resistance value is high. To reduce this resistance value, there is a technique in which a reduction in on-state resistance is achieved by a structure in which the source electrode and the lead frame are connected by an almost platy conductive plate. Hereinafter, this almost platy conductive plate is called a strap. Moreover, the structure in which the source electrode and the lead frame are connected by the strap is called a strap structure. For example, in Japanese Patent Laid-open No. 2000-114445, a method of connecting a Cu strap onto an electrode on the surface of a semiconductor chip by an Ag paste as an adhesive is disclosed.  
           [0007]    This method has the following problem depending on conditions. Namely, if a temperature cycling test, one of common reliability tests of a semiconductor device, in which the semiconductor device is disposed under an environment with a wide range of temperature and a sharp temperature change, is repeated a plurality of times, there arises a problem that a fault such as cracking occurs in the vicinity of an interface since thermal efficient coefficients of an electrode member, the adhesive, and the strap are different from one another, whereby the life of the semiconductor device is shortened.  
           [0008]    As a technique to solve this problem, a method of directly connecting the strap to the electrode on the. surface of the semiconductor chip by ultrasonic bonding is newly proposed. FIG. 21 is a fragmentary sectional view of a related semiconductor device and shows a lead-out wiring region including a gate wiring and the like. It shows a region corresponding to the line A-A′ in FIG. 20, and it is a sectional view of a first lead-out wiring region sandwiched between source electrodes out of the lead-out wiring region. A device such as a MOSFET is formed in another cell forming region, and an N-type source region (not shown) is selectively formed on the surface of a P-type base region  2102  formed on a semiconductor substrate  2101 . A first insulating film  2103  is formed on the P-type base region  2102 . A first gate wiring  2104  is formed on part of the first insulating film  2103 , and the first gate wiring  2104  is connected to a gate electrode (not shown) such as the MOSFET formed in another cell forming region.  
           [0009]    A first interlayer dielectric  2106  is formed on a side surface and part of an upper surface of the first gate wiring  2104  for insulation from a source electrode  2105 . A second gate wiring  2107  made of Al (Aluminum) is formed on the upper surface of the first gate wiring  2104  on which the first interlayer dielectric  2106  is not formed. The source electrode  2105  is formed on the P-type base region  2102  and the N-type source region. An upper surface of the second gate wiring  2107  is formed higher than an upper surface of the source electrode  2105 . A protective film  2108  such as polyimide is formed on part of the source electrode  2105  and on the second gate wiring  2107 . The protective film  2108  is formed in order to prevent a short-circuit between the second gate wiring  2107  and a strap formed thereabove, a short-circuit between the second gate wiring  2107  and the source electrode  2105 , corrosion of Al, and the like. The source electrode  2105  is connected to a strap  2109  by ultrasonic bonding.  
           [0010]    [0010]FIG. 22 is a fragmentary sectional view of the related semiconductor device and shows another lead-out wiring region including the gate wiring and the like. It is a sectional view of a region corresponding to the line B-B′ in FIG. 20 and shows an outer peripheral region of the cell forming region out of the lead-out wiring region. It is a sectional view of a second lead-out wiring region in which a gate electrode and the lead frame are connected by the gate wire.  
           [0011]    A first insulating film  2202  is formed on a semiconductor substrate  2201 . A first gate wiring  2203  is formed on part of the first insulating film  2202 , and a first interlayer dielectric  2204  is formed on a side surface and part of an upper surface of the first gate wiring  2203 . A second gate wiring  2205  made of Al is formed on the upper surface of the first gate wiring  2203  on which the first interlayer dielectric  2204  is not formed, and an end portion of the second gate wiring  2205  is formed to extend onto the first insulating film  2202 . A wiring portion which extends onto the first insulating film  2202  is used as a gate electrode  2207 . A source electrode  2206  is formed apart from the gate electrode  2207 , and a protective film  2208  such as polyimide is formed on part of the source electrode  2206  and on part of the gate electrode  2207  in order to prevent a short-circuit between the gate electrode  2207  and the source electrode  2206  and corrosion of Al. The source electrode  2206  is connected to the strap by ultrasonic bonding, and the gate electrode  2207  is connected to the gate wire (not shown). A stopper region  2209  is formed in a surface region of an outer peripheral edge of the semiconductor substrate  2201 .  
           [0012]    [0012]FIG. 23 to FIG. 25 show a method of manufacturing a semiconductor device in the first and second lead-out wiring regions shown in FIG. 21 and FIG. 22. The cell forming region is omitted.  
           [0013]    As shown in FIG. 23, a P-type base region  2302  is formed on a semiconductor substrate  2301  in the first lead-out wiring region. Subsequently, first insulating films  2303   a  and  2303   b  are formed on the P-type base region  2302  and the semiconductor substrate  2301  of the first and second lead-out wiring regions, respectively. Polysilicon is deposited on the first insulating films  2303   a  and  2303   b  and etched to form first gate wirings  2304   a  and  2304   b  on part of each of the first insulating films  2303   a  and  2303   b  in the first and second lead-out wiring regions. Silicon nitride films are formed on upper surfaces and side surfaces of the first gate wirings  2304   a  and  2304   b  and etched to form first interlayer dielectrics  2305   a  and  2305   b  having slot portions such that part of each of the upper surfaces of the, first gate wirings  1204   a  and  1204   b  is exposed.  
           [0014]    Then, Al is deposited and etched to form a second gate wiring  2306   a  in the first lead-out wiring region and a gate electrode  2307  integrated with a second gate wiring  2306   b  in the second lead-out wiring region. A source electrode  2308  is formed in the cell forming region (only part of the source electrode is shown). The gate electrode  2307  formed in the second lead-out wiring region is formed on the first insulating film  2303   b . The source electrode  2308  is formed apart from the second gate wiring  2306   a  and the gate electrode  2307 . A stopper region  2309  is formed in a surface region of an outer peripheral edge of the second lead-out wiring region.  
           [0015]    Next, as shown in FIG. 24, polyimide  2310  is deposited in the first and second lead-out wiring regions.  
           [0016]    Thereafter, by applying a resist film and forming a resist pattern, a protective film such as covers the gate wiring and a protective film  2311  such that part of the upper surface of the gate electrode is exposed are formed as shown in FIG. 25. Subsequently, the strap (not shown) is formed on the cell forming region and the first lead-out wiring region, and the gate wire (not shown) is formed on the gate electrode  2307  formed in the second lead-out wiring region and connected to the lead frame.  
           [0017]    However, reliability to heat increases dramatically in ultrasonic bonding, but since the strap is bonded by applying ultrasonic waves to a predetermined region of the strap, if the ultrasonic waves are-applied to a region on the projecting gate wiring in the first lead-out wiring region, a large shock is applied to the protective film on the gate wiring. Consequently, the projecting gate wiring is crushed, and the gate wiring and the source electrode are deformed, which causes a problem that a short-circuit between the gate wiring and the source electrode occurs, or the protective film formed on the gate wiring deteriorates to cause a short-circuit between the strap and the gate wiring. The aforementioned problem does not arise unless the projecting upper-layer gate wiring with low resistance is formed in the upper portion, but there is a problem that the existence of the upper-layer gate wiring exerts a large influence on internal resistance, and if the upper-layer gate wiring is not formed, for example, a resistance value of approximately 1.5 Ω increases to 3 Ω which is almost twice. In a power MOSFET especially used for synchronous rectification in recent years, an increase in resistance value lowers conversion efficiency, and hence it is not suitable for this use.  
         SUMMARY OF THE INVENTION  
         [0018]    In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a semiconductor device, comprises  
           [0019]    a semiconductor layer which includes a first semiconductor region of a first conductivity type, a base region of a second conductivity type, and a plurality of second semiconductor regions of the first conductivity type;  
           [0020]    a gate wiring which is formed on the semiconductor layer via a first insulating film;  
           [0021]    a plurality of main electrodes which are electrically connected to the plurality of second semiconductor regions and which are insulated from the gate wiring, wherein the gate wiring is arranged between the main electrodes and upper surfaces of the main electrodes are higher than an upper surface of the uppermost layer of the gate wiring; and  
           [0022]    a connecting plate which is directly connected onto uppermost layers of the main electrodes.  
           [0023]    According to another aspect of the present invention, a semiconductor device, comprises:  
           [0024]    a semiconductor layer which includes a first semiconductor region of a first conductivity type, a base region of a second conductivity type, and a cell forming region in which a plurality of second semiconductor regions of the first conductivity type are formed;  
           [0025]    a first gate electrode which is formed in the cell forming region and controls continuity/non-continuity between the first semiconductor region and the second semiconductor region;  
           [0026]    a plurality of main electrodes which are electrically connected to the plurality of second semiconductor regions respectively and which are formed at predetermined intervals in the cell forming region on the semiconductor layer;  
           [0027]    a gate wiring which is formed on the semiconductor layer between the plurality of main electrodes via a first insulating film and which leads out the first gate electrode to an outer peripheral region of the cell forming region, wherein upper surfaces of the uppermost layers of the plurality of main electrodes are higher than an upper surface of the uppermost layer of the gate wiring; and  
           [0028]    a first connecting plate which is directly connected onto the plurality of main electrodes.  
           [0029]    According to a further aspect of the present invention, a semiconductor device, comprises:  
           [0030]    a first semiconductor layer of a first conductivity type;  
           [0031]    a second semiconductor layer of a second conductivity type which is formed on the first semiconductor layer;  
           [0032]    a first semiconductor region of the first conductivity type which is formed in a first cell forming region in the second semiconductor layer;  
           [0033]    a second semiconductor region of the first conductivity type which is formed in a second cell forming region in the second semiconductor layer;  
           [0034]    a first gate electrode which is formed in the first cell forming region and controls continuity/non-continuity between the first semiconductor region and the first semiconductor layer;  
           [0035]    a second gate electrode which is formed in the second cell forming region and controls continuity/non-continuity between the second semiconductor region and the first semiconductor layer;  
           [0036]    a first main electrode which is electrically connected to the first semiconductor region and formed in the first cell forming region on the second semiconductor layer;  
           [0037]    a second main electrode which is electrically connected to the second semiconductor region and formed in the second cell forming region on the second semiconductor layer;  
           [0038]    a gate wiring which is formed on the second semiconductor layer between the first main electrode and the second main electrode via a first insulating film and which leads out the first and second gate electrodes to an outer peripheral region of the first and second cell forming regions, wherein an upper surface of the uppermost layer of the first main electrode and an upper surface of the uppermost layer of the second main electrode are higher than an upper surface of the uppermost layer of the gate wiring; and  
           [0039]    a first connecting plate which is directly connected onto the first main electrode and the second main electrode. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]    [0040]FIG. 1 is a fragmentary sectional view taken along the line A-A′ of a semiconductor device in FIG. 8 according to a first embodiment;  
         [0041]    [0041]FIG. 2 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the first embodiment;  
         [0042]    [0042]FIG. 3 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the first embodiment;  
         [0043]    [0043]FIG. 4 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the first embodiment;  
         [0044]    [0044]FIG. 5 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the first embodiment;  
         [0045]    [0045]FIG. 6 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the first embodiment;  
         [0046]    [0046]FIG. 7 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the first embodiment;  
         [0047]    [0047]FIG. 8 is a plan view of the semiconductor device according to the first embodiment;  
         [0048]    [0048]FIG. 9 is a fragmentary sectional view taken along the line C-C′ of each of semiconductor devices in FIG. 8 and FIG. 16 according to the first embodiment and a third embodiment;  
         [0049]    [0049]FIG. 10 is a fragmentary sectional view of a semiconductor device according to a second embodiment;  
         [0050]    [0050]FIG. 11 is a fragmentary sectional view taken along the line A-A′-B-B′ of the semiconductor device in FIG. 16 according to the third embodiment;  
         [0051]    [0051]FIG. 12 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the third embodiment;  
         [0052]    [0052]FIG. 13 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the third embodiment;  
         [0053]    [0053]FIG. 14 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the third embodiment;  
         [0054]    [0054]FIG. 15 is a fragmentary sectional view showing one step of the process of manufacturing the semiconductor device according to the third embodiment;  
         [0055]    [0055]FIG. 16 is a plan view of the semiconductor device according to the third embodiment;  
         [0056]    [0056]FIG. 17 is a diagram showing a layout of the semiconductor device according to the third embodiment;  
         [0057]    [0057]FIG. 18A and FIG. 18B are diagrams showing other layouts of the semiconductor device according to the third embodiment;  
         [0058]    [0058]FIG. 19 is a fragmentary sectional view of another semiconductor device according to the third embodiment;  
         [0059]    [0059]FIG. 20 is a plan view of a related semiconductor device;  
         [0060]    [0060]FIG. 21 is a fragmentary sectional view of the related semiconductor device;  
         [0061]    [0061]FIG. 22 is another fragmentary sectional view of the related semiconductor device;  
         [0062]    [0062]FIG. 23 is a fragmentary sectional view showing one step of the process of manufacturing the related semiconductor device;  
         [0063]    [0063]FIG. 24 is a fragmentary sectional view showing one step of the process of manufacturing the related semiconductor device;  
         [0064]    [0064]FIG. 25 is a fragmentary sectional view showing one step of the process of manufacturing the related semiconductor device; and  
         [0065]    [0065]FIG. 26A and FIG. 26B are diagrams showing examples of a layout of the related semiconductor device. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0066]    Embodiments will be described in detail below.  
         [0067]    (First Embodiment)  
         [0068]    First, a semiconductor device of the first embodiment will be explained with reference to FIG. 1 to FIG. 8.  
         [0069]    In this embodiment, the explanation is given with a MOSFET and an IGBT as its examples. FIG. 1 is a sectional view taken along the line A-A′ in FIG. 8. As shown in FIG. 1, a first insulating film  103  is formed, for example, on a P-type base region  102  of a lead-out wiring region which is formed on an N-type semiconductor substrate  101  and sandwiched between cell forming regions. A first gate wiring  104  is formed on the first insulating film  103 .  
         [0070]    A trench  105  is formed perpendicular and parallel to the first gate wiring  104  in the P-type base region  102  of the cell forming region. The trench  105  has an off set mesh trench structure. Incidentally, FIG. 1 is a fragmentary sectional view of a region in which the trench  105  is formed parallel to the first gate wiring  104 . A gate insulating film  106  is formed in the trench  105 , and a trench gate electrode  107  is buried in the trench  105  in such a manner as to touch the gate insulating film  106 . An N-type source region  108  is formed on the surface of the P-type base region  102  around the trench  105 . The N-type source region  108  is not formed around the trench  105  on the lead-out wiring region side.  
         [0071]    A cell formed in the cell forming region functions as a MOSFET if an N + -type drain region is formed under the semiconductor substrate  101  and a drain electrode is formed so as to touch the N + -type drain region, and functions as an IGBT (Insulated Gate Bipolar Transistor) if a P + -type collector region is formed under the semiconductor substrate  101  and a collector electrode is formed so as to touch the P + -type collector region. The cell formed in the cell forming region is not limited to the above. The structure of the cell is not limited to a trench type, and may be a planer type.  
         [0072]    The first gate wiring  104  and the trench gate electrode  107  are formed of a conductive material such as polysilicon and electrically connected to each other in another region (not shown).  
         [0073]    A first interlayer dielectric  109  such as a UDO (Undoped Oxide) or a BPSG is formed on a side surface and part of an upper surface of the first gate wiring  104 . On the first gate wiring  104  on which the first interlayer dielectric  109  is not formed, a second gate wiring  110  formed of a conductive material such as Al is formed and used as a lead-out wiring for the first gate wiring  104  and the trench gate electrode  107 . The first insulating film  103  and the first interlayer dielectric  109  may be integrally formed by an insulating film made of the same material. A second interlayer dielectric  111  is formed on the trench gate electrode  107 . The second interlayer dielectric  111  may be completely buried in the trench  105 .  
         [0074]    A first source electrode  112  such as Al is formed on the P-type base region  102 and the N-type source region  108 . The first source electrode  112  is formed so as to have a large area, which leads to a reduction in resistance. The first source electrode  112  is formed to be insulated from the first gate wiring  104  by the first interlayer dielectric  109  and insulated from the trench gate  107  by the second-interlayer dielectric  111 . On part of an upper surface of the first source electrode  112  and a side surface and an upper surface of the second gate wiring  110 , a second insulating film  113  is formed in order to, when an almost platy connecting plate (here called a strap) is connected by ultrasonic bonding, prevent a short-circuit between the second gate wiring  110  and the strap and a short-circuit between the first source electrode  112  and the second gate wiring  110 .  
         [0075]    Although the second insulating film  113  is also formed on part of the upper surface of the first source electrode  112 , it may not be formed thereon. However, by forming the insulating film to extend onto part of the upper surface of the first source electrode  112  as described above, a short-circuit fault caused by misalignment in patterning can be prevented, whereby a device with high yield and high reliability can be manufactured. The second insulating film  113  is composed of a silicon oxide film, a silicon nitride film, or a stacked film thereof. It is desirable to use an insulating film with a certain degree of hardness as the second insulating film  113  since an electrode layer is formed thereon. The thickness of the second insulating film  113  is preferably 2 μm to 4 μm.  
         [0076]    A second source electrode  114  such as Al is formed on the first source electrode  112  and the second insulating film  113  which is formed on the first source electrode  112 . The second gate wiring  110  and the second source electrode  114  are arranged with a gap  110   a  between them. The second source electrode  114  is formed thicker than the first source electrode  112  on the N-type source region  108 .  
         [0077]    Deterioration such as deformation in an interface between different kinds of materials and an increase in resistance can be prevented by forming the first source electrode  112  and the second source electrode  114  out of the same conductive material.  
         [0078]    Moreover, in this embodiment, an upper surface of the second source electrode  114  is formed higher than an upper surface of the second gate wiring  110 . The upper surface of the second source electrode  114  may be on the same level with the upper surface of the second insulating film  113  on the second gate wiring  110 . However, it is preferable that the upper surface of the second source electrode  114  be formed higher than the upper surface of the second insulating film  113  on the second gate wiring  110 .  
         [0079]    A strap  115  which connects with the second source electrode  114  is formed on the second source electrode  114 . The strap  115  is a connecting plate, for example, made of Al. The strap  115  is connected, for example, to a lead frame (not shown) for connection to the outside.  
         [0080]    Next, a method of manufacturing a first lead-out wiring region including the gate wiring of the semiconductor device described in this embodiment will be explained by FIG. 2 to FIG. 7.  
         [0081]    Thermal diffusion is performed, for example, by selectively ion-implanting an N-type impurity in the surface of a P-type base region  202  formed on an N-type semiconductor substrate  201  to thereby form an N-type source region (not shown) in a predetermined region of the cell forming region. Then, as shown in FIG. 2, a first insulating film  203  is formed on the P-type base region  202 . A first gate wiring  204  is formed using a conductive material such as polysilicon on part of the first insulating film  203 . The first gate wiring  204  is connected to a trench gate electrode (not shown) formed in the cell forming region such as a trench MOSFET. A first interlayer dielectric  205  is formed on a side surface and an upper surface of the first gate wiring  204  on the first insulating film  203 .  
         [0082]    Subsequently, a slot portion is formed in the first interlayer dielectric  205  such that the upper surface of the first gate wiring  204  is exposed. Then, a second gate wiring  206  is formed to fill at least the slot portion and electrically connected to the first gate wiring  204 . The second gate wiring  206  is formed of a conductive material such as Al and used as a lead-out wiring. A first source electrode  207  is then formed on the P-type base region  202  and the N-type source region (not shown).  
         [0083]    Thereafter, as shown in FIG. 3, a second insulating film  208  such as a silicon oxide film or a silicon nitride film is formed in such a manner as to cover part of the first source electrode  207  and an upper surface and a side surface of the second gate wiring  206 .  
         [0084]    Then, as shown in FIG. 4, a resist film  209  is applied onto the second insulating film  208  and patterned, so that a pattern of the second insulating film  208  is formed on the second gate wiring  206  and the first interlayer dielectric  205 .  
         [0085]    Subsequently, as shown in FIG. 5, the resist film  209  is ashed, and a second source electrode  210  is formed on an exposed part of the first source electrode  207  and on the second insulating film  208 .  
         [0086]    Next, as shown in FIG. 6, the second source electrode  210  is etched, and a gap  206   a  is formed such that the second insulating film  208  on the second gate wiring  206  and part of the second insulating film  208  on the first source electrode  208  are exposed. An upper surface of the second source electrode  210  is formed higher than the upper surface of the second gate wiring  206 .  
         [0087]    Then, as shown in FIG. 7, a strap  211  is directly connected onto the second source electrode  210 . The connection is made by ultrasonic bonding. The strap  211  is formed of Al, for example.  
         [0088]    [0088]FIG. 8 shows a plan view of the semiconductor device of this embodiment. Here,  801  denotes a semiconductor substrate,  802  denotes a lead frame,  803  denotes a strap,  804  denotes a gate wire, and  805  denotes a gate wiring.  806  denotes an application region of ultrasonic waves. FIG. 9 is a fragmentary sectional view showing an outline of a section taken along the line C-C′ in FIG. 8.  
         [0089]    Since the upper surface of the source electrode is formed higher than the upper surface of the gate wiring as described above, it becomes possible to reduce shock applied to the insulating film formed on the gate wiring when the strap is connected to the source electrode by ultrasonic bonding. Namely, the following situation can be prevented: the gate wiring is crushed and deformed to the source electrode side to thereby cause a short-circuit between the gate wiring and the source electrode; or the insulating film formed on the gate wiring deteriorates to thereby cause a short-circuit between the strap and the gate wiring, and as a result, it becomes possible to eliminate a short-circuit fault without incurring an increase in internal resistance.  
         [0090]    Although the aforementioned second source electrode is formed thicker than the first source electrode on the N-type source region, but it is not limited to this particular example. When the strap is connected onto the second source electrode, more force is applied to the electrode which is formed thicker as a cushioning material to absorb shock. If the first source electrode is formed thicker, the first source electrode functions as a cushioning material when the strap is connected onto the second source electrode. Accordingly, force is applied onto the first source electrode and also to the insulating film on the side wall of the gate wiring, which causes the deterioration of the insulating film. Hence, it is preferable to form the second source electrode thicker since more shock is absorbed by the second source electrode so that the possibility of deterioration of the second insulating film due to shock when the strap is connected is low.  
         [0091]    Moreover, since the second source electrode is formed apart from the gate wiring with a gap therebetween, a short-circuit fault, which is caused because shock is particularly applied to an end portion of the second source electrode when the strap is connected to the upper portion thereof and thereby the second source electrode is deformed, can be prevented.  
         [0092]    Furthermore, the second insulating film needs to be formed so as to cover the gate wiring, but by forming the insulating film to extend onto part of the upper surface of the first source electrode so that an end portion of the first source electrode is covered with the insulating film, a fault caused by misalignment in patterning can be prevented, and in addition, a short-circuit fault caused by deformation when shock is applied to the end portion of the first source electrode when the strap is connected to the upper portion can be prevented.  
         [0093]    In this embodiment, the semiconductor device with an offset mesh trench structure in which a trench is formed in a mesh pattern is described, but without being limited to this, a semiconductor device with a stripe trench structure in which a trench is formed in a striped pattern is also possible.  
         [0094]    (Second Embodiment)  
         [0095]    Next, a semiconductor device of the second embodiment will be explained referring to FIG. 10.  
         [0096]    In this embodiment, the explanation is given with an MOSFET and an IGBT as its examples. FIG. 10 is a fragmentary sectional view of a semiconductor device. As shown in FIG. 10, a first insulating film  1003  is formed, for example, on a P-type base region  1002  of a lead-out wiring region formed on an N-type semiconductor substrate  1001 . A first gate wiring  1004  is formed on the first insulating film  1003 .  
         [0097]    A trench (not shown) is formed perpendicular to the first gate wiring  1004  in the P-type base region  1002  of a cell forming region. The trench has a stripe trench structure. An N-type source region  1005  is selectively formed on the surface of the P-type base region  1002  around the trench. Incidentally, FIG. 10 is a fragmentary sectional view on the N-type source region  1005 . The structure of the cell forming region not shown is the same as that in the aforementioned first embodiment, and hence the explanation thereof is omitted.  
         [0098]    The first gate wiring  1004  is formed of a conductive material such as polysilicon and electrically connected to trench gate electrodes of the cell forming regions in other regions (not shown), respectively. A first interlayer dielectric  1006  such as an UDO or a BPSG is formed on a side surface and part of an upper surface of the first gate wiring  1004 . A second gate wiring  1007  made of a conductive material such as Al is formed on the first gate wiring  1004  on which the first interlayer dielectric  1006  is not formed, and used as a lead-out wiring for the first gate wiring  1004 . The first interlayer dielectric may be integrally formed by an insulating film made of the same material.  
         [0099]    A first source electrode  1008  such as Al is formed on the N-type source region  1005 , and the first source electrode  1008  is formed to be insulated from the first gate wiring  1004  by the first interlayer dielectric  1006 .  
         [0100]    On part of an upper surface of the first source electrode  1008  and a side surface and an upper surface of the second gate wiring  1007 , a second insulating film  1009  is formed to prevent a short-circuit between the second gate wiring  1007  and a strap and a short-circuit between the first source electrode  1008  and the second gate wiring  1007  when the strap is connected by ultrasonic bonding.  
         [0101]    Although the second insulating film  1009  is formed on part of the upper surface of the first source electrode  1008 , it may not be formed thereon. By forming the insulating film to extend onto part of the upper surface of the first source electrode  1008  as described above, a short circuit fault caused by misalignment in patterning can be prevented, whereby a device with high yield and high reliability can be manufactured. The second insulating film  1009  is composed of a silicon oxide film, a silicon nitride film, or a stacked film thereof. It is desirable to use an insulating film with a certain degree of hardness as the second insulating film  1009  since an electrode layer is formed thereon. The thickness of the second insulating film  1009  is preferably 2 μm to 4 μm.  
         [0102]    A second source electrode  1010  such as Al is formed on the first source electrode  1008  and the second insulating film  1009 . The second source electrode  1010  is formed thicker than the first source electrode  1008  on the N-type source region  1005 .  
         [0103]    Deterioration such as deformation in an interface between different kinds of materials and an increase in resistance can be prevented by forming the first source electrode  1008  and the second source electrode  1010  with the same conductive material.  
         [0104]    The second source electrode  1010  is formed also on the second insulating film  1009  formed on the gate wiring  1007 . A strap  1011  which connects with the second source electrode  1010  is formed on the second source electrode  1010 . The strap  1011  is a connecting plate, for example, made of Al. The strap  1011  is connected, for example, to a lead frame (not shown) for connection to the outside.  
         [0105]    As described above, no gap is provided in the second source electrode in this embodiment. Accordingly, it becomes possible to reduce shock applied to the insulating film formed on the gate wiring when the strap is connected to the source electrode by ultrasonic bonding without the addition of steps. Namely, a short-circuit between the gate wiring and the source electrode due to the deformation of the gate wiring can be prevented, whereby it becomes possible to eliminate a short-circuit fault without incurring an increase in internal resistance. Moreover, by forming the area of contact between the source electrode and the strap larger, a reduction in resistance becomes possible.  
         [0106]    Although the aforementioned second source electrode is formed thicker than the first source electrode on the N-type source region, but the present invention is not limited to this particular example. When the strap is connected onto the second source electrode, more force is applied to the electrode which is formed thicker as a cushioning material to absorb shock. If the first source electrode is formed thicker, the first source electrode functions as a cushioning material when the strap is connected onto the second source electrode. Accordingly, force is applied onto the first source electrode and also to the insulating film on the side wall of the gate wiring, which causes the deterioration of the insulating film. Hence, it is preferable to form the second source electrode thicker since more shock is absorbed by the second source electrode so that the possibility of deterioration of the second insulating film due to shock when the strap is connected is low.  
         [0107]    Furthermore, the second insulating film needs to be formed so as to cover the gate wiring, but by forming the insulating film to extend onto part of the upper surface of the first source electrode so that an end portion of the first source electrode is covered with the insulating film, a fault caused by misalignment in patterning can be prevented, and in addition, a short-circuit fault caused by deformation when shock is applied to the end portion of the first source electrode when the strap is connected to the upper portion can be prevented.  
         [0108]    In this embodiment, the semiconductor device with a stripe trench structure in which a trench is formed in a striped pattern is described, but without being limited to this, a semiconductor device with an offset mesh trench structure in which a trench is formed in a mesh pattern is also possible.  
         [0109]    (Third Embodiment)  
         [0110]    A semiconductor device of the third embodiment will be explained referring to FIG. 11 to FIG. 19.  
         [0111]    In this embodiment, the explanation is given with an MOSFET and an IGBT as its examples. FIG. 11 is a sectional view taken along the line A-A′-B-B′ in FIG. 16. A first and second lead-out wiring regions and a cell forming region are shown. The first lead-out wiring region is a lead-out wiring region sandwiched between the cell forming regions, and the second lead-out wiring region is a lead-out wiring region formed in at least part of an outer peripheral region of the cell forming region.  
         [0112]    As shown in FIG. 11, a P-type base region  1102  is formed, for example, on an N-type semiconductor substrate  1101  of the first lead-out wiring region and the cell forming region. First insulating films  1103   a  and  1103   b  are formed on the P-type base region  1102  of the first and second lead-out wiring regions and on the semiconductor substrate  1101 . First gate wirings  1104   a  and  1104   b  are formed on the first insulating films  1103   a  and  1103   b , respectively.  
         [0113]    In the P-type base region  1102  of the cell forming region, a trench  1105  is formed perpendicular and parallel to the first gate wiring  1104   a  in the first lead-out wiring region. The trench  1105  has an offset mesh trench structure. Incidentally, FIG. 11 is a fragmentary sectional view of a region in which the trench  1105  is formed perpendicular to the first gate wiring  1104   a  in the first lead-out wiring region. A gate insulating film  1106  is formed in the trench  1105 , and a trench gate electrode  1107  is buried in the trench  1105  in such a manner as to touch the gate insulating film  1106 . An N-type source region  1108  is formed on the surface of the P-type base region  1102  around the trench  1105  The N-type source region  1108  is not formed around the trench  1105  on the first lead-out wiring region side.  
         [0114]    A cell formed in the cell forming region functions as a MOSFET if an N + -type drain region is formed under the semiconductor substrate  1101  and a drain electrode is formed so as to touch the N + -type drain region, and functions as an IGBT (Insulated Gate Bipolar Transistor) if a P + -type collector region is formed under the semiconductor substrate  1101  and a collector electrode is formed so as to touch the P + -type collector region. The cell formed in the cell forming region is not limited to the above. The structure of the cell is not limited to a trench type, and may be a planer type.  
         [0115]    The first gate wirings  1104   a  and  1104   b  and the trench gate electrode  1107  are formed of a conductive material such as polysilicon and electrically connected to each other in another region (not shown).  
         [0116]    First interlayer dielectrics  1109   a  and  1109   b  such as a UDO (Undoped Oxide) or a BPSG are formed on side surfaces and part of each of upper surfaces of the first gate wirings  1004   a  and  1104   b  of the first and second lead-out wiring regions, respectively. The first insulating films and the first interlayer dielectrics may be formed integrally by an insulating film made of the same material. On the first gate wirings  1104   a  and  1104   b  on which the first interlayer dielectrics  1109   a  and  1109   b  are not formed, second gate wirings  1110   a  and  1110   b  made of a conductive material such as Al are formed and used as lead-out wirings. A second interlayer dielectric  1111  is formed on the trench electrode  1107 . The second interlayer dielectric  1111  may be completely buried in the trench  1105 .  
         [0117]    A first source electrode  1112  such as Al is formed on the P-type base region  1102  and the N-type source region  1108  of the cell forming region. The first source electrode  1112  is formed so as to have a large area, which leads to a reduction in resistance. The first source electrode  1112  is formed to be insulated from the first gate wirings  1104   a  and  1104   b  and the trench gate electrode  1107  by the first interlayer dielectrics  1109   a  and  1109   b  and the second interlayer dielectric  1111 . Second insulating films  1113   a  and  1113   b  whose ends are formed on part of an upper surface of the first source electrode  1112  are formed on side surfaces and upper surfaces of the second gate wirings  1110   a  and  1110   b , respectively. The second insulating film  1113   a  formed in the first lead-out wiring region is formed in order to, when an almost platy connecting plate (here called a strap) is connected to the upper portion thereof by ultrasonic bonding, prevent a short-circuit between the second gate wiring  1110   a  and the strap and a short-circuit between the first source electrode  1112  and the second gate wiring  1110   a.    
         [0118]    Although the second insulating films  1113   a  and  1113   b  are formed on part of the upper surface of the first source electrode  1112 , they may not be formed thereon. However, by forming the insulating films to extend onto part of the upper surface of the first source electrode  1112  as described above, a short circuit fault caused by misalignment in patterning can be prevented, whereby a device with high yield and high reliability can be manufactured. The second insulating films  1113   a  and  1113   b  are composed of a silicon oxide film, a silicon nitride film, or a stacked film thereof. It is desirable to use an insulating film with a certain degree of hardness as the second insulating films  1113   a  and  1113   b  since an electrode layer is formed thereon. The thickness of the second insulating films  1113   a  and  1113   b  is preferably 2 μm to 4 μm.  
         [0119]    A second source electrode  1114  such as Al is formed on the first source electrode  1112  in the cell forming region and on part of each of the second insulating films  1113   a  and  1113   b  which are formed on the first source electrode  112 . An upper surface of the second source electrode  1114  is formed higher than upper surfaces of the second gate wirings  1110   a  and  1110   b . The second gate wiring  1110   a  and the second source electrode  1114  in the first lead-out wiring region are arranged with a gap  1110   c  between them. The second source electrode  1114  is formed thicker than the first source electrode  1112  on the N-type source region  1108 . Moreover, a gate electrode  1115  such as Al is formed on the second gate wiring  1110   b  in the second lead-out wiring region and on the second insulating film  1113   b  formed on the first source electrode  1112 . The second source electrode and the gate electrode  1115  are formed apart from each other.  
         [0120]    Deterioration such as deformation in an interface between different kinds of materials and an increase in resistance can be prevented by forming the first source electrode  1112  and the second source electrode  1114  with the same conductive material.  
         [0121]    A strap  1116   a  which connects with the second source electrode  1114  is formed on the second source electrode  1114 . The strap  1116   a  is a connecting plate, for example, made of Al. The strap  1116   a  is connected to a lead frame (not shown), for example, for connection to the outside. A strap  1116   b  which connects with the gate electrode  1115  is formed on the gate electrode  1115 . The strap  1116   b  is connected to the lead frame (not shown), for example, for connection to the outside. In a surface region of an outer peripheral edge of the second lead-out wiring region, an N-type stopper region  1117  is formed to prevent the extension of a depletion layer when a reverse bias is applied.  
         [0122]    The example in which the strap  1116   b  as the connecting plate is connected to the gate electrode  1115  is described here, but, without being limited to this example, as shown in the first embodiment, connection by a gate wire is also possible.  
         [0123]    Next, a method of manufacturing the first and second lead-out wiring regions including gate wirings of the semiconductor device shown in FIG. 11 which is described in this embodiment will be explained by FIG. 12 to FIG. 15. The cell forming region, part of which is omitted, will be described.  
         [0124]    As shown in FIG. 12, a P-type base region  1202  is formed on a semiconductor substrate  1201  in the first lead-out wiring region. Subsequently, first insulating films  1203   a  and  1203   b  are formed on the P-type base region  1202  in the first and second lead-out wiring regions and on the semiconductor substrate  1201 . Polysilicon is deposited on the first insulating films  1203   a  and  1203   b  and etched to form first gate wirings  1204   a  and  1204   b  on part of each of the first insulating films  1203   a  and  1203   b  in the first and second lead-out wiring regions. Silicon nitride films are formed on upper surfaces and side surfaces of the first gate wirings  1204   a  and  1204   b  and etched to form slot portions such that part of each of the upper surfaces of the first gate wirings  1204   a  and  1204   b  is exposed, and thus interlayer dielectrics  1205   a  and  1205   b  are formed.  
         [0125]    In the cell forming region, a cell at least composed of a gate insulating film  1206 , a trench gate electrode  1207 , an N-type source region  1208 , and a second interlayer dielectric  1209  is formed. Then, Al is deposited and etched to form second gate wirings  1210   a  and  1210   b  in the first and second lead-out wiring regions, respectively, and a first source electrode  1211  is formed in the cell forming region. An N-type stopper region  1212  is formed in a surface region of an outer peripheral edge of the second lead-out wiring region.  
         [0126]    Thereafter, as shown in FIG. 13, a second insulating film  1213  such as a silicon oxide film or a silicon nitride film is deposited in the first and second lead-out wiring regions.  
         [0127]    Then, as shown in FIG. 14, by applying a resist film and forming a resist pattern, a second insulating film  1213   a  such as covers the second gate wiring  1210   a  and a second insulating film  1213   b  such that part of an upper surface of the second gate wiring  1210   b  is exposed are formed. The resist pattern is removed by ashing. End portions of the second insulating films  1213   a  and  1213   b  are formed to extend onto the first source electrode  1211 .  
         [0128]    Next, as shown in FIG. 15, by depositing Al, applying a resist film onto the Al, and forming a resist pattern, a second source electrode  1214  is formed on the first source electrode  1211  and on the insulating films  1213   a  and  1213   b  on the first source electrode  1211 . A gate electrode  1215  is formed on the second wiring  1210   b  and the second insulating film  1213   b  formed in the second lead-out wiring region. An end portion of the gate electrode  1215  is formed to extend onto the second insulating film  1213   b  formed on the first source electrode  1211 .  
         [0129]    The second insulating film  1213   b  is formed so that part of an upper surface of the second gate wiring  1210   b  is exposed, and out of the second insulating film  1213   b , a portion which is formed on the opposite side of the second insulating film extending onto the first source may be a film with a lower hardness than a silicon nitride film and a silicon oxide film and hence may be formed of polyimide used as a protective film since it is unnecessary to form an electrode thereon. Subsequently, a strap  1216   a  is formed on the cell forming region and the first lead-out wiring region by ultrasonic bonding, while a strap  1216   b  is formed on the gate electrode formed in the second lead-out wiring region by ultrasonic bonding and connected to the lead frame (not shown).  
         [0130]    [0130]FIG. 16 shows a plan view of the semiconductor device of this embodiment. Here,  1601  denotes a semiconductor substrate,  1602  denotes a lead frame,  1603  denotes a strap,  1604   a  denotes a gate wiring in the first lead-out wiring region, and  1604   b  denotes a gate wiring in the second lead-out wiring region.  1605  denotes an application region of ultrasonic waves. A fragmentary sectional view showing an outline of a section taken along the line C-C′ in FIG. 16 is the same as FIG. 9 shown in the first embodiment.  
         [0131]    Since an upper surface of the second source electrode is formed higher than or on about the same level with an upper surface of the insulating film on the gate wiring as described above, it becomes possible to reduce shock applied to the insulating film formed on the gate wiring when the strap is connected to the source electrode by ultrasonic bonding. Namely, the following situation can be prevented: the gate wiring is crushed and deformed to the source electrode side to thereby cause a short-circuit between the gate wiring and the source electrode; or the insulating film formed on the gate wiring deteriorates to thereby cause a short-circuit between the strap and the gate wiring, whereby it becomes possible to eliminate a short-circuit fault without incurring an increase in internal resistance.  
         [0132]    Although the aforementioned second source electrode is formed thicker than the first source electrode on the N-type source region, but the present invention is not limited to this particular example. When the strap is connected onto the second source electrode, more force is applied to the electrode which is formed thicker as a cushioning material to absorb shock. If the first source electrode is formed thicker, the first source electrode functions as a cushioning material when the strap is connected onto the second source electrode. Accordingly, force is applied onto the first source electrode and also to the insulating film on the side wall of the gate wiring, which causes the deterioration of the insulating film. Hence, it is preferable to form the second source electrode thicker since more shock is absorbed by the second source electrode so that the possibility of deterioration of the second insulating film due to shock when the strap is connected is low.  
         [0133]    Moreover, since the second source electrode is formed apart from the gate wiring with a gap therebetween, a short-circuit fault, which is caused because shock is particularly applied to an end portion of the second source electrode when the strap is connected to the upper portion thereof and thereby the second source electrode is deformed, can be prevented.  
         [0134]    Furthermore, although the second insulating film formed in the first lead-out wiring region is formed to extend onto part of the upper surface of the first source electrode, the second insulating film has only to be formed so as to cover the second gate wiring. However, by forming the second insulating film to extend onto part of the upper surface of the first source electrode so that an end portion of the first source electrode is covered with the second insulating film, a fault caused by misalignment in patterning can be prevented, and in addition, a short-circuit fault caused by deformation when shock is applied to the end portion of the first source electrode when the strap is connected to the upper portion can be prevented.  
         [0135]    Moreover, in a related art, as shown in FIG. 25, a second lead-out wiring region which is formed in the same process as a first lead-out wiring region is formed side by side with a cell forming region, and no cell such as a MOSFET is formed under the second lead-out wiring region. As shown in FIG. 26A and FIG. 26B, in semiconductor chips corresponding to packages having symmetrical structures, the positions of respective gate electrodes  2602  on respective semiconductor chips  2601  are different even in the packages of the same size, whereby there is a problem that the semiconductor chips  2601  to be mounted need to be designed individually. Here in FIG. 26A and FIG. 26B, 2603 denotes a source electrode, and  2604  denotes a gate wiring.  
         [0136]    Besides, there is a problem that when, in order to reduce on-state resistance, the area of the cell forming region of the semiconductor chip is formed wider, the number of cells is increased, and the area of the source electrode is formed more widely, the area, number, position, shape, and so on of gate electrodes are limited. Further, there is a problem that it is necessary to select the area, number, position, shape, and so on of gate electrodes depending on the position of a lead frame.  
         [0137]    In this embodiment, in the second lead-out wiring region, the second insulating film is formed between the gate electrode and the first source electrode, and they are insulated. Hence, the cell forming region can be provided under part of the second lead-out wiring region, whereby regardless of the area of the gate electrode, the area of the cell forming region can be formed more widely, resulting in a reduction in on-state resistance. Moreover, regardless of the area of the cell forming region and the position of the lead frame, the area, number, position, shape, and so on of gate electrodes can be selected. Namely, desired area, number, position, shape, and so on of gate electrodes can be selected, and in addition, the area of the cell forming region can be formed more widely, leading to a reduction in on-state resistance.  
         [0138]    Furthermore, concurrently with the formation of the wider cell forming region, the gate electrodes can be formed in two corner portions of the semiconductor chip as shown in FIG. 17, and hence new designing is unnecessary even in semiconductor chips (for example, in FIG. 26A and FIG. 26B) in which the positions of gate electrodes are different corresponding to packages.  1701  denotes a semiconductor chip,  1702  denotes a gate electrode,  1703  denotes a source electrode, and  1704  denotes a gate wiring.  
         [0139]    Moreover, by forming the gate electrode in a region parallel to a long side or a short side of the semiconductor chip as shown in FIG. 18A and FIG. 18B, it is possible not only to form the cell forming region widely but also to form the gate electrode optionally widely. Thanks to this formation, the strap structure can be formed more easily, and besides a reduction in resistance becomes possible. Further, since the connection between the gate electrode and the lead frame can be performed at an optional position, the semiconductor device with a high degree of flexibility in position, size, and so on can be formed.  
         [0140]    The second insulating film in the first lead-out wiring region and the second insulating film in the second lead-out wiring region can be formed in the same process. Also, the second source electrode in the cell forming region and the gate electrode in the second lead-out wiring region can be formed in the same process.  
         [0141]    Although the semiconductor device with an offset mesh trench structure in which a trench is formed in a mesh pattern is described in this embodiment, the present invention is not limited to this example, and a semiconductor device with a stripe trench structure in which a trench is formed in a striped pattern is also possible. Moreover, although, in this embodiment, as the structure of the first lead-out wiring region, the first embodiment (FIG. 1) in which the source electrode is not formed on the second gate wiring is used as shown in FIG. 11, the second embodiment (FIG. 10) in which the source electrode is formed on the second gate wiring as shown in FIG. 19 can be also used.  
         [0142]    In the aforementioned first to third embodiments, a fault due to shock caused when the strap is bonded by ultrasonic bonding is described, but the present invention is not limited to this and has also a sufficient effect on shock caused by pressure welding bonding.  
         [0143]    Moreover, the example in which the source electrode is composed of a double-layer electrode layer is described, but it may be composed of a one-layer electrode layer or a three or more layer electrode. Further, although the case where the source electrode is formed on the source region is explained, the source electrode may be a drain electrode, an emitter electrode, a collector electrode, or the like depending on the structure of a cell formed in the cell forming region.