Abstract:
A semiconductor device provides an element arrangement region on a semiconductor substrate including: a first semiconductor region on the semiconductor substrate; a second semiconductor region on the first semiconductor region; multiple trench gates penetrating the first semiconductor region and reaching the second semiconductor region; a third semiconductor region contacting the trench gate; a fourth semiconductor region on a rear surface; a first electrode connected to the first and second semiconductor regions; and a second electrode connected to the fourth semiconductor region. Each trench gate includes a main trench gate for generating a channel and a dummy trench gate for improving a withstand voltage of a component. The device further includes: a dummy gate wiring for applying a predetermined voltage to the dummy trench gate; and a dummy pad connected to the dummy gate wiring. The dummy pad and the first electrode are connected by a conductive member.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on Japanese Patent Application No. 2014-146275 filed on Jul. 16, 2014, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a semiconductor device including an insulated gate bipolar transistor having a dummy trench gate, and a manufacturing method for the semiconductor device. 
     BACKGROUND 
     It has been known that a trench gate is arranged for improving the withstand voltage of an insulated gate bipolar transistor (IGBT). The testing of withstand voltage of an insulated film or measurement of a margin at a dummy trench gate is performed by applying a predetermined potential between a gate electrode and an emitter electrode of the dummy trench gate as disclosed in Patent Document 1. 
     However, it is common that the gate electrode is connected to the emitter electrode during manufacturing an element and the dummy gate trench is fixed to have the same potential as the emitter potential of the IGBT. Accordingly, the testing of withstand voltage for the dummy trench gate cannot be operated after completing the formation of the upper layer (i.e., the outer portion of the surface of a semiconductor substrate) of the IGBT. 
     Since the distributions of electrical field in a variety of elements for constituting an IGBT are different in the process of forming the upper layer and the completion of forming the upper layer, it is possible that the withstand voltage cannot be accurately measured in a conventional method. 
     [Patent Document 1] Japanese Patent Application Publication No. 2013-251466 
     SUMMARY 
     It is an object of the present disclosure to provide a semiconductor device that conducts a withstand voltage testing for a dummy trench gate accurately. In addition, the present disclosure also provides a manufacturing method for the semiconductor device. 
     A first aspect of the present disclosure relates to a semiconductor device. The semiconductor device provides an element arrangement region arranged at a main surface side of the semiconductor substrate that includes: a first semiconductor region that is arranged in a surface portion of the semiconductor substrate at the main surface side; a second semiconductor region that contacts the first semiconductor region and is arranged at a position deeper than the first semiconductor region; a plurality of trench gates that penetrate the first semiconductor region and reach the second semiconductor region; a third semiconductor region that is arranged in the first semiconductor region to be in contact with each of the plurality of trench gates; a fourth semiconductor region that is arranged in a surface portion of the semiconductor substrate at a rear surface side opposite to the main surface side; a first electrode that is arranged on a main surface and electrically connected to the first semiconductor region and the second semiconductor region; and a second electrode that is arranged on a rear surface and electrically connected to the fourth semiconductor region. Each of the plurality of trench gates includes a main trench gate for generating a channel by voltage application and a dummy trench gate without contribution to generating a channel for improving a withstand voltage of the semiconductor device. The semiconductor device further includes: a dummy gate wiring that is arranged on the main surface of the semiconductor substrate for applying a predetermined voltage to the dummy trench gate; and a dummy pad that is connected electrically to the dummy gate wiring. The dummy pad and the first electrode are mutually connected electrically through a conductive member at the main surface side of the semiconductor substrate. 
     A second aspect of the present disclosure relates to a manufacturing method of a semiconductor device providing an element arrangement region at a main surface side of a semiconductor substrate including: a first semiconductor region that is arranged in a surface portion of the semiconductor substrate at the main surface side; a second semiconductor region that contacts the first semiconductor region and is arranged at a position deeper than the first semiconductor region; a plurality of trench gates that penetrate the first semiconductor region and reach the second semiconductor region; a third semiconductor region that is arranged in the first semiconductor region to be in contact with each of the plurality of trench gates; a fourth semiconductor region that is arranged in a surface portion of the semiconductor substrate at a rear surface side opposite to the main surface side; a first electrode that is arranged on a main surface and electrically connected to the first semiconductor region and the second semiconductor region; and a second electrode that is arranged on a rear surface and electrically connected to the fourth semiconductor region, in which each of the plurality of trench gates includes a main trench gate for generating a channel by voltage application and a dummy trench gate without contribution to generating a channel for improving a withstand voltage of a component. The method includes: forming the first semiconductor region, the second semiconductor region, the third semiconductor region and the fourth semiconductor region in the semiconductor substrate; forming the plurality of trench gates in the surface portion of the semiconductor substrate at the main surface side subsequent to the forming of the first semiconductor region, the second semiconductor region, the third semiconductor region and the fourth semiconductor region; forming a dummy gate wiring connected to the dummy trench gate as a part of each of the plurality of trench gates for applying a predetermined voltage to a gate electrode of the dummy trench gate subsequent to the forming of the plurality of trench gates; forming a dummy pad electrically connected to the dummy gate wiring to be in contact with a probe for a withstand voltage testing subsequent to the forming of the dummy gate wiring; forming the first electrode on the main surface of the semiconductor substrate subsequent to the forming of the dummy gate wiring; performing a withstand voltage testing by bringing the probe into contact with the dummy pad and the first electrode respectively subsequent to the forming the dummy pad and the first electrode; and electrically connecting the dummy pad and the first electrode mutually so as to have a same potential level subsequent to the performing of the withstand voltage testing. 
     According to the first and second aspects of the present disclosure, the dummy pad and the first electrode are mutually connected electrically by the conductive member at the main surface side of the semiconductor substrate. In other words, the dummy pad and the first electrode are arranged to be exposed at the upper layer above the main surface of the semiconductor substrate prior to the electrical connection. Accordingly, it is possible to apply a predetermined voltage between the dummy pad and the first electrode by bringing the probe into contact with the dummy pad and the first electrode from outside prior to making the electrical connection mutually. That is, it is possible to conduct a withstand voltage testing for the dummy trench gate when the upper layer is nearly finished. Therefore, it is possible to obtain the result of a withstand voltage testing accurately as compared to the conventional method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a diagram that shows the overview configuration of a semiconductor device according to a first embodiment, and  FIG. 1  is a cross-sectional view taken along line I-I of  FIG. 2 ; 
         FIG. 2  is a diagram that shows a front view of the overview configuration of the semiconductor device, and it is noted that an emitter electrode is indicated by a broken line; 
         FIG. 3  is a diagram that shows a cross-sectional view of the formation of an element; 
         FIG. 4  is a diagram that shows a cross-sectional view of the formation of a trench gate; 
         FIG. 5  is a diagram that shows a cross-sectional view of a dummy trench gate wiring formation process; 
         FIG. 6  is a diagram that shows a cross-sectional view of a dummy pad formation process and a first electrode formation process; 
         FIG. 7  is a diagram that shows a process of forming a plating layer and passivation film; 
         FIG. 8  is a diagram that shows a withstand voltage testing process; 
         FIG. 9  is a diagram that shows a cross-sectional view of forming a lower layer; 
         FIG. 10  is a diagram that shows the overview configuration of a semiconductor device according to a second embodiment, and  FIG. 10  is also a diagram that shows a cross sectional view taken along line X-X of  FIG. 11 ; 
         FIG. 11  is a diagram that shows a front view of the overall configuration of the semiconductor device, and it is noted that an emitter electrode and a lead frame at the side of the emitter are indicated by a broken line and a two-dot chain line respectively; and 
         FIG. 12  is a diagram that shows a front view of the overall configuration of a semiconductor device according to a modification example, and it is noted that an emitter electrode and a lead frame at the side of the emitter are indicated by a broken line and a two-dot chain line respectively. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes the embodiments of the present disclosure based on the drawings. It is noted that an x-direction, a y-direction perpendicular to the x-direction, and a z-direction linearly independent of the x-direction and the y-direction are defined in each diagram. 
     (First Embodiment) 
     The overall configuration of a semiconductor device according to the present embodiment is described with reference to  FIG. 1  and  FIG. 2 . 
     The semiconductor device includes, for example, an insulated bipolar transistor (hereinafter referred to as IGBT). The semiconductor device mentioned below is a transistor having a trench-type gate in particular. 
     As shown in  FIG. 1 , the semiconductor device  100  is configured by a semiconductor substrate  10 , an upper layer  20  and a lower layer  30  of the semiconductor substrate  10 . A base region  11  as a first semiconductor region, an emitter region  12  as a third semiconductor region, a drift region  13  as a second semiconductor region, and a collector region  14  as a fourth semiconductor region are formed on the semiconductor substrate  10 . Moreover, a trench gate  15  is formed on the semiconductor substrate  10 . 
     An upper layer  20  formed above a main surface  10   a  of the semiconductor substrate  10  includes a dummy gate wiring  21 , a dummy pad  22 , and an emitter electrode  23  as a first electrode. Moreover, a plating layer  24 , a soldering layer  25 , and a bonding wire  26  as a conductive member are formed in the present embodiment. 
     A lower layer  30  formed at the side of a rear surface  10   b  opposite to the main surface  10   a  includes a collector layer  31  as a second electrode, a soldering layer  32 , and a collector-side lead frame  33  as a second lead frame. 
     The following describes each of the configuration elements in detail. 
     Initially, a variety of elements formed on the semiconductor substrate  10  are described. As shown in  FIG. 1 , the n-type drift region  13  is laminated on the surface of the p-type collector region  14  having a predetermined thickness in a z-direction (corresponding to a thickness direction). Then, the p-type base region  11  is laminated on the surface of the drift region  13 . The surface of the base region  11  that is opposite to the drift region  13  is the main surface  10   a  of the semiconductor substrate  10 . The trench gate  15  is formed so as to extend in the z-direction from the main surface  10   a  of the semiconductor substrate  10  and penetrate the base region  15  and lead to the drift region  13 . The trench gate  15  includes a gate electrode  16  made of, for example, polysilicon inside, and an insulation film  17  for separating the gate electrode  16  and each of the semiconductor regions. The insulation film is, for example, an oxide film that projects toward the main surface  10   a  at the side of the upper layer  20 . 
     A plurality of trench gates  15  are formed in the x-direction as shown in  FIG. 1 . The trench gate  15  includes: a main trench gate  15   a  that functions as a channel in the base region upon voltage application; and a dummy trench  15   b  that does not form a channel even if having voltage application. The n-type emitter region  12  is formed on a portion having a contact with the main trench  15   a , which is the surface layer of the semiconductor substrate  10  at the side of the main surface  10   a . In addition, a p-type base collector region  18  having concentration higher than the base region  11  is formed on the outermost surface layer of the base region  11 . 
     In addition, each of the trenches  15  is extended in a y-direction as shown in  FIG. 2 . It is noted that the present embodiment shows an example in which three main trenches  15   a  and three dummy trenches  15   b  are lined up alternatively so as to be in one group; however, it is not restricted to the above pattern. In addition,  FIG. 2  is a frontal view; however, hatching is conducted on a portion relevant to the dummy trench  15   b  for simplicity. 
     Next, each of the elements formed on the upper layer  20  is described. As shown in  FIG. 1 , the dummy gate wiring  21  are formed so as to make an electrical contact with the gate electrode  16  of the dummy trench gate  15   b . In  FIG. 1 , the dummy gate wiring  21  is illustrated only at the rightmost edge of the dummy trench gate  15   b ; however, each of the dummy trench gates  15   b  is interconnected by the dummy gate wiring  21  at the edge part in the y-direction as shown in  FIG. 2 . Then, the dummy pad  22  is formed by electrically connecting to the gate electrode  16  of the dummy trench gate  15   b  through the dummy gate wiring  21 . Moreover, the emitter electrode  23  is formed as a laminated first electrode so as to making contact with the main surface  10   a  of the semiconductor substrate  10 . The processes of forming the dummy pad  22  and the emitter electrode  23  according to the present embodiment are conducted simultaneously, and the heights in the z-direction are set to be the same. More specifically, the main surface  10   a  of the semiconductor substrate  10  is set to have the height that is identical to the heights of one surface  22   a  and one surface  23   a  respectively located at the opposite side. The dummy pad  22  and the emitter electrode  23  are spaced from each other by the insulation film  17  and the passivation film  27  in the x-direction. 
     On the other hand, the plating layer  24  in the z-direction is laminated on the dummy pad  22  and the emitter electrode  23 , and the soldering layer  25  is further laminated on the plating layer  24 . The soldering layer  25  is not formed on the passivation film  27 . The soldering layer  25  includes: a soldering layer having a conductive state with the dummy pad  22 ; and a soldering layer  25   b  having a conductive state with the emitter electrode  23 , and these layers are separated to each other. Then, in the present embodiment, the bonding wire  26  is linked between the soldering layer  25   a  and the soldering layer  25   b , and the both layers are electrically connected to each other. As a result, the potential of the emitter electrode  23  and the potential of the gate electrode  16  of the dummy trench gate  15   b  are identical. 
     As shown in  FIG. 2 , the semiconductor device  100  includes a main gate pad  28  for applying a predetermined voltage to the main trench gate  15   a , and the main trench pad  28  is connected to the gate electrode  16  of each of the main trench gates  15   a  through a main gate wiring  29 . That is, at the time of driving the IGBT, a gate potential corresponding to an ON/OFF state of the IGBT is applied to the main gate pad  28  and a channel is formed in the base region near the trench gate  15   a . However, the dummy trench gate  15   b  is at a potential level (typically at a GND level) identical to the potential of the emitter electrode  23 . 
     The element formation region refers to a region inside the outer edge of the emitter electrode  23  as indicated by the broken line in  FIG. 2 . The dummy pad  22  according to the present embodiment is formed outside the element formation region when it is viewed from the semiconductor substrate  10  in the thickness direction, that is, the z-direction. 
     Next, the elements formed on the lower layer  30  are described. As shown in  FIG. 1 , a collector electrode  31  is formed to make a contact of the collector region  14  of the rear surface  10   b  opposite to the main surface  10   a  of the semiconductor substrate  10 . In addition, the collector electrode  31  is electrically connected to the collector-side lead frame  33  through the soldering layer  32 . The collector-side lead frame  33  is a part where a predetermined voltage is applied when driving the IGBT. That is, it is possible to provide a predetermined potential to the collector region  14  by placing the semiconductor substrate  10  on the collector-side lead frame  33  through the soldering layer  32 . 
     Next, the manufacturing method for the semiconductor device  100  according to the present embodiment is described with reference to  FIG. 1  and  FIGS. 3 to 9 . 
     Initially, the element formation process is operated as shown in  FIG. 3 . The element formation process is a process for forming a part corresponding to the semiconductor substrate  10 . In this process, ions as impurity are injected into a silicon wafer, and the base region  11 , the emitter region  12 , the drift region  13 , the collector region  14  and the base-contact region  18  are formed through activation and diffusion through annealing. The emitter region  12  is formed at a location corresponding to the after-mentioned main trench gate  15   a . Since this process complies with the well-known manufacturing method for an IGBT, the following does not describe the detailed description. 
     Next, as shown in  FIG. 4 , the trench gate formation process is carried out for forming the trench gate  15 . In this process, a trench is formed by dry etching, particularly plasma etching. Then, the insulation film  17  is covered by the trench inner wall through CVD. The insulation film  17  according to the present embodiment is a silicon oxide film. Moreover, the gate electrode  16  made of poly-silicon is buried into the trench. Then, the insulation film  17  is coated on the gate electrode  16  and the trench gate  15  is formed so that the emitter electrode  23 , which is formed later, and the gate electrode  16  are not conductive to each other. The trench gate  15 , with which the emitter region  12  has contact, corresponds to the main trench gate  15   a , and the trench gate  15  excluding the main trench gate  15   a  corresponds to the dummy trench gate  15   b.    
     Next, as shown in  FIG. 5 , the dummy gate wiring formation process is carried out. This process forms the dummy gate wiring  21  for applying a predetermined potential to the gate electrode  16  of the dummy trench gate  15   b . The dummy gate wiring  21  is, for example, an aluminum wiring. After the insulation film  17  for covering the gate electrode  16  is peeled off from the dummy trench gate  15   b , aluminum is vaporized through CVD. The dummy gate wiring  21  is formed through the insulation film on the main surface  10   a  of the semiconductor substrate  10 . As described above, the dummy trench gates  15   b  are interconnected to each other at the edge part in the y-direction as shown in  FIG. 2 . 
     Next, as shown in  FIG. 6 , the dummy pad formation process and the first electrode formation process are carried out. It is noted that the first electrode formation process according to the present embodiment is the emitter electrode formation process. In addition, the dummy pad formation process and the first electrode formation process can be carried out simultaneously. Firstly, the insulation film is coated on the dummy gate wiring  21 , and the insulation of the emitter electrode  23  formed in the present process can be ensured. At this time, the entire dummy gate wiring  21  is not covered, and a contact hole  21   a  where one portion of the dummy gate wiring  21  is exposed is formed. Then, aluminum is vaporized by CVD and then the dummy pad  22  and the emitter electrode  23  are formed. The emitter electrode  23  is formed to make a contact with the main surface  10   a  of the semiconductor substrate  10 . In addition, the dummy pad  22  is formed to be insulated from the emitter electrode  23  and to be electrically connected to the dummy gate wiring  21  passing through the contact hole  21   a . It is noted that  FIG. 6  also illustrates the collector electrode formation process for forming the collector electrode  31  on the rear surface  10   b  of the semiconductor substrate  10 . 
     Next, as shown in  FIG. 7 , the process in which plating is provided on the surface of the dummy pad  22  and the emitter electrode  23  is carried out. Initially, the passivation film  27  is formed so as to separate the dummy pad  22  and the emitter electrode  23 . The passivation film  27  is provided to electrically separate the dummy pad  22  and the emitter electrode  23 , and covers a portion of the surfaces of the dummy pad  22  and the emitter electrode  23 . Then, electroless plating is performed on the portion where the dummy pad  22  and the emitter electrode  23  is not covered by the passivation film  27  and then the plating layer  24  is formed. It is noted that the reference numeral of the plating layer  24  formed on the dummy pad  22  is designated as  24   a , and the reference numeral of the plating layer  24  formed on the emitter electrode  23  is designated as  24   b.    
     The formation is complete for the region of the semiconductor substrate  10  in each process up to the present process. The structure does not change in the later processes. It is noted that the gate electrode  16  of the main trench gate  15   a  and the gate electrode  16  of the dummy trench gate  15   b  are insulated. 
     Next, as shown in  FIG. 8 , the withstand voltage testing process is carried out. The withstand voltage testing process is a process that examines the withstand voltage of the insulation film  17  of the dummy trench gate  15   b . A separate testing probe  40  for testing a withstand voltage comes into contact with the plating layer  24   a  and the plating layer  24   b  respectively. Then, a potential difference required for testing is generated between the testing probe  40   a  coming into contact with the plating layer  24   a  and the testing probe  40   b  coming into contact with the plating layer  24   b . The generation pattern for a potential difference is arbitrary depending on the type of testing such as applying a potential to a pulse shape or applying a potential for a predetermined time. Since the insulation is tested between the dummy pad  22  and the emitter electrode  23 , the tester for examining insulation can also be used. 
     Next, as shown in  FIG. 9 , the collector-side lead frame  33  and the collector electrode  31  are electrically connected through the soldering layer  32  so that the collector  31  and the collector-side lead frame  33  is in opposite. 
     Finally, an electrical connection process is carried out. The electrical connection process according to the present embodiment is a bonding process that makes the dummy pad  22  and the emitter electrode  23  electrically connected through the bonding wire  26  at the same potential level. In this process, the soldering layers  25   a ,  25   b  are respectively formed on the parts corresponding to the plating layers  24   a ,  24   b . Then, the soldering layer  25   a  and the soldering layer  25   b  are connected by the bonding wire  26  and both of the soldering layers  25   a ,  25   b  are electrically connected. Thus, the semiconductor device  100  illustrated in  FIG. 1  is formed. 
     Next, the functional effect of the semiconductor device  100  according to the present embodiment is described. 
     With regard to the semiconductor device  100 , the formation of the regions of the semiconductor substrate  10  is complete in all processes prior to the withstand voltage testing process, and the structure does not change in the processes subsequent to the withstand voltage testing process. The gate electrode  16  of the main trench gate  15   a  and the gate electrode  16  of the dummy trench gate  15   b  are electrically insulated prior to the withstand voltage testing process. The dummy pad  22  and the emitter electrode  23  are formed to be exposed to the side of the upper layer  20  relative to the main surface  10   a  of the semiconductor substrate  10  in the early stage of the electrical connection process as the process in which both of the dummy pad  22  and the emitter electrode  23  are connected electrically. Alternatively, the plating layer  24  electrically connected to the dummy pad  22  and the emitter electrode  23  is formed to be exposed to the upper layer  20  relative to the main surface  10   a  of the semiconductor substrate  10  in the early stage where an electrical connection is mutually made. Accordingly, prior to make an electrical connection mutually, a predetermined potential can be applied to the dummy pad  22  and the emitter electrode  23  by applying the testing probe  40  to the dummy pad  22  and the emitter electrode  23 . In other words, the withstand voltage testing for the insulation film  17  on the dummy trench gate  15   b  can be carried out when the semiconductor substrate  10  and the upper layer  20  are nearly finished. Therefore, the result of testing withstand voltage can be more accurately measured. 
     (Second Embodiment) 
     The first embodiment describes an example in which the dummy pad  22  and the emitter electrode  23  (i.e., first electrode) are electrically connected through the bonding wire  26  as a conductive member. However, the present embodiment describes that the dummy pad  22  and the emitter electrode  23  are connected by an emitter-side lead frame  50  as a first lead frame as shown in  FIG. 10 . 
     A semiconductor device  200  according to the present embodiment includes, for example, the emitter-side lead frame  50  made of copper in replacement of the bonding wire  26  in the semiconductor device  100  according to the first embodiment. 
     The emitter-side lead frame  50  is connected to the emitter electrode  23  through the soldering layer  25   b  and the plating layer  24   b . As shown in  FIG. 10  and  FIG. 11 , the emitter-side lead frame  50  is formed to overlap the emitter electrode  23  when it is viewed from the semiconductor substrate  10  in a thickness direction (i.e., z-direction). In addition, the emitter-side lead frame  50  overlaps the dummy pad  22  when it is viewed from the z-direction, and the emitter-side lead frame  50  and the dummy pad  22  are arranged to face each other. Then, the soldering layer  25   a  and the plating layer  24  are formed in this opposing space, and the emitter-side lead frame  50  and the dummy pad  22  are electrically connected to each other through the soldering layer  25   a  and the plating layer  24 . 
     Since the present embodiment does not use the bonding wire  26  to make an electrical connection with the dummy pad  22  and the emitter electrode  23 , the dummy pad  22  is formed to be smaller than the one in the first embodiment. 
     The following does not describe the configuration elements excluding the emitter-side lead frame  50  that are similar to the one in the first embodiment. 
     The manufacturing method for the semiconductor device  200  according to the present embodiment excluding an electrical connection process is similar to the first embodiment. On the other hand, the electrical connection process according to the present embodiment is a first lead frame formation process that electrically connects the dummy pad  22  and the emitter electrode  23  through the emitter-side lead frame  50  so as to make the dummy pad  22  and the emitter electrode  23  at the same potential level. In this process, the soldering layers  25   a  and  25   b  are initially formed on the parts corresponding to the plating layers  24   a  and  24   b . Then, the emitter-side lead frame  50  is fixed so as to be placed on the upper surfaces of the soldering layers  25   a ,  25   b . The emitter-side lead frame  50  is configured to come into contact with the soldering layer  25   b  corresponding to the emitter electrode  23  and come into contact with the soldering layer  25   a  corresponding to the dummy pad  22  at the same time. Therefore, the semiconductor device  100  illustrated in  FIG. 1  is formed. 
     The functional effect of the semiconductor device  200  according to the present embodiment is described below. 
     For example, the dummy pad  22  described in the first embodiment has to keep a size that is suitable to wire bonding. It is required to make the size larger (i.e., 300 μm to 500 μm) than in a case where the probe for testing withstand voltage is used. As it is not required to use the bonding wire  26  for connection in this embodiment, the size of the dummy pad  22  along an xy-plane can be made smaller in comparison with the configuration having the bonding wire  26 . That is, the layout area of the semiconductor device  200  can be limited. 
     With regard to the configuration which needs the bonding wire  26  such as the first embodiment, since the bonding wire  26 , which is not needed when not testing the withstand voltage of the trench gate, is required for making a connection for the gate electrode and the emitter electrode, the total number of the bonding wire  26  increases and leads to an increase in cost. However, the present embodiment can use the emitter-side lead frame  50  for fixing the emitter electrode  23  at a predetermined potential level, and the emitter-side lead frame  50  can also be used for making an electrical connection between the emitter electrode  23  and the dummy pad  22 . Therefore, the cost in manufacturing the semiconductor device  200  can be limited. 
     Moreover, with regard to the present embodiment, while making an electrical connection between the emitter electrode  23  and the dummy pad  22 , as the emitter-side lead frame  50  moves parallel in a z-direction and comes into contact with the soldering layer  25 , it is possible to make the emitter electrode  23  and the dummy pad  22  to be at the same potential level. In other words, the emitter electrode  23  and the dummy pad  22  can be configured at the same potential level by the so-called self-alignment without the need of controlling the bonding position of the bonding wire  26  correctly. 
     (Modification) 
     In the above first embodiment, since the bonding wire  26  must be used for making connection in the electrical connection process, the dummy pad  22  is arranged in the region inside of the outer edge of the emitter electrode  23  as indicated by the broken line in  FIG. 2 , that is, the outer side of the element formation region. 
     However, in a case where an electrical connection is made between the emitter electrode  23  and the dummy pad  22  with the emitter-side lead frame  50  as described in the second embodiment, the dummy pad  22  can be formed inside of the element formation region. The dummy pad  22  is electrically connected to the dummy gate wiring  21 , and may be arranged to make overlapping of the emitter-side lead frame  50  and the dummy pad  22  when it is viewed from the z-direction. 
     The dummy pad  22  according to the present modification example is formed inside of the outer edge (i.e., the element formation region) of the emitter electrode  23  indicated by the broken line as illustrated in  FIG. 12 . The dummy gate wiring  21  is formed to extend near the center of the element formation region in the x-direction, and the dummy trench gate  15   b  extends to the y-direction from the dummy gate wiring  21 . The main trench gate  15   a  is formed to extend in the y-direction in the region between the adjacent dummy trench gates  15   b  in the x-direction. 
     As described in the present modification example, the area along the xy-plane of the IGBT can be used as the element formation region at the portion excluding the main gate pad  28  by arranging the dummy pad  22  inside the element formation region. 
     (Other Embodiment) 
     The preferred embodiments of the present enclosure are described above; however, the present disclosure is not restricted to the above embodiments. Various modifications and alternations of the present disclosure may be made by those skilled in the art without departing from the scope and spirit of the present disclosure. 
     The above-mentioned embodiments and the modification example illustrate that the withstand voltage testing process is carried out after the formation of the plating layer  24 . However, the testing may be carried out by bringing the testing probe  40  into contact with the plating layer  24  when the dummy pad  22  and the emitter electrode  23  are in an exposed state. 
     The above embodiments and modification examples illustrate that the dummy pad  22  and the emitter electrode  23  are formed to have the identical height in the z-direction; however, it is not restricted to this situation. In fact, it can be ensured that the testing probe  40  comes into contact with the dummy pad  22  and the emitter electrode  23  by setting both to have the identical height in the z-direction. 
     The modification example illustrates the position of the dummy pad  22  is set near the center of the element formation region. However, the formation position of the dummy pad  22  is arbitrary if the dummy pad  22  is electrically connected to the dummy gate wiring  21 , and the emitter-side lead frame  50  and the dummy pad  22  are formed to be overlapped when it is viewed from the z-direction. 
     The above embodiments and the modification example illustrate one example of the configuration material for each element; however, various modifications can be properly made. For example, the dummy pad wiring  21  is illustrated as an aluminum wiring. However, tungsten may also be used. 
     In addition, the above embodiments illustrate an example of a conductivity type in each semiconductor region. However, interchanging of an n-conductivity type and a p-conductivity type may be applicable. 
     The above embodiments and the modification example illustrate an IGBT as an example. However, a MOSFET having the trench gate  15  may be applicable. 
     While the present disclosure has been described with reference to embodiments thereof, it is to be understood that the disclosure is not limited to the embodiments and constructions. The present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.