Patent Publication Number: US-2020295133-A1

Title: Semiconductor device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-047307, filed on Mar. 14, 2019; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a semiconductor device. 
     BACKGROUND 
     A RC-IGBT (Reverse Conducting Insulated Gate Bipolar Transistor) in which a FWD (Free Wheeling Diode) is built into an IGBT (Insulated Gate Bipolar Transistor) is a semiconductor device used in power conversion and the like. It is desirable to develop technology that can suppress breakdown of such a semiconductor device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a semiconductor device according to the embodiment; 
         FIG. 2  is a perspective cross-sectional view including a II-II cross section of  FIG. 1 ; 
         FIG. 3  is a III-III cross-sectional view of  FIG. 1 ; 
         FIG. 4  is a IV-IV cross-sectional view of  FIG. 1 ; 
         FIG. 5  is a V-V cross-sectional view of  FIG. 4 ; 
         FIG. 6  is a VI-VI cross-sectional view of  FIG. 4 ; 
         FIGS. 7A to 7C  are plan views for describing the semiconductor device according to the embodiment; 
         FIG. 8  is a plan view illustrating a semiconductor device according to a first variation of the embodiment; 
         FIG. 9  is a plan view illustrating a semiconductor device according to a second variation of the embodiment; 
         FIG. 10  is a plan view of a semiconductor device according to a third variation of the embodiment; 
         FIG. 11  is a perspective cross-sectional view including a XI-XI cross section of  FIG. 10 ; 
         FIG. 12  is a XII-XII cross-sectional view of  FIG. 11 ; and 
         FIG. 13  is a XIII-XIII cross-sectional view of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a semiconductor device includes a first electrode, a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type, a third semiconductor region of the first conductivity type, a fourth semiconductor region of the second conductivity type, a fifth semiconductor region of the first conductivity type, a gate electrode, a sixth semiconductor region of the second conductivity type, a second electrode, and an interconnect portion. The first semiconductor region is provided on the first electrode and electrically connected to the first electrode. The second semiconductor region is electrically connected to the first electrode and provided around the first semiconductor region along a first plane crossing a first direction. The first direction is from the first electrode toward the first semiconductor region. The third semiconductor region is provided on the first semiconductor region and the second semiconductor region. An impurity concentration of the first conductivity type in the third semiconductor region is lower than an impurity concentration of the first conductivity type in the first semiconductor region. The fourth semiconductor region is provided on a portion of the third semiconductor region. The fifth semiconductor region is provided selectively on the fourth semiconductor region. The gate electrode opposes in a second direction with a gate insulating layer interposed, the fifth semiconductor region, the fourth semiconductor region, and the portion of the third semiconductor region. The second direction is perpendicular to the first direction. The sixth semiconductor region is provided on another portion of the third semiconductor region. An impurity concentration of the second conductivity type in the sixth semiconductor region is higher than an impurity concentration of the second conductivity type in the fourth semiconductor region. The second electrode is provided on the fourth semiconductor region and the fifth semiconductor region and electrically connected to the fourth semiconductor region, the fifth semiconductor region, and the sixth semiconductor region. The interconnect portion is electrically connected to the gate electrode, separated from the second electrode, and provided on the sixth semiconductor region with an insulating layer interposed. A proportion of a surface area along the first plane of the first semiconductor region positioned under the sixth semiconductor region to a surface area along the first plane of the second semiconductor region positioned under the sixth semiconductor region is smaller than a proportion of a surface area along the first plane of the first semiconductor region positioned under the fourth semiconductor region to a surface area along the first plane of the second semiconductor region positioned under the fourth semiconductor region. 
     Various embodiments are described below with reference to the accompanying drawings. 
     The drawings are schematic and conceptual; and the relationships between the thickness and width of portions, the proportions of sizes among portions, etc., are not necessarily the same as the actual values. The dimensions and proportions may be illustrated differently among drawings, even for identical portions. 
     In the specification and drawings, components similar to those described previously or illustrated in an antecedent drawing are marked with like reference numerals, and a detailed description is omitted as appropriate. 
     In the drawings and the description recited below, the notations of n + , n, n − , p + , and p indicate relative levels of the impurity concentrations. In other words, a notation marked with “+” indicates that the impurity concentration is relatively higher than that of a notation not marked with either “+” or “−;” and a notation marked with “−” indicates that the impurity concentration is relatively lower than that of a notation without any mark. In the case where both a p-type impurity and an n-type impurity are included in each region, these notations indicate relative levels of the net impurity concentrations after the impurities are compensated. 
     In the embodiments described below, each embodiment may be performed by inverting the p-type and the n-type of each semiconductor region. 
       FIG. 1  is a plan view of a semiconductor device according to the embodiment. 
       FIG. 2  is a perspective cross-sectional view including a II-II cross section of  FIG. 1 . 
       FIG. 3  is a III-III cross-sectional view of  FIG. 1 . 
       FIG. 4  is a IV-IV cross-sectional view of  FIG. 1 . 
       FIG. 5  is a V-V cross-sectional view of  FIG. 4 . 
       FIG. 6  is a VI-VI cross-sectional view of  FIG. 4 . 
     An insulating layer  13 , an emitter electrode  22 , and an interconnect portion  23   a  are not illustrated in  FIG. 2 . A gate insulating layer  11  is not illustrated in  FIG. 6 . 
     The semiconductor device  100  is an RC-IGBT. The semiconductor device  100  includes an n + -type (first conductivity-type) cathode region  1  (a first semiconductor region), a p + -type (second conductivity-type) collector region  2  (a second semiconductor region), an n − -type drift region  3  (a third semiconductor region), a p-type base region  4  (a fourth semiconductor region), an n + -type emitter region  5  (a fifth semiconductor region), a p + -type finger region  6  (a sixth semiconductor region), an n-type buffer region  7 , a p-type guard ring region  8 , a gate electrode  10 , a collector electrode  21 , an emitter electrode  22 , and a gate pad  23 . 
     An XYZ orthogonal coordinate system is used in the description of the embodiments. A direction from the collector electrode  21  toward the n + -type cathode region  1  is taken as a Z-direction (a first direction). Two mutually-orthogonal directions perpendicular to the Z-direction are taken as an X-direction (a third direction) and a Y-direction (a second direction). For the description, the direction from the collector electrode  21  toward the n + -type cathode region  1  is called “up;” and the reverse direction is called “down.” These directions are based on the relative positional relationship between the collector electrode  21  and the n + -type cathode region  1  and are independent of the direction of gravity. 
     As illustrated in  FIG. 1 , the emitter electrode  22  and the gate pad  23  are provided to be separated from each other on the upper surface of the semiconductor device  100 . The semiconductor device  100  includes a cell region CR that operates as an IGBT. The emitter electrode  22  is provided in the cell region CR. For example, in the semiconductor device  100 , multiple cell regions CR are provided in the X-direction. Multiple emitter electrodes  22  are provided respectively on the multiple cell regions CR. The gate pad  23  includes the interconnect portion  23   a.  The interconnect portion  23   a  is provided around each emitter electrode  22  along the X-Y plane (a first plane) perpendicular to the Z-direction. The insulating layer  13  is provided between the gate pad  23  and each emitter electrode  22  and around the gate pad  23 . 
     As illustrated in  FIG. 2 , the collector electrode  21  is provided at the lower surface of the semiconductor device  100 . The n + -type cathode region  1  and the p + -type collector region  2  are provided on the collector electrode  21  and electrically connected to the collector electrode  21 . As illustrated in  FIG. 2  and  FIG. 5 , the p + -type collector region  2  is provided around the n + -type cathode region  1  along the X-Y plane. 
     As illustrated in  FIG. 2 , the n-type buffer region  7  is provided on the n + -type cathode region  1  and the p + -type collector region  2 . The n − -type drift region  3  is provided on the n-type buffer region  7 . The p-type base region  4  is provided on a portion of the n − -type drift region  3 . The n + -type emitter region  5  is provided selectively on the p-type base region  4 . The gate electrode  10  opposes, in the Y-direction with the gate insulating layer  11  interposed, the portion of the n − -type drift region  3 , the p-type base region  4 , and the n + -type emitter region  5 . 
     The emitter electrode  22  is provided on the p-type base region  4 , the n + -type emitter region  5 , and the gate electrode  10  and is electrically connected to the p-type base region  4  and the n + -type emitter region  5 . As illustrated in  FIG. 2  and  FIG. 3 , an insulating layer  12  is provided between the gate electrode  10  and the emitter electrode  22 ; and the gate electrode  10  and the emitter electrode  22  are electrically isolated. 
     The p + -type finger region  6  is provided on another portion of the n − -type drift region  3 . As illustrated in  FIG. 6 , the p + -type finger region  6  is provided around the cell regions CR along the X-Y plane. As illustrated in  FIG. 3 , the gate electrode  10  is drawn upward at a position where the p + -type finger region  6  is provided. The gate electrode  10  and the interconnect portion  23   a  are provided on the p + -type finger region  6  with the insulating layer  13  interposed; and the gate electrode  10  is electrically connected to the interconnect portion  23   a.    
     In the example illustrated in  FIG. 4 , the emitter electrode  22  is provided on a portion of the p + -type finger region  6 ; and the p + -type finger region  6  is electrically connected to the emitter electrode  22 . Or, the p + -type finger region  6  may be electrically connected to the emitter electrode  22  via the p-type base region  4 . The p-type impurity concentration in the p + -type finger region  6  is higher than the p-type impurity concentration in the p-type base region  4 . For example, the lower end of the p + -type finger region  6  is positioned lower than the lower end of the p-type base region  4  and the lower end of the gate insulating layer  11 . 
     As illustrated in  FIG. 6 , the p-type guard ring region  8  is provided around the p + -type finger region  6  along the X-Y plane. For example, the p-type impurity concentration in the p + -type finger region  6  is higher than the p-type impurity concentration in the p-type guard ring region  8 . 
     The example illustrated in  FIG. 2  to  FIG. 6  will now be described in detail. 
     Each cell region CR includes multiple n + -type cathode regions  1 , a portion of the p + -type collector region  2 , a portion of the n − -type drift region  3 , multiple p-type base regions  4 , multiple n + -type emitter regions  5 , a portion of the n-type buffer region  7 , multiple gate electrodes  10 , and one emitter electrode  22 . 
     In each cell region CR as illustrated in  FIG. 5 , the multiple n + -type cathode regions  1  are separated from each other in the X-direction and the Y-direction. A length L 1  in the X-direction of the n + -type cathode region  1  is shorter than a length L 2  in the Y-direction of the n + -type cathode region  1 . For example, a distance D 1  between the n + -type cathode regions  1  adjacent to each other in the X-direction is shorter than a distance D 2  between the n + -type cathode regions  1  adjacent to each other in the Y-direction. The distance D 2  is shorter than the length L 2  and longer than the length L 1 . In the illustrated example, three n + -type cathode regions  1  are arranged in the X-direction in one cell region CR. The number of the n + -type cathode regions  1  arranged in the X-direction in one cell region CR is not limited to the example and is modifiable as appropriate. 
     As illustrated in  FIG. 6 , the gate electrode  10  and the p-type base region  4  are provided alternately in the Y-direction in each cell region CR. Multiple n + -type emitter regions  5  are selectively provided on each p-type base region  4 . 
     An other portion of the p + -type collector region  2 , the p + -type finger region  6 , and the interconnect portion  23   a  are provided around each cell region CR along the X-Y plane. That is, a portion of the p + -type finger region  6  is provided between the multiple p-type base regions  4  and the multiple gate electrodes  10  included in one cell region CR in the X-direction and the multiple p-type base regions  4  and the multiple gate electrodes  10  included in another one cell region CR. 
     The proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p + -type finger region  6  is smaller than the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p-type base region  4  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p-type base region  4 . The surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  may be greater than zero or may be zero. In other words, the n + -type cathode region  1  may not be provided under the p + -type finger region  6 . 
     The relationships of the proportions will now be described in detail with reference to  FIG. 7A  to  FIG. 7C . 
       FIGS. 7A to 7C  are plan views for describing the semiconductor device according to the embodiment. 
       FIG. 7A  to  FIG. 7C  correspond to a V-V cross-sectional view of  FIG. 4 . A portion of the p + -type collector region  2  positioned under the p + -type finger region  6  is taken as a region R 1 . An other portion of the p + -type collector region  2  positioned under the p-type base region  4  is taken as a region R 2 . In  FIG. 7A , only the region R 1  is illustrated by marking with dots; and the other portions are illustrated by broken lines. In  FIG. 7B , only the region R 2  is illustrated by marking with dots; and the other portions are illustrated by broken lines. In  FIG. 7C , only the n + -type cathode region  1  positioned under the p-type base region  4  is illustrated by marking with dots; and the other portions are illustrated by broken lines. 
     A surface area A 1  along the X-Y plane of the region R 1  is illustrated by the surface area of the region marked with the dots illustrated in  FIG. 7A . A surface area A 2  along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  is zero. A surface area A 3  along the X-Y plane of the region R 2  is illustrated by the surface area of the region marked with the dots illustrated in  FIG. 7B . A surface area A 4  along the X-Y plane of the n + -type cathode region  1  is illustrated by the surface area of the region marked with the dots illustrated in  FIG. 7C . The proportion of the surface area A 2  to the surface area A 1  is zero and is smaller than the proportion of the surface area A 4  to the surface area A 3 . 
     The operation of the semiconductor device  100  will now be described. 
     A voltage that is not less than a threshold is applied to the gate electrode  10  in a state in which a voltage that is positive with respect to the emitter electrode  22  is applied to the collector electrode  21 . Thereby, a channel (an inversion layer) is formed in the p-type base region  4 ; and an IGBT operation is started in the cell region CR. Electrons from the emitter electrode  22  pass through the n + -type emitter region  5  and the channel and flow toward the n − -type drift region  3 . Holes from the collector electrode  21  pass through the p + -type collector region  2  and flow toward the n − -type drift region  3 . Subsequently, when the voltage applied to the gate electrode  10  becomes lower than the threshold, the channel in the p-type base region  4  disappears; and the IGBT operation ends. 
     For example, a bridge circuit is configured using multiple semiconductor devices  100 . When the IGBT operation of one semiconductor device  100  of the bridge circuit ends, an induced electromotive force is applied to the emitter electrode  22  of another semiconductor device  100  by an inductance component of the circuit. When the induced electromotive force is applied to the emitter electrode  22 , the other semiconductor device  100  operates as a diode. In the diode operation, holes from the emitter electrode  22  pass through the p-type base region  4  and the p + -type finger region  6  and flow toward the n − -type drift region  3 . Electrons from the collector electrode  21  pass through the n + -type cathode region  1  and flow toward the n − -type drift region  3 . 
     When the diode operation of the semiconductor device  100  ends, the holes that have accumulated in the n − -type drift region  3  pass through the p-type base region  4  and the p + -type finger region  6  and are ejected to the emitter electrode  22 . The electrons that have accumulated in the n − -type drift region  3  pass through the n + -type cathode region  1  and are ejected to the collector electrode  21 . 
     The p + -type collector region  2  includes, for example, a trigger region  2   t  as illustrated in  FIG. 5 . The multiple n + -type cathode regions  1  are provided around the trigger region  2   t  along the X-Y plane. 
     Specifically, a portion of the trigger region  2   t  is provided in one of the multiple cell regions CR. The portion of the trigger region  2   t  in the one of the multiple cell regions CR is positioned between a portion of the multiple n + -type cathode regions  1  of the one of the multiple cell regions CR and another portion of the multiple n + -type cathode regions  1  of the one of the multiple cell regions CR in the Y-direction. 
     An other portion of the trigger region  2   t  is provided in another one of the multiple cell regions CR. The other one of the multiple cell regions CR is adjacent to the one of the multiple cell regions CR in the X-direction. The other portion of the trigger region  2   t  in the other one of the multiple cell regions CR is positioned between a portion of the multiple n + -type cathode regions  1  of the other one of the multiple cell regions CR and another portion of the multiple n + -type cathode regions  1  of the other one of the multiple cell regions CR in the Y-direction. 
     For example, the trigger region  2   t  is provided at the central portion of the p + -type collector region  2  in the X-direction and the Y-direction. The n + -type cathode region  1  is not provided in the trigger region  2   t.  A length L 3  in the X-direction of the trigger region  2   t  and a length L 4  in the Y-direction of the trigger region  2   t  are longer than the distance D 1  and longer than the distance D 2 . By providing the trigger region  2   t,  injection of the holes into the n − -type drift region  3  can be faster when starting the IGBT operation. 
     Examples of the materials of the components will now be described. 
     The n + -type cathode region  1 , the p + -type collector region  2 , the n − -type drift region  3 , the p-type base region  4 , the n + -type emitter region  5 , the p + -type finger region  6 , the n-type buffer region  7 , and the p-type guard ring region  8  include silicon, silicon carbide, gallium nitride, or gallium arsenide as semiconductor materials. In the case where silicon is used as the semiconductor material, arsenic, phosphorus, or antimony can be used as an n-type impurity. Boron can be used as a p-type impurity. 
     The gate electrode  10  includes a conductive material such as polysilicon, etc. 
     The gate insulating layer  11 , the insulating layer  12 , and the insulating layer  13  include an insulating material such as silicon oxide, etc. 
     The collector electrode  21 , the emitter electrode  22 , and the gate pad  23  include a metal such as aluminum, etc. 
     Effects of the embodiment will now be described. 
     When the diode operation of the semiconductor device  100  ends, the holes that have accumulated in the n − -type drift region  3  pass through the p-type base region  4  and the p + -type finger region  6  and are ejected to the emitter electrode  22  as described above. The p-type impurity concentration in the p + -type finger region  6  is higher than the p-type impurity concentration in the p-type base region  4 . Therefore, more holes flow in the p + -type finger region  6  than in the p-type base region  4  of the cell region CR. 
     The emitter electrode  22  is provided on the entire surface of the cell region CR but is not provided or is provided only partially on the p + -type finger region  6 . Or, the emitter electrode  22  is not provided on the p + -type finger region  6 ; and the p + -type finger region  6  is electrically connected to the emitter electrode  22  via the p-type base region  4 . This is because the interconnect portion  23   a  is provided on the p + -type finger region  6 . Therefore, the holes that flow in the p + -type finger region  6  are not ejected easily to the emitter electrode  22  compared to the holes flowing in the p-type base region  4 ; and the time until being ejected to the emitter electrode  22  is long. As a result, the potential in the p + -type finger region  6  may increase; and breakdown of the semiconductor device  100  at the vicinity of the p + -type finger region  6  may occur. For example, the potential in the p + -type finger region  6  increases; and dielectric breakdown occurs between the p + -type finger region  6  and the gate electrode  10 . 
     In the semiconductor device  100  according to the embodiment, the proportion of the surface area of the n + -type cathode region  1  positioned under the p + -type finger region  6  to the surface area of the p + -type collector region  2  positioned under the p + -type finger region  6  is smaller than the proportion of the surface area of the n + -type cathode region  1  positioned under the p-type base region  4  to the surface area of the p + -type collector region  2  positioned under the p-type base region  4 . In other words, under the p + -type finger region  6 , the surface area of the n + -type cathode region  1  is small; or the n + -type cathode region  1  is not provided. According to this configuration, the injection of the electrons into a portion of the n − -type drift region  3  positioned under the p + -type finger region  6  in the diode operation of the semiconductor device  100  is suppressed. By suppressing the injection of the electrons into the portion of the n − -type drift region  3 , the injection of the holes from the p + -type finger region  6  into the portion of the n − -type drift region  3  also is suppressed. Thereby, when the diode operation of the semiconductor device  100  ends, the amount of the holes passing through the p + -type finger region  6  and flowing toward the emitter electrode  22  can be reduced. As a result, the likelihood of breakdown of the semiconductor device  100  can be reduced. 
     It is desirable for the lower end of the p + -type finger region  6  to be lower than the lower end of the gate electrode  10  and to overlap a portion of the gate electrode  10  (the end portion in the X-direction of the gate electrode  10 ) in the Z-direction. According to this configuration, electric field concentration at the end portion of the gate electrode  10  can be relaxed when the semiconductor device  100  is in the off-state; and the likelihood of breakdown of the semiconductor device  100  can be reduced further. 
     It is more desirable for the n + -type cathode region  1  not to be provided under the p + -type finger region  6 . Thereby, in the diode operation of the semiconductor device  100 , the injection of carriers into the portion where the p + -type finger region  6  is provided can be suppressed further. 
     First Variation 
       FIG. 8  is a plan view illustrating a semiconductor device according to a first variation of the embodiment. 
       FIG. 8  illustrates an X-Y cross section passing through the n + -type cathode region  1  and the p + -type collector region  2  of the semiconductor device  110  according to the first variation. In the semiconductor device  110  illustrated in  FIG. 8 , the distance D 1  between the n + -type cathode regions  1  adjacent to each other in the X-direction is long compared to that of the semiconductor device  100 . For example, the distance D 1  is longer than the length L 1  in the X-direction of the n + -type cathode region  1 . 
     In the semiconductor device  110 , similarly to the semiconductor device  100 , the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p + -type finger region  6  is smaller than the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p-type base region  4  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p-type base region  4 . According to the first variation, the injection of carriers into the portion where the p + -type finger region  6  is provided in the diode operation of the semiconductor device  110  can be suppressed. The likelihood of breakdown of the semiconductor device  110  can be reduced thereby. 
     Second Variation 
       FIG. 9  is a plan view illustrating a semiconductor device according to a second variation of the embodiment. 
       FIG. 9  illustrates an X-Y cross section passing through the n + -type cathode region  1  and the p + -type collector region  2  of the semiconductor device  120  according to the second variation. In the semiconductor device  120  illustrated in  FIG. 9 , multiple n + -type cathode regions  1  are provided in the X-direction and the Y-direction in each cell region CR. 
     The length L 1  in the X-direction of the n + -type cathode region  1  is, for example, substantially the same as the length L 2  in the Y-direction of the n + -type cathode region  1 . The length L 1  and the length L 2  are longer than the distance D 1  between the n + -type cathode regions  1  adjacent to each other in the X-direction and longer than the distance D 2  between the n + -type cathode regions  1  adjacent to each other in the Y-direction. 
     In the semiconductor device  120  as well, the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p + -type finger region  6  is smaller than the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p-type base region  4  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p-type base region  4 . According to the second variation, the likelihood of breakdown of the semiconductor device  120  can be reduced. 
     As long as the relationship of the proportions described above is satisfied, the size of the n + -type cathode region  1 , the number of the n + -type cathode regions  1 , the distance between the n + -type cathode regions  1 , etc., are modifiable as appropriate as illustrated in  FIG. 8  and  FIG. 9 . 
     Third Variation 
       FIG. 10  is a plan view of a semiconductor device according to a third variation of the embodiment. 
       FIG. 11  is a perspective cross-sectional view including a XI-XI cross section of  FIG. 10 . 
       FIG. 12  is a XII-XII cross-sectional view of  FIG. 11 . 
       FIG. 13  is a XIII-XIII cross-sectional view of  FIG. 11 . 
     The emitter electrode  22 , the interconnect portion  23   a,  etc., are not illustrated in  FIG. 11 . 
     In the semiconductor device  130  according to the third variation as illustrated in  FIG. 10 , multiple emitter electrodes  22  are arranged in a circumferential direction around the Z-direction. In other words, in the semiconductor device  130 , the multiple cell regions CR are arranged in the circumferential direction around the Z-direction. The interconnect portion  23   a  of the gate pad  23  is provided around each cell region CR along the X-Y plane. For example, portions of the interconnect portion  23   a  extend radially from a position surrounded with the multiple emitter electrodes  22 . 
     As illustrated in  FIG. 12 , the multiple n + -type cathode regions  1  are arranged in the circumferential direction around the Z-direction. The p + -type collector region  2  is provided around each n + -type cathode region  1 . For example, the p + -type collector region  2  includes the trigger region  2   t.  The multiple n + -type cathode regions  1  are provided around the trigger region  2   t  along the X-Y plane. Portions of the p + -type collector region  2  extend radially with the trigger region  2   t  as the center. 
     In each cell region CR as illustrated in  FIG. 11  and  FIG. 13 , the multiple p-type base regions  4 , the multiple n + -type emitter regions  5 , and the multiple gate electrodes  10  extend in the X-direction. The p + -type finger region  6  is provided around each cell region CR along the X-Y plane and surrounds the multiple p-type base regions  4 , the multiple n + -type emitter regions  5 , and the multiple gate electrodes  10 . The p + -type finger region  6  is positioned between the p + -type collector region  2  and the interconnect portion  23   a  in the Z-direction. Portions of the p + -type finger region  6  extend radially from a position surrounded with the multiple cell regions CR. 
     In the semiconductor device  130  as well, the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p + -type finger region  6  is smaller than the proportion of the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p-type base region  4  to the surface area along the X-Y plane of the p + -type collector region  2  positioned under the p-type base region  4 . In the example illustrated in  FIG. 11  and  FIG. 12 , the surface area along the X-Y plane of the n + -type cathode region  1  positioned under the p + -type finger region  6  is zero. The likelihood of breakdown of the semiconductor device  130  can be reduced thereby. 
     In each of the embodiments described above, it is possible to confirm the relative levels of the impurity concentrations between the semiconductor regions by using, for example, a SCM (scanning capacitance microscope). The carrier concentration in each semiconductor region can be considered to be equal to the activated impurity concentration in each semiconductor region. Accordingly, the relative levels of the carrier concentrations between the semiconductor regions also can be confirmed using SCM. It is possible to measure the impurity concentration in each semiconductor region by, for example, SIMS (secondary ion mass spectrometry). 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. The above embodiments can be practiced in combination with each other.