Semiconductor device

Abstract

To preferably improve characteristics such as a turn-on power loss in a semiconductor device.SOLUTION: A semiconductor device in which a plurality of trench parts is provided on an upper surface side of a semiconductor substrate and in which a first mesa part and a second mesa part being regions between the trench parts are formed comprises a drift region of a first conductivity type, a base region of a second conductivity type provided in the first and second mesa parts above the drift region, and a high-concentration region of the first conductivity type provided between the drift and base regions in a depth direction of the semiconductor substrate and having a higher doping concentration than the drift region. A depth position of a lower end of the high-concentration region between the base and drift regions of the first mesa part is deeper than a depth position of a lower end of the high-concentration region between the base and drift regions of the second mesa part.SELECTED DRAWING: Figure 7a

Description

[Technical field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, semiconductor devices such as insulated gate bipolar transistors (IGBTs) are known (see, for example, Patent Document 1). Patent Document 1: JP 2007-311627 A Summary of the Invention [Problem to be solved by the invention]

[0003] In a semiconductor device, it is preferable to improve characteristics such as turn-on loss. [Means for solving the problem]

[0004] A first aspect of the present invention provides a semiconductor device having a plurality of trenches on an upper surface side of a semiconductor substrate, and a first mesa portion and a second mesa portion being regions between the trenches.

[0005] The semiconductor device may include a drift region of a first conductivity type, a base region of a second conductivity type provided in the first mesa portion and the second mesa portion above the drift region, and a high concentration region of the first conductivity type provided between the drift region and the base region in a depth direction of the semiconductor substrate, the high concentration region having a doping concentration higher than that of the drift region.

[0006] In any of the above semiconductor devices, the depth position of the lower end of the high concentration region between the base region and the drift region of the first mesa portion may be deeper than the depth position of the lower end of the high concentration region between the base region and the drift region of the second mesa portion.

[0007] In any of the above semiconductor devices, an integral concentration obtained by integrating the doping concentration of the high concentration region between the base region and the drift region of the first mesa portion in the depth direction may be higher than an integral concentration obtained by integrating the doping concentration of the high concentration region between the base region and the drift region of the second mesa portion in the depth direction.

[0008] In a second aspect of the present invention, there is provided a semiconductor device in which a plurality of trenches are provided on the upper surface side of a semiconductor substrate, and at least a first mesa portion and a second mesa portion are formed.

[0009] The semiconductor device may include a drift region of a first conductivity type, a base region of a second conductivity type provided in the first mesa portion and the second mesa portion above the drift region, and a high concentration region of the first conductivity type provided between the drift region and the base region in a depth direction of the semiconductor substrate, the high concentration region having a doping concentration higher than that of the drift region.

[0010] In any of the above semiconductor devices, an integral concentration obtained by integrating the doping concentration of the high concentration region between the base region and the drift region of the first mesa portion in the depth direction may be higher than an integral concentration obtained by integrating the doping concentration of the high concentration region between the base region and the drift region of the second mesa portion in the depth direction.

[0011] In any of the above semiconductor devices, upper ends of the high concentration regions in the first mesa portion and the second mesa portion may be in contact with the base region.

[0012] In any of the semiconductor devices described above, upper ends of the high concentration regions in the first mesa portion and the second mesa portion may be provided at the same depth position and may have the same doping concentration.

[0013] Any of the above semiconductor devices may further include an emitter region of a first conductivity type selectively provided on an upper surface side of the semiconductor substrate and having a doping concentration higher than that of the drift region.

[0014] In any of the semiconductor devices described above, the high concentration region may be provided below the emitter region of the first mesa portion and below the emitter region of the second mesa portion.

[0015] Any of the above semiconductor devices may further include a contact region of a second conductivity type selectively provided on an upper surface side of the semiconductor substrate and having a doping concentration higher than that of the base region.

[0016] In any of the above semiconductor devices, the high concentration region may be provided below the contact region of the first mesa portion and below the contact region of the second mesa portion.

[0017] Any of the above semiconductor devices may include, as the plurality of trench portions, one or more dummy trench portions and one or more gate trench portions.

[0018] In any of the above semiconductor devices, the dummy trench portions and the gate trench portions may each extend linearly in an extension direction when viewed from above, and may be arranged at predetermined intervals in an arrangement direction.

[0019] Any of the above semiconductor devices may comprise an edge termination structure that is provided to surround an active region of the semiconductor substrate and includes at least one of a guard ring, a field plate, and a resurf.

[0020] Any of the above semiconductor devices may further include a well region of a second conductivity type that is provided in a predetermined range at an end of the active region and is formed deeper than the trench portion in the depth direction.

[0021] In any of the above semiconductor devices, an end portion of the high concentration region in the extension direction may be separated from the well region in a top view.

[0022] In any of the above semiconductor devices, ends of the high concentration region in the extension direction may extend to the same position in the first mesa portion and the second mesa portion toward the well region in a top view.

[0023] Any of the above semiconductor devices may include a first lower surface region of a second conductivity type provided on a lower surface side of the semiconductor substrate.

[0024] In any of the semiconductor devices described above, the first lower surface region may be located below the first mesa portion and the second mesa portion.

[0025] In any of the above semiconductor devices, the high concentration region may be an accumulation region.

[0026] Any of the above semiconductor devices may include a second lower surface region of the first conductivity type provided on the lower surface side of the semiconductor substrate.

[0027] In any of the above semiconductor devices, the semiconductor substrate may be any of a silicon substrate, a silicon carbide substrate, and a nitride semiconductor substrate.

[0028] The above summary of the invention does not list all the features of the present invention. Subcombinations of these features may also be inventions. [Brief description of the drawings]

[0029] [Figure 1] 1 is a diagram partially illustrating the top surface of a semiconductor device 100 according to an embodiment of the present invention. [Figure 2a] FIG. 2 is a diagram showing an example of a cross section taken along the line dd' in FIG. [Figure 2b] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 2c] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 2d] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 2e]2C is a diagram showing a concentration distribution of a crystal defect layer 89 in the n-n' cross section in FIG. 2D. [Figure 2f] 1 is a diagram showing an example of a cross section of a semiconductor device 150 according to an embodiment of the present invention. [Figure 2g] 1 is a diagram showing another example of a cross section of a semiconductor device 150 according to an embodiment of the present invention. [Diagram 3] 2b is a diagram showing an example of a doping concentration distribution in the ee' cross section and the ff' cross section of FIG. 2a. FIG. [Figure 4] FIG. 13 is a diagram showing an example of the waveform of a collector current Ic at the time of turn-on. [Diagram 5] 2b is a diagram showing another example of the doping concentration distribution in the ee' cross section and the ff' cross section of FIG. 2a. FIG. [Figure 6] 1 is a diagram showing an electron current and a displacement current at the time of turn-on in a semiconductor device 100 including a first accumulation region 16-1, a second accumulation region 16-2, and a third accumulation region 16-3. [Figure 7a] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 7b] 7B is a diagram showing an example of doping concentration distribution in the ee' cross sections, the ff' cross sections, and the gg' cross sections in FIG. 7a. FIG. [Figure 8] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 9] 13 is a cross-sectional view for explaining an example of the arrangement of floating regions 84. FIG. [Figure 10] 2 is a top view showing an example of the arrangement of floating regions 84 in a diode section 80. FIG. [Figure 11] 2 is a top view showing an example of the arrangement of floating regions 84 in a diode section 80. FIG. [Figure 12] 13 is a top view showing another example of the arrangement of the floating region 84 in the diode section 80. FIG. [Figure 13] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 14] 1. FIG. 4 is a diagram showing another example of the dd' cross section in FIG. [Figure 15] 13 is a diagram showing another example of the arrangement of the lifetime killer 88. FIG. [Figure 16] 2 is a diagram showing an example of the configuration of a diode section 80. FIG. [Figure 17] 13 is a diagram showing another example of the configuration of the diode section 80. FIG. [Figure 18] FIG. 2 is a diagram illustrating another example of the semiconductor device 100. [Figure 19] FIG. 2 is a diagram partially illustrating the top surface of a semiconductor device 200 according to another embodiment of the present invention. [Figure 20] 20 is a diagram showing an example of the dd' cross section in FIG. 19. FIG. [Figure 21a] FIG. 2 is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. [Figure 21b] FIG. 21b is a diagram showing an example of the s-s' cross section in FIG. 21a. [Figure 21c] FIG. 21b is a diagram showing an example of the t-t' cross section in FIG. 21a. [Figure 22] FIG. 11 is a cross-sectional view of a semiconductor device 350 of a comparative example. [Figure 23a] FIG. 2 is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. [Figure 23b] FIG. 23b is a diagram showing an example of the uu' cross section in FIG. 23a. [Figure 23c] FIG. 23b is a diagram showing an example of the vv' cross section in FIG. 23a. [Figure 24] FIG. 2 is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. [Diagram 25] FIG. 2 is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. [Figure 26] 1 is a diagram showing an example of a semiconductor chip 120 according to an embodiment of the present invention. [Figure 27a] FIG. 27 is an enlarged view of an area A in FIG. [Figure 27b] FIG. 27b is an enlarged view of region B1 in FIG. 27a. [Figure 27c] FIG. 27b is an enlarged view of region B2 in FIG. [Fig. 27d] FIG. 27b is a diagram showing an example of the cross section taken along the line hh'. [Figure 27e] FIG. 27B is a diagram showing an example of the j-j' cross section in FIG. 27B. [Figure 28a] FIG. 27 is another enlarged view of the area A in FIG. [Figure 28b] FIG. 28b is an enlarged view of region C1 in FIG. 28a. [Figure 28c] FIG. 28b is an enlarged view of region C2 in FIG. [Fig. 28d] FIG. 28B is a diagram showing an example of the k-k' cross section in FIG. 28B. [Figure 28e] FIG. 28B is a diagram showing an example of the mm' cross section in FIG. 28B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0031] In this specification, one side in a direction parallel to the depth direction of a semiconductor substrate is referred to as "upper" and the other side as "lower." Of the two main surfaces of a substrate, layer, or other member, one surface is referred to as the upper surface and the other surface is referred to as the lower surface. The directions of "upper" and "lower" are not limited to the direction of gravity.

[0032] In each embodiment, the first conductivity type is n-type and the second conductivity type is p-type, but the first conductivity type may be p-type and the second conductivity type may be n-type. In this case, the conductivity types of the substrate, layer, region, etc. in each embodiment are opposite polarities.

[0033] FIG. 1 is a diagram partially illustrating the upper surface of a semiconductor device 100 according to an embodiment of the present invention. The semiconductor device 100 of this example is a semiconductor chip including a transistor section 70, a diode section 80, and a boundary section 90. The boundary section 90 may be a part of the transistor section 70. The transistor section 70 includes a transistor such as an IGBT. The diode section 80 is provided adjacent to the transistor section 70 on the upper surface of a semiconductor substrate, and includes a diode such as an FWD (Free Wheel Diode). The boundary section 90 is provided between the transistor section 70 and the diode section 80 on the upper surface of the semiconductor substrate. FIG. 1 shows the upper surface of the chip around the chip end, and other areas are omitted.

[0034] 1 shows an active region of the semiconductor substrate in semiconductor device 100, but semiconductor device 100 may have an edge termination structure surrounding the active region. The active region refers to a region through which current flows when semiconductor device 100 is controlled to be in an on-state. The edge termination structure relieves electric field concentration on the upper surface side of the semiconductor substrate. The edge termination structure has a structure such as a guard ring, a field plate, a resurf, or a combination of these.

[0035] The semiconductor device 100 of this example includes a gate trench portion 40, a dummy trench portion 30, a well region 11, an emitter region 12, a base region 14, and a contact region 15 formed inside the upper surface side of a semiconductor substrate. The gate trench portion 40 and the dummy trench portion 30 are an example of a trench portion. The semiconductor device 100 of this example also includes an emitter electrode 52 and a gate metal layer 50 provided above the upper surface of the semiconductor substrate. The emitter electrode 52 and the gate metal layer 50 are provided separately from each other.

[0036] An interlayer insulating film is formed between the emitter electrode 52 and the gate metal layer 50 and the upper surface of the semiconductor substrate, but is omitted in Fig. 1. In the interlayer insulating film of this example, contact holes 56, 49, and 54 are formed so as to penetrate the interlayer insulating film.

[0037] The emitter electrode 52 contacts the emitter region 12, the contact region 15, and the base region 14 on the upper surface of the semiconductor substrate through a contact hole 54. The emitter electrode 52 is also connected to a dummy conductive portion in the dummy trench portion 30 through a contact hole 56. A connection portion 25 made of a conductive material such as polysilicon doped with impurities may be provided between the emitter electrode 52 and the dummy conductive portion. The connection portion 25 is formed on the upper surface of the semiconductor substrate.

[0038] The gate metal layer 50 contacts the gate runner 48 through the contact hole 49. The gate runner 48 is formed of polysilicon doped with impurities or the like. The gate runner 48 is connected to the gate conductive portion in the gate trench portion 40 on the upper surface of the semiconductor substrate. The gate runner 48 is not connected to the dummy conductive portion in the dummy trench portion 30. The gate runner 48 in this example is formed from below the contact hole 49 to the tip of the gate trench portion 40. At the tip of the gate trench portion 40, the gate conductive portion is exposed to the upper surface of the semiconductor substrate and contacts the gate runner 48.

[0039] The emitter electrode 52 and the gate metal layer 50 are formed of a material containing metal. For example, at least a portion of each electrode is formed of aluminum or an aluminum-silicon alloy. Each electrode may have a barrier metal made of titanium or a titanium compound under the region made of aluminum, and may have a plug made of tungsten in the contact hole.

[0040] The one or more gate trench portions 40 and the one or more dummy trench portions 30 are arranged at predetermined intervals along a predetermined arrangement direction in the region of the transistor portion 70. In the transistor portion 70, the one or more gate trench portions 40 and the one or more dummy trench portions 30 may be formed alternately along the arrangement direction.

[0041] The gate trench portion 40 of this example may have two extension portions extending along an extension direction parallel to the upper surface of the semiconductor substrate and perpendicular to the arrangement direction, and a connection portion connecting the two extension portions. At least a part of the connection portion is preferably formed in a curved shape. By connecting the ends of the two extension portions of the gate trench portion 40, electric field concentration at the ends of the extension portions can be alleviated. The gate runner 48 may be connected to the gate conductive portion at the connection portion of the gate trench portion 40.

[0042] The dummy trench portion 30 of this example is provided between the extension portions of the gate trench portion 40. The dummy trench portion 30 may have a U-shape on the upper surface of the semiconductor substrate, similar to the gate trench portion 40. That is, the dummy trench portion 30 of this example has two extension portions extending along the extension direction and a connection portion connecting the two extension portions. In another example, the dummy trench portion 30 may have a linear shape extending in the extension direction.

[0043] A plurality of dummy trench portions 30 are continuously arranged in the boundary portion 90 and the diode portion 80. A plurality of dummy trench portions 30 may also be continuously arranged in a region of the transistor portion 70 adjacent to the boundary portion 90. In this example, the linear extension portion of each trench portion is regarded as one trench portion.

[0044] The emitter electrode 52 is formed above the gate trench portion 40, the dummy trench portion 30, the well region 11, the emitter region 12, the base region 14, and the contact region 15. The well region 11 is of the second conductivity type, and is formed in a predetermined range from the end of the active region on the side where the gate metal layer 50 is provided. The diffusion depth of the well region 11 may be deeper than the depth of the gate trench portion 40 and the dummy trench portion 30. Part of the regions of the gate trench portion 40 and the dummy trench portion 30 on the gate metal layer 50 side are formed in the well region 11. The bottom of the end of the dummy trench portion 30 in the extension direction may be covered by the well region 11.

[0045] A base region 14 is formed in the mesa portion between the trench portions. The base region 14 is of a second conductivity type having a lower doping concentration than the well region 11. In this example, the base region 14 is of a P-type. The mesa portion is a portion of the semiconductor substrate between two adjacent trench portions, and may be a portion extending from the top surface of the semiconductor substrate to the depth of the deepest bottom of each trench portion.

[0046] A contact region 15 of a second conductivity type having a higher doping concentration than the base region 14 is selectively formed on the upper surface of the base region 14 of the mesa portion. In this example, the contact region 15 is of P+ type. In the transistor portion 70, an emitter region 12 of a first conductivity type having a higher doping concentration than the semiconductor substrate is selectively formed on a part of the upper surface of the contact region 15. In this example, the emitter region 12 is of N+ type.

[0047] Each of the contact region 15 and the emitter region 12 is formed from one adjacent trench portion to the other adjacent trench portion. One or more contact regions 15 and one or more emitter regions 12 of the transistor portion 70 are formed so as to be exposed on the upper surface of the mesa portion alternately along the extension direction of the trench portion. Each of the contact region 15 and the emitter region 12 may contact one adjacent trench portion or the other adjacent trench portion over a predetermined length along the extension direction of each trench portion.

[0048] In another example, the contact region 15 and the emitter region 12 may be formed in a stripe shape along the extension direction of the trench portion in the mesa portion of the transistor section 70. For example, the emitter region 12 is formed in a region adjacent to the trench portion, and the contact region 15 is formed in a region sandwiched between the emitter regions 12.

[0049] In this example, no emitter region 12 is formed in the diode portion 80 and the mesa portion of the boundary portion 90. In addition, a contact region 15 is formed in the mesa portion of the diode portion 80 in a region facing at least one contact region 15 in the transistor portion 70. In the mesa portion of the boundary portion 90, a contact region 15 is formed in a region facing the contact region 15 and emitter region 12 of the transistor portion 70. The boundary portion 90 may include a plurality of mesa portions. In the boundary portion 90, in one or more mesa portions located on the diode portion 80 side, the area of ​​the upper surface of the semiconductor substrate of the contact region 15 may be smaller than that of the mesa portion adjacent to the transistor portion 70. In the boundary portion 90, in one or more mesa portions located on the diode portion 80 side, the base region 14 may be exposed on the upper surface of the semiconductor substrate.

[0050] In the transistor section 70, the contact hole 54 is formed above each of the contact region 15 and the emitter region 12. The contact hole 54 is not formed in the region corresponding to the base region 14 and the well region 11.

[0051] In the diode section 80, the contact hole 54 is formed above the contact region 15 and the base region 14. In this example, the contact hole 54 is not formed in the base region 14 that is closest to the gate metal layer 50 among the multiple base regions 14 in the mesa portion of the diode section 80.

[0052] The diode section 80 has a cathode region 82 of a first conductivity type on the lower surface side of the semiconductor substrate. In this example, the cathode region 82 is an N+ type. In FIG. 1, the region where the cathode region 82 is provided in the top view of the semiconductor substrate is indicated by a dashed line. The diode section 80 may be a region where the cathode region 82 is projected onto the upper surface of the semiconductor substrate. The region where the cathode region 82 is projected onto the upper surface of the semiconductor substrate may be separated from the contact region 15 in the +X-axis direction.

[0053] In the diode section 80, a P+ type collector region may be formed in a region where the cathode region 82 is not formed on the lower surface of the semiconductor substrate. In this example, for the dummy trench section 30 or mesa section 95 on the upper surface of the semiconductor substrate onto which the cathode region 82 on the lower surface 23 is projected, a collector region is formed at a position where the end of the outer periphery side (direction in the -X-axis direction) of the contact hole 54 of the mesa section 95 is projected onto the lower surface of the semiconductor substrate. As an example, in the dummy trench section 30 or mesa section 95 in which the cathode region 82 is formed on a part of the lower surface of the semiconductor substrate, the dummy trench section 30 or mesa section 95 up to the end of the dummy trench section 30 in the extension direction (including the part connected in a U-shape) may be conveniently called the diode section 80 even if a collector region is formed on the lower surface of the semiconductor substrate. The transistor section 70 may be a region where the trench section or mesa section is formed among the region where the collector region is projected onto the upper surface of the semiconductor substrate.

[0054] At the boundary portion 90, the contact hole 54 is formed above the contact region 15. In this example, the contact hole 54 is not formed for the base region 14 at the boundary portion 90. At the boundary portion 90, in one or more mesa portions located on the diode portion 80 side, the contact hole 54 may be formed above the base region 14. In this example, the contact hole 54 in the transistor portion 70, the contact hole 54 in the diode portion 80, and the contact hole 54 in the boundary portion 90 have the same length in the extension direction of each trench portion.

[0055] The semiconductor device 100 has a first conductivity type accumulation region 16 and a first conductivity type high concentration region 17 selectively formed below a base region 14 inside a semiconductor substrate. In Fig. 1, the ranges in which the accumulation region 16 and the high concentration region 17 are formed are indicated by dashed dotted lines. The accumulation region 16 is formed in a transistor section 70, and the high concentration region 17 is formed in a diode section 80.

[0056] Fig. 2a is a diagram showing an example of a dd' cross section in Fig. 1. In this cross section, the semiconductor device 100 of this example has a semiconductor substrate 10, an interlayer insulating film 38, an emitter electrode 52, and a collector electrode 24. The emitter electrode 52 is formed on an upper surface 21 of the semiconductor substrate 10 and the interlayer insulating film 38.

[0057] Collector electrode 24 is formed on lower surface 23 of semiconductor substrate 10. Emitter electrode 52 and collector electrode 24 are made of a conductive material such as metal. In this specification, the direction connecting emitter electrode 52 and collector electrode 24 is referred to as the depth direction.

[0058] The semiconductor substrate 10 may be a silicon substrate, a silicon carbide substrate, a nitride semiconductor substrate such as gallium nitride, etc. In this example, the semiconductor substrate 10 is a silicon substrate. A P-type base region 14 is formed on the upper surface side of the semiconductor substrate 10.

[0059] In this cross section, an N+ type emitter region 12, a P- type base region 14, and one or more N+ type accumulation regions 16 are formed in this order from the upper surface 21 side on the upper surface 21 side of the transistor section 70. In this cross section, a P- type base region 14 and one or more N+ type high concentration regions 17 are formed in this order from the upper surface 21 side on the upper surface 21 side of the diode section 80. In this cross section, a P+ type contact region 15 and a P- type base region 14 are formed in this order from the upper surface 21 side on the upper surface 21 side of the boundary section 90.

[0060] In the transistor section 70, an N-type drift region 18 is formed on the lower surface of the accumulation region 16. By providing one or more accumulation regions 16 having a higher concentration than the drift region 18 between the drift region 18 and the base region 14, it is possible to enhance the carrier injection enhancement effect (IE effect) and reduce the on-voltage.

[0061] In this example, the region sandwiched between the trench portions inside the semiconductor substrate 10 is the mesa portion 95. Specifically, it may be a portion of the semiconductor substrate 10 sandwiched between two adjacent trench portions, and may be a portion from the upper surface 21 of the semiconductor substrate 10 to the depth of the deepest bottom of either of the two adjacent trench portions. One or more accumulation regions 16 are formed in each mesa portion 95 of the transistor portion 70. In this example, each mesa portion 95 of the transistor portion 70 is provided with a first accumulation region 16-1, a second accumulation region 16-2, and a third accumulation region 16-3 at different positions in the depth direction of the semiconductor substrate 10. The accumulation region 16 may be provided so as to cover the entire lower surface of the base region 14 in each mesa portion 95.

[0062] One or more high concentration regions 17 are formed in each mesa portion 95 of the diode portion 80. In this example, a first high concentration region 17-1 and a second high concentration region 17-2 are provided in the mesa portion 95 of the diode portion 80 at different positions in the depth direction of the semiconductor substrate 10. The high concentration regions 17 may be provided so as to cover the entire lower surface of the base region 14 in each mesa portion 95. No high concentration region 17 is formed in each mesa portion 95 at the boundary portion.

[0063] By providing one or more N+ type high concentration regions 17 in each mesa portion 95 of the diode portion 80, one or more N+ type high concentration regions 17 having a higher concentration than the drift region 18 are inserted between the base region 14, which is the P type anode layer of the diode portion 80, and the N type drift region 18. In the one or more high concentration regions 17, the concentration of holes is reduced due to the charge neutral condition compared to the drift region 18. That is, the one or more high concentration regions 17 suppress the injection of holes from the base region 14 to the drift region 18. This significantly reduces the injection efficiency of minority carriers. The more the number of high concentration regions 17, the more the injection efficiency of minority carriers can be reduced. This significantly reduces the reverse recovery characteristic of the diode portion 80, especially the recovery current.

[0064] In this example, the injection efficiency of minority carriers means the ratio of the current density of minority carriers (hole current density in this example) to the total current density flowing through the emitter electrode 52 when a voltage higher than that of the collector electrode 24 is applied to the emitter electrode 52. The sum of the hole current density and the electron current density is the total current density.

[0065] In each of the transistor portion 70, the diode portion 80, and the boundary portion 90, an N+ type buffer region 20 is formed on the lower surface of the drift region 18. The buffer region 20 is formed on the lower surface side of the drift region 18. The doping concentration of the buffer region 20 is higher than the doping concentration of the drift region 18. The buffer region 20 may function as a field stop layer that prevents a depletion layer extending from the lower surface side of the base region 14 from reaching the P+ type collector region 22 and the N+ type cathode region 82.

[0066] In the transistor section 70, a P+ type collector region 22 exposed to the lower surface 23 is formed below the buffer region 20. In the diode section 80, an N+ type cathode region 82 exposed to the lower surface 23 is formed below the buffer region 20. In the boundary section 90, either the collector region 22 or the cathode region 82 is formed below the buffer region 20. In the boundary section 90 of this example, the collector region 22 is formed below the buffer region 20. The diode section 80 is a region that overlaps with the cathode region 82 in a direction perpendicular to the lower surface 23. The transistor section 70 is a region where predetermined unit configurations including the emitter region 12 and the contact region 15 are regularly arranged among the region that overlaps with the collector region 22 in a direction perpendicular to the lower surface 23.

[0067] At least one gate trench portion 40 and at least one dummy trench portion 30 are formed on the upper surface 21 side. Each trench portion penetrates the base region 14 from the upper surface 21 to reach the drift region 18. In a region where at least one of the emitter region 12, the contact region 15, the accumulation region 16, and the high concentration region 17 is provided, each trench portion also penetrates these regions to reach the drift region 18. The trench portion penetrating the impurity region is not limited to a case where the trench portion is formed in the order of forming the impurity region and then forming the trench portion. A case where the impurity region is formed between the trench portions after the trench portions are formed is also included in the case where the trench portion penetrates the impurity region.

[0068] The gate trench portion 40 has a gate trench, a gate insulating film 42, and a gate conductive portion 44 formed on the upper surface 21 side. The gate insulating film 42 is formed to cover the inner wall of the gate trench. The gate insulating film 42 may be formed by oxidizing or nitriding the semiconductor on the inner wall of the gate trench. The gate conductive portion 44 is formed inside the gate insulating film 42 inside the gate trench. In other words, the gate insulating film 42 insulates the gate conductive portion 44 from the semiconductor substrate 10. The gate conductive portion 44 is formed of a conductive material such as polysilicon.

[0069] The gate conductive portion 44 includes at least a region facing the adjacent base region 14 in the depth direction. The gate trench portion 40 in this cross section is covered at the upper surface 21 with the interlayer insulating film 38. When a predetermined voltage is applied to the gate conductive portion 44, a channel is formed in the surface layer of the interface of the base region 14 that contacts the gate trench.

[0070] The dummy trench portion 30 may have the same structure as the gate trench portion 40 in the cross section. The dummy trench portion 30 has a dummy trench, a dummy insulating film 32, and a dummy conductive portion 34 formed on the upper surface 21 side. The dummy insulating film 32 is formed to cover the inner wall of the dummy trench. The dummy conductive portion 34 is formed inside the dummy trench and is formed on the inner side of the dummy insulating film 32. The dummy insulating film 32 insulates the dummy conductive portion 34 from the semiconductor substrate 10. The dummy conductive portion 34 may be formed of the same material as the gate conductive portion 44. For example, the dummy conductive portion 34 is formed of a conductive material such as polysilicon. The dummy conductive portion 34 may have the same length as the gate conductive portion 44 in the depth direction. The dummy trench portion 30 in the cross section is covered by an interlayer insulating film 38 on the upper surface 21.

[0071] In this example, a region where the emitter region 12 is formed on the upper surface 21 side, the collector region 22 is formed on the lower surface 23 side, and one or more accumulation regions 16 are formed is defined as a transistor section 70. A region where one or more high concentration regions 17 are formed on the upper surface 21 side, and a cathode region 82 is formed on the lower surface 23 side is defined as a diode section 80. A region between the transistor section 70 and the diode section 80 where the emitter region 12 is not formed on the upper surface 21 side, and the cathode region 82 is not formed on the lower surface 23 of the diode section 80 is defined as a boundary section 90.

[0072] In this specification, the integral concentration refers to the doping concentration integrated in the depth direction of the semiconductor substrate 10. In at least one mesa portion 95 of the transistor portion 70, the integral concentration of one or more accumulation regions 16 (i.e., the integral concentration of an N-type region between the base region 14 and the drift region 18 that has a higher concentration than the drift region 18) may be higher than the integral concentration of one or more high concentration regions 17 in the mesa portion 95 of the diode portion 80 (i.e., the integral concentration of an N-type region between the base region 14 and the drift region 18 that has a higher concentration than the drift region 18).

[0073] Alternatively, the integrated concentration of the accumulation region 16 may be higher than the integrated concentration of the high concentration region 17 of the boundary portion 90. In this case, for example, minority carriers at the time of turn-off are more easily extracted than in the transistor portion 70, and latch-up can be suppressed in the mesa portion 95 of the transistor portion 70, particularly on the diode portion 80 side.

[0074] Alternatively, the integrated concentration of the high concentration region 17 in the boundary portion 90 may be higher than the integrated concentration of the high concentration region 17 in the diode portion 80. In this case, in an operation mode in which a voltage higher than that of the collector electrode 24 is applied to the emitter electrode 52 and the diode portion 80 is conductive, the injection of minority carriers (holes in this example) in the boundary portion 90 can be suppressed more than the injection of minority carriers in the diode portion 80. Alternatively, the integrated concentration of the high concentration region 17 in the boundary portion 90 may be approximately the same as or lower than the integrated concentration of the high concentration region 17 in the diode portion 80.

[0075] The integrated concentration of the accumulation region 16 in the transistor section 70 and the integrated concentration of the high concentration region 17 in the boundary section 90 may be substantially the same. Also, the integrated concentration of the accumulation region 16 in the transistor section 70 and the integrated concentration of the high concentration region 17 in the diode section 80 may be substantially the same.

[0076] In this example, the integrated concentration in each mesa portion 95 of the diode portion 80 is the same. All mesa portions 95 of the diode portion 80 may have the same doping concentration distribution. The integrated concentration in all mesa portions 95 of the transistor portion 70 may be the same as or lower than the integrated concentration in each mesa portion 95 of the diode portion 80. On the other hand, the integrated concentration in all mesa portions 95 of the transistor portion 70 may be higher than the integrated concentration in each mesa portion 95 of the diode portion 80. All mesa portions 95 of the transistor portion 70 may have the same integrated concentration. Also, all mesa portions 95 of the transistor portion 70 may have the same doping concentration distribution.

[0077] By providing the accumulation region 16 or the high concentration region 17 in the transistor section 70 and the diode section 80, when the diode section 80 is operating, the injection of holes from the upper surface 21 side into the drift region 18 can be suppressed. As a result, the reverse recovery characteristics of the semiconductor device 100 can be improved.

[0078] In the boundary portion 90 of this example, a region (high concentration region 17) of the first conductivity type having a higher concentration than the drift region 18 may not be formed between the base region 14 and the drift region 18. Alternatively, the number of high concentration regions 17 in the boundary portion 90 may be smaller or the integrated concentration may be smaller than the accumulation region 16 of the transistor portion 70 and the high concentration region 17 of the diode portion 80. This allows holes in the drift region 18 to be extracted through the boundary portion 90. Therefore, when the transistor portion 70 is turned off, etc., it is possible to suppress the holes in the drift region 18 of the diode portion 80 from flowing to the transistor portion 70. In the examples of FIG. 1 and FIG. 2a, the boundary portion 90 has one mesa portion 95, but the boundary portion 90 may have multiple mesa portions 95.

[0079] Fig. 2b is a diagram showing another example of the d-d' cross section in Fig. 1. The semiconductor device 100 shown in Fig. 2b differs from the semiconductor device 100 shown in Fig. 2a in that a high concentration region 17-1 is provided in the mesa portion 95 of the boundary portion 90 in the semiconductor device 100 shown in Fig. 2a. Fig. 2b shows an example in which one high concentration region 17-1 is provided, but a plurality of high concentration regions 17 may be formed in each mesa portion 95 of the boundary portion 90.

[0080] The number of high concentration regions 17 in the boundary portion 90 may be smaller than the number of accumulation regions 16 in the transistor portion 70. In this case, for example, minority carriers at the time of turn-off are more easily extracted than in the transistor portion 70, and latch-up can be suppressed in the mesa portion 95 of the transistor portion 70, particularly on the diode portion 80 side. Alternatively, the number of high concentration regions 17 in the boundary portion 90 may be the same as or greater than the number of accumulation regions 16 in the transistor portion 70.

[0081] The number of high concentration regions 17 in the boundary portion 90 may be less than or equal to the number of high concentration regions 17 in the diode portion 80. That is, if the number of accumulation regions 16 in the transistor portion 70 is Nt, the number of high concentration regions 17 in the boundary portion 90 is Nk, and the number of high concentration regions 17 in the diode portion 80 is Nd, Nt≧Nd≧Nk may be satisfied. The relationship between Nt, Nk, and Nd may be Nd≧Nt≧Nk. Furthermore, Nt>Nd≧Nk may be satisfied, or Nt≧Nd>Nk may be satisfied, or Nt>Nd>Nk may be satisfied. Alternatively, Nd>Nt≧Nk may be satisfied, or Nd≧Nt>Nk may be satisfied, or Nd>Nt>Nk may be satisfied. In this example, one high concentration region 17-1 is formed as shown in FIG. 2b.

[0082] Fig. 2c is a diagram showing another example of the d-d' cross section in Fig. 1. The semiconductor device 100 shown in Fig. 2c is different from the semiconductor device 100 shown in Fig. 2a in that two high concentration regions 17-1 and 17-2 are provided in the mesa portion 95 of the boundary portion 90 in the semiconductor device 100 shown in Fig. 2a, and one high concentration region 17-1 is provided in the mesa portion 95 of the diode portion. Note that in this example as well, the number of accumulation regions 16 in the transistor portion 70 is three.

[0083] 2c, the number of high concentration regions 17 provided in one mesa portion 95 of the boundary portion 90 may be greater than the number of high concentration regions 17 in the diode portion 80. In this case, in an operation mode in which a voltage higher than that of the collector electrode 24 is applied to the emitter electrode 52 and the diode portion 80 is conductive, the injection of minority carriers (holes in this example) in the boundary portion 90 can be suppressed more than the injection of minority carriers in the diode portion 80.

[0084] The number of accumulation regions 16 in the transistor section 70, the number of high concentration regions 17 in the boundary section 90, and the number of high concentration regions 17 in the diode section 80 may be the same. That is, if the number of accumulation regions 16 in the transistor section 70 is Nt, the number of high concentration regions 17 in the boundary section 90 is Nk, and the number of high concentration regions 17 in the diode section 80 is Nd, Nt≧Nk≧Nd may be satisfied. Furthermore, the relationship between Nt, Nk, and Nd may be Nk≧Nt≧Nd. Furthermore, Nt≧Nk>Nd or Nt>Nk≧Nd may be satisfied. Alternatively, Nk≧Nt>Nd or Nk>Nt≧Nd or Nk>Nt>Nd may be satisfied.

[0085] Furthermore, in the depth direction from the upper surface 21 toward the lower surface 23 of the semiconductor substrate 10, the doping concentration distribution of the accumulation region 16 of the transistor section 70, the doping concentration distribution of the high concentration region 17 of the boundary section 90, and the doping concentration distribution of the high concentration region 17 of the diode section 80 may be substantially the same. In this case, the accumulation region 16 of the transistor section 70, the high concentration region 17 of the boundary section 90, and the high concentration region 17 of the diode section 80 may all be formed by the same ion implantation and annealing treatment, or may be formed in different processes.

[0086] Fig. 2d is a diagram showing another example of the d-d' cross section in Fig. 1. The semiconductor device 100 shown in Fig. 2d differs from the semiconductor device 100 shown in Fig. 2a in that a crystal defect layer 89 is provided in the drift region 18 at a depth position closer to the upper surface 21 than the middle position in the depth direction of the semiconductor substrate 10 in the semiconductor device 10 shown in Fig. 2a, from a region adjacent to the boundary portion 90 of the transistor portion 70 to the diode portion 80 in the Y-axis direction. As an example, the crystal defect layer 89 may be formed by locally injecting a lifetime killer such as helium.

[0087] The crystal defect layer 89 is a layer including crystal defects. The crystal defects may be any defects that become recombination centers, and may be, for example, vacancies, complex vacancies, dislocations, interstitial atoms, helium atoms, metal atoms, or the like. This also improves the reverse recovery characteristics. The crystal defect layer 89 may be formed in the diode portion 80 and the boundary portion 90 in the arrangement direction (Y-axis direction) of the trench portions, and may further extend to include one or more predetermined mesa portions 95 of the transistor portion. In addition, the crystal defect layer 89 may be disposed so as to cover the entire dummy trench portion 30 in the extension direction (X-axis direction) of the trench portions, in a top view, so as to include at least the end of the dummy trench portion 30 in the extension direction.

[0088] Fig. 2e is a diagram showing the concentration distribution of the crystal defect layer 89 in the n-n' cross section of Fig. 2d. As shown in Fig. 2e, the crystal defect layer 89 may be in the drift region 18 at a depth position where the position of the peak concentration Pe of the crystal defects is closer to the upper surface 21 than the middle position in the depth direction of the semiconductor substrate 10. That is, a part of the region of the crystal defect layer 89 on the lower surface 23 side in the depth direction from the position of the peak concentration Pe of the crystal defects may be distributed on the lower surface 23 side of the middle position in the depth direction of the semiconductor substrate 10.

[0089] The crystal defect concentration distribution of the crystal defect layer 89 in the diode section 80 may be a distribution that tails from the upper surface 21 to the position of the peak concentration Pe. In this case, the crystal defect concentration distribution does not have to reach the lower surface 23. As long as the distribution tails from the upper surface 21 to the position of the peak concentration Pe, the depth position of the peak concentration Pe may be closer to the lower surface 23 than the middle position in the depth direction of the semiconductor substrate 10. In this example, the depth position of the peak concentration Pe is inside the crystal defect layer 89.

[0090] FIG. 2f is a diagram showing an example of a cross section of a semiconductor device 150 according to an embodiment of the present invention. The semiconductor device 150 shown in FIG. 2f differs from the semiconductor device 100 shown in FIG. 2a in that a plurality of mesa portions 95 are provided at the boundary portion 90. The semiconductor device 150 also differs from the semiconductor device 100 shown in FIG. 2a in that a crystal defect layer 89 is provided in the drift region 18 at a depth position closer to the upper surface 21 than the middle position in the depth direction of the semiconductor substrate 10, from a region adjacent to the boundary portion 90 of the transistor portion 70 to the diode portion 80 in the Y-axis direction. The crystal defect layer 89 may be a vacancy, a divacancy, a dislocation, an interstitial atom, a helium atom, or the like, as in the example of FIG. 2d.

[0091] In the semiconductor device 150 of the present example, the mesa portion 95 of the boundary portion 90 adjacent to the diode portion 80 is provided with a greater number of high concentration regions 17 than the number of high concentration regions 17 in the diode portion 80. Moreover, in the semiconductor device 150 of the present example, the mesa portion 95 of the boundary portion 90 adjacent to the transistor portion 70 is not provided with high concentration regions 17.

[0092] In addition, among the mesa portions 95 of the boundary portion 90, the mesa portion 95 sandwiched between the mesa portion 95 adjacent to the diode portion 80 and the mesa portion 95 adjacent to the transistor portion 70 may be provided with a greater number of high concentration regions 17 than the number of high concentration regions 17 provided in the mesa portion 95 adjacent to the diode portion 80, or may be provided with a smaller number of high concentration regions 17, or may not be provided with any high concentration regions 17.

[0093] According to the semiconductor device 150 of this embodiment, for example, minority carriers at the time of turn-off can be more easily extracted than in the transistor section 70. Therefore, latch-up in the mesa section 95 of the transistor section 70, particularly on the diode section 80 side, can be suppressed.

[0094] Furthermore, according to the semiconductor device 150 of the present example, the mesa portion 95 of the boundary portion 90 adjacent to the diode portion 80 has a greater number of high concentration regions 17 than the number of high concentration regions 17 in the diode portion 80. Therefore, as in the example shown in FIG. 2c, in an operating mode in which a voltage higher than that of the collector electrode 24 is applied to the emitter electrode 52 and the diode portion 80 is conductive, the injection of minority carriers (holes in this example) in the boundary portion 90 can be suppressed more than the injection of minority carriers in the diode portion 80.

[0095] 2g is a diagram showing another example of a cross section of the semiconductor device 150 according to the embodiment of the present invention. The semiconductor device 150 shown in FIG. 2g differs from the semiconductor device 150 shown in FIG. 2f in that one high-concentration region 17-1 is provided in the mesa portion 95 of the boundary portion 90 adjacent to the transistor portion 70. As a result, when the diode portion 80 is in a conductive operation mode, the injection of minority carriers (holes in this example) from the mesa portion 95 can be suppressed more than the injection of minority carriers from the diode portion 80.

[0096] 2g, the mesa portion 95 of the boundary portion 90 adjacent to the transistor portion 70 may be provided with a smaller number of high concentration regions 17 than the number of accumulation regions 16 provided in the transistor portion 70. In this case, for example, minority carriers at the time of turn-off can be more easily extracted than in the transistor portion 70, and latch-up in the mesa portion 95 of the transistor portion 70, particularly on the diode portion 80 side, can be suppressed.

[0097] 2f and 2g, it is sufficient that Nkd≧Nd or Nt≧Nkt. In addition, the relationship between Nkt and Nkd may be satisfied.

[0098] On the other hand, when a lifetime killer is injected, the trade-off between on-voltage and off-loss in the transistor section 70 may worsen. In this example, since no lifetime killer is used or the amount of the lifetime killer can be reduced, the reverse recovery characteristics can be improved while suppressing the deterioration of the on-voltage-off-loss characteristics. Also, the characteristic variation and leakage current caused by the lifetime killer can be suppressed. Also, by using a resist mask that is cheaper in unit price than a metal mask for injecting a lifetime killer, the manufacturing cost can be reduced.

[0099] If the integral concentration of the high concentration region 17 in the diode section 80 becomes too high, the trade-off between the switching loss during reverse recovery and the on-loss for the forward voltage in the diode section 80 may deteriorate. In response to this, the deterioration of the trade-off can be suppressed by making the integral concentration of the high concentration region 17 in the diode section 80 lower than the integral concentration of the accumulation region 16 in the transistor section 70. The integral concentration in the diode section 80 may be 70% or less of the integral concentration in the transistor section 70, or may be 50% or less.

[0100] 3 is a diagram showing an example of the doping concentration distribution at the ee' cross section and the f-f' cross section of FIG. 2a. The ee' cross section is a cross section of the mesa portion 95 of the transistor portion 70, and the f-f' cross section is a cross section of the mesa portion 95 of the diode portion 80.

[0101] In each of the accumulation regions 16 and high concentration regions 17, the doping concentration distribution in the depth direction of the semiconductor substrate 10 has one peak. When a plurality of accumulation regions 16 or high concentration regions 17 are formed in the depth direction of the semiconductor substrate 10, the accumulation regions 16 and high concentration regions 17 have a plurality of peaks (maximum values) in the doping concentration distribution in the depth direction and minimum values ​​at positions sandwiched between the plurality of peaks in the depth direction. In other words, a region between the plurality of minimum values ​​may be one accumulation region 16 or one high concentration region 17. Each of the accumulation regions 16 and high concentration regions 17 may be formed by injecting impurities from the upper surface 21 or the lower surface 23.

[0102] FIG. 3 shows the doping concentration distribution from the emitter region 12 to the top end of the drift region 18. As in FIG. 3, the vertical axis of the graph showing the impurity concentration is a logarithmic axis. Each scale mark on the vertical axis indicates 10 times. In this specification, the doping concentration refers to the concentration of the impurity that has become a donor or an acceptor. The doping concentration shown in FIG. 3 corresponds to the concentration difference between the donor and the acceptor.

[0103] Each mesa portion 95 of the transistor portion 70 of this example has a plurality of accumulation regions 16. In the example of Fig. 3, the transistor portion 70 has a first accumulation region 16-1, a second accumulation region 16-2, and a third accumulation region 16-3. The doping concentration of the first accumulation region 16-1 is D1, the doping concentration of the second accumulation region 16-2 is D2, and the doping concentration of the third accumulation region 16-3 is D3. The doping concentration values ​​may be peak values.

[0104] Moreover, the doping concentration Dv at the boundary of each accumulation region 16 is a minimum value of the doping concentration distribution of the accumulation region 16. The doping concentration Dv is greater than the doping concentration Dd of the drift region 18. The doping concentration Dv may be 1 / 10 or less, or may be 1 / 100 or less, of the doping concentration D1.

[0105] In the multiple accumulation regions 16, there may be multiple boundaries between the accumulation regions 16. There may also be multiple minimum values ​​(Dv) of the doping concentration at the boundaries between the accumulation regions 16. The multiple minimum values ​​(Dv) of the doping concentration may be different values. In this example, the two doping concentrations Dv are approximately the same value.

[0106] Each mesa 95 of the diode section 80 in this example has a plurality of high concentration regions 17. However, the number of high concentration regions 17 formed in the depth direction in each mesa 95 of the diode section 80 may be less than the number of accumulation regions 16 formed in the depth direction in each mesa 95 of the transistor section 70. This makes it easy to make the integral concentration of one or more high concentration regions 17 in each mesa 95 of the diode section 80 smaller than the integral concentration of one or more accumulation regions 16 in each mesa 95 of the transistor section 70. In the example of FIG. 3, the diode section 80 has a first high concentration region 17-1 and a second high concentration region 17-2. The doping concentration of the first high concentration region 17-1 is D4, and the doping concentration of the second high concentration region 17-2 is D5.

[0107] Each high concentration region 17 of the diode section 80 may be provided at the same depth position as any one of the accumulation regions 16 of the transistor section 70. The depth position of each region may be the position where the doping concentration distribution in the region is at a peak. In this example, the first high concentration region 17-1 is formed at the same depth position as the first accumulation region 16-1, and the second high concentration region 17-2 is formed at the same depth position as the second accumulation region 16-2. The same depth position may have a predetermined error. For example, even if the position of the peak has an error of 10% or less of the half-width of the mountain-shaped doping concentration distribution including the peak, the same depth position can be obtained. By forming each region at the same depth position, it is easy to simplify the manufacturing process.

[0108] Moreover, the doping concentration of each high concentration region 17 of the diode section 80 may be equal to the doping concentration of the accumulation region 16 provided at the same depth in the transistor section 70. Here, the doping concentration may be the peak value of the doping concentration in the region. In this example, the doping concentration D4 of the first high concentration region 17-1 is equal to the doping concentration D1 of the first accumulation region 16-1. Moreover, the doping concentration D5 of the second high concentration region 17-2 is equal to the doping concentration D2 of the second accumulation region 16-2. The doping concentrations being equal may have a predetermined error. For example, even if the doping concentration has an error of 10% or less, it can be the same doping concentration. Moreover, the doping concentration Dv at the boundary between the two high concentration regions 17 may be equal to the doping concentration Dv at the boundary between the two accumulation regions 16.

[0109] In this way, by making the depth position and doping concentration of each of the high concentration regions 17 the same as those of any of the accumulation regions 16, the high concentration regions 17 can be formed in the same manufacturing process as the accumulation region 16. This makes it possible to simplify the manufacturing process.

[0110] The doping concentration of any one of the multiple accumulation regions 16 in each mesa portion 95 of the transistor portion 70 may be higher than the doping concentrations of the other accumulation regions 16 formed at different depth positions. In the transistor portion 70 of this example, the doping concentration D3 of the third accumulation region 16-3 provided at the deepest position is higher than the doping concentrations (D1, D2) of any of the other accumulation regions 16 in the transistor portion 70. The doping concentration D3 may be about three times or more and seven times or less than the doping concentration D1. The doping concentrations D1 and D2 may be the same.

[0111] In addition, in the multiple accumulation regions 16 in each mesa portion 95 of the transistor section 70, the multiple doping concentrations Dv may decrease with increasing depth from the upper surface 21. The doping concentration Dv corresponds to a valley of the doping concentration distribution with respect to the peak concentrations D1, D2, and D3. By decreasing the concentration of the valleys of the multiple doping concentrations in the depth direction, the capacitance between the gate and collector can be adjusted to a predetermined value.

[0112] The diode section 80 does not need to have a high concentration region 17 corresponding to the region with the highest doping concentration among the accumulation regions 16 of the transistor section 70. This allows the integrated concentration of the high concentration region 17 of the diode section 80 to be sufficiently lower than the integrated concentration of the accumulation region 16 in the transistor section 70. In this example, the diode section 80 does not have a high concentration region 17 at the same depth as the third accumulation region 16-3 provided at the deepest position in the transistor section 70.

[0113] When three or more high concentration regions 17 are formed in the diode portion 80, the doping concentrations Dv may decrease with increasing depth from the upper surface 21. When three or more high concentration regions 17 are formed in the boundary portion 90, the doping concentrations Dv may decrease with increasing depth from the upper surface 21.

[0114] As an example, the peak positions of the doping concentration of each accumulation region 16 are arranged at equal intervals in the depth direction. As another example, the peak positions of the doping concentration of each accumulation region 16 may be arranged at unequal intervals in the depth direction. By providing a plurality of accumulation regions 16 in the transistor section 70, it is possible to increase the transient capacitance between the gate conductive section 44 and the collector electrode 24 at the time of turn-on. This makes it possible to reduce the turn-on loss while improving the trade-off between the on-voltage and the turn-off loss in the transistor section 70.

[0115] FIG. 4 is a diagram showing an example of the waveform of the collector current Ic at the time of turn-on. Waveform 93 shows the collector current Ic when the accumulation region 16 is not provided. Waveform 94 shows the collector current Ic when the first accumulation region 16-1 is provided. The first accumulation region 16-1 is provided near the base region 14, so it increases the negative capacitance between the gate and the collector. Therefore, the di / dt of the collector current Ic at the time of turn-on increases. By providing the first accumulation region 16-1, it is possible to improve the trade-off between the on-voltage and the turn-off loss, but since the di / dt at the time of turn-on increases, if the gate resistance is increased to suppress the increase in di / dt, the turn-on loss increases.

[0116] Waveform 91 shows the collector current Ic when the first accumulation region 16-1 and the third accumulation region 16-3 are provided. The third accumulation region 16-3 is provided at a position away from the base region 14, which increases the capacitance between the gate and the collector. This reduces the di / dt of the collector current Ic at turn-on. This makes it possible to reduce turn-on loss while improving the trade-off between the on-voltage and turn-off loss.

[0117] Waveform 92 shows the collector current Ic when the first accumulation region 16-1, the second accumulation region 16-2, and the third accumulation region 16-3 are provided. By providing the second accumulation region 16-2, the capacitance between the gate and the collector is further increased. Therefore, it is possible to further reduce the turn-on loss while improving the trade-off between the on-voltage and the turn-off loss.

[0118] 5 is a diagram showing another example of the doping concentration distribution in the ee' and ff' cross sections of FIG. 2a. In this example, the doping concentration distribution in the transistor section 70 is the same as the example in FIG.

[0119] The diode section 80 of this example has one high concentration region 17 in each mesa section 95. That is, between the base region 14 and the drift region 18, the N-type doping concentration distribution higher than that of the drift region 18 has one peak. The high concentration region 17 of this example may be formed in a range longer in the depth direction than any of the accumulation regions 16. The doping concentration D6 of the high concentration region 17 is set so that the integral concentration of the high concentration region 17 is lower than the integral concentration of one or more accumulation regions 16 in the transistor section 70. The doping concentration D6 of the high concentration region 17 may be lower or higher than the doping concentration D1 of the first accumulation region 16.

[0120] This configuration also makes it possible to improve the reverse recovery characteristics while suppressing deterioration of the on-voltage-off-loss characteristics in the transistor section 70. It also makes it possible to suppress deterioration of the trade-off between the switching loss during reverse recovery and the on-loss with respect to the forward voltage in the diode section 80.

[0121] 6 is a diagram showing the electron current and the displacement current at the time of turn-on in a case where a first accumulation region 16-1, a second accumulation region 16-2, and a third accumulation region 16-3 are provided in a certain mesa portion 95 of the transistor portion 70 and in the gate trench portion 40 and the dummy trench portion 30 in contact with the mesa portion 95. Electrons that have passed through the channel travel in the arrangement direction (X-axis direction) in the first accumulation region 16-1. However, in this example, the second accumulation region 16-2 and the third accumulation region 16-3 are provided below the first accumulation region 16-1.

[0122] In this example, the impedance for the electron current is lower in the path that flows directly from the first accumulation region 16-1 to the second accumulation region 16-2 than in the path that flows from near the center of the first accumulation region 16-1 back to near the gate trench portion 40 to the second accumulation region 16-2. Similarly, the impedance for the electron current is lower in the path that flows directly from the second accumulation region 16-2 to the third accumulation region 16-3 than in the path that flows from near the center of the second accumulation region 16-2 back to near the gate trench portion 40 to the third accumulation region 16-3.

[0123] Of the areas below each accumulation region 16, holes are likely to accumulate in the high hole concentration region 87 adjacent to the gate trench portion 40. In addition, the electron current flows near the center of the mesa portion 95 rather than near the gate trench portion 40, which promotes the accumulation of holes in the high hole concentration region 87. This promotes the flow of the electron current near the center of the mesa portion 95. Although FIG. 6 shows the high hole concentration region 87 in which holes are accumulated, the high hole concentration region 87 may exist only near the boundary between the gate trench portion 40 and the semiconductor substrate 10.

[0124] As described above, the electron current in this example does not return to the vicinity of the gate trench portion 40, but travels downward near the center of the mesa portion 95 sandwiched between the gate trench portion 40 and the dummy trench portion 30. That is, the electron current in this example flows near the center of the mesa portion 95, not near the gate trench portion 40. The effect of the electron current flowing near the center of the mesa portion 95 is produced by arranging the multiple accumulation regions 16-1 to 16-3 in the depth direction.

[0125] When the electron current flows near the center of the mesa portion 95, the hole distribution near the bottom of the mesa portion 95 is divided near the center of the mesa portion 95. Therefore, the holes on the dummy trench portion 30 side of the electron current path do not flow to the gate trench portion 40 side. This division of the hole distribution at the center of the mesa portion 95 suppresses the accumulation of holes at the bottom end of the gate trench portion 40. As a result, the displacement current can be reduced. Since the displacement current can be reduced, the charging of the gate conductive portion 44 is also reduced, and the instantaneous increase of the gate electrode Vge is also suppressed. This also suppresses the voltage reduction rate (dV / dt) between the collector electrode 24 and the emitter electrode 52. 6 is considered to be caused by the hole distribution being divided by the electron current between the gate trench portion 40 and the dummy trench portion 30. In addition, due to the hole distribution, the displacement current flowing from the vicinity of the bottom end of the dummy trench portion 30 to the vicinity of the bottom end of the gate trench portion 40 can be reduced when the device is turned on.

[0126] The second accumulation region 16-2 and the third accumulation region 16-3 may not be in contact with the dummy trench portion 30. In this case, the holes can exist from the lower end of the dummy trench portion 30 to immediately below the first accumulation region 16-1 on the side of the dummy trench portion 30. This can facilitate the extraction of the holes to the emitter electrode 52 at the time of turn-off.

[0127] Fig. 7a is a diagram showing another example of the dd' cross section in Fig. 1. In this example, the structures of the diode section 80 and the boundary section 90 are the same as those in any of the examples shown in Figs.

[0128] In the mesa portions 95 of the transistor portion 70 in this example, the integral concentration of one or more accumulation regions 16 in the mesa portion 95-1 provided closest to the diode portion 80 is lower than the integral concentration of one or more accumulation regions 16 in other mesa portions 95 (e.g., mesa portion 95-2) of the transistor portion 70. This makes it possible to make the change in integral concentration between adjacent mesa portions 95 gentler, and to suppress concentration of an electric field, current, or the like. In the mesa portions 95 of the transistor portion 70 on the diode portion 80 side, the integral concentration may decrease the closer to the diode portion 80.

[0129] Furthermore, the integrated concentration of one or more accumulation regions 16 in the mesa portion 95-1 may be higher than the integrated concentration of one or more high concentration regions 17 in the mesa portion 95-3 of the diode portion 80. By making the integrated concentration in the mesa portion 95-1 at the end of the transistor portion 70 higher than the integrated concentration in the mesa portion 95-3 of the diode portion 80, injection of holes from the transistor portion 70 to the diode portion 80 can be suppressed.

[0130] 7B is a diagram showing an example of doping concentration distributions in the e-e', f-f', and g-g' cross sections in FIG. 7A. The e-e' cross section is a cross section in mesa portion 95-2, the f-f' cross section is a cross section in mesa portion 95-3, and the g-g' cross section is a cross section in mesa portion 95-1.

[0131] In this example, the number of accumulation regions 16 in a mesa portion 95-1 at the end of the transistor portion 70 is smaller than the number of accumulation regions 16 in another mesa portion 95-2 of the transistor portion 70. Also, the number of high concentration regions 17 in the diode portion 80 is smaller than the number of accumulation regions 16 in the mesa portion 95-1. With this configuration, the integral concentration in each mesa portion 95 can be easily adjusted.

[0132] In this example, each accumulation region 16 in the mesa portion 95-1 is provided at the same depth position as any one of the accumulation regions 16 in the mesa portion 95-2. The doping concentration of the accumulation regions 16 formed at the same depth is the same. In the example of FIG. 7b, the mesa portion 95-1 does not have an accumulation region 16 corresponding to the third accumulation region 16-3 having the highest doping concentration among the accumulation regions 16 provided in the mesa portion 95-2. In another example, the mesa portion 95-1 may have an accumulation region 16 corresponding to the third accumulation region 16-3 having the highest doping concentration. In this case, the mesa portion 95-1 does not have an accumulation region 16 corresponding to the first accumulation region 16-1 or the second accumulation region 16-2.

[0133] The high concentration region 17 in the mesa portion 95-3 is provided at the same depth as any one of the accumulation regions 16 in the mesa portion 95-1. In this example, it is provided at the same depth as the first accumulation region 16-1.

[0134] In the mesa portion 95-1, the mesa portion 95-2, and the mesa portion 95-3, the high-concentration N-type regions formed at the same depth position may have the same doping concentration. In the example of FIG. 7b, D1=D6=D8, and D2=D7. With such a configuration, the manufacturing process can be simplified.

[0135] The doping concentration distribution of the high-concentration N-type region in each mesa portion 95 is not limited to the example shown in Fig. 7b. For example, one high-concentration N-type region may be formed in each of mesa portion 95-1 and mesa portion 95-3. In this case, the doping concentration of the high-concentration N-type region in mesa portion 95-1 is higher than the doping concentration of the high-concentration N-type region in mesa portion 95-3.

[0136] 8 is a diagram showing another example of the d-d' cross section in FIG. 1. The semiconductor device 100 of this example further includes a floating region 84 in addition to the configuration of any one of the semiconductor device 100 described in FIG. 2a to FIG. 7b. The floating region 84 is provided on the lower surface 23 side of the diode section 80. In this example, the lower surface 23 side refers to the region between the center in the depth direction of the semiconductor substrate 10 and the upper end of the cathode region 82. The floating region 84 of this example is formed in contact with the upper end of the cathode region 82.

[0137] The floating region 84 is a region of the second conductivity type (P+ in this example) that is in an electrically floating state. An electrically floating state refers to a state in which the region is not electrically connected to either the collector electrode 24 or the emitter electrode 52. By providing the floating region 84, it is possible to suppress the injection of electrons from the cathode region 82. This makes it possible to adjust the carrier distribution in the depth direction of the semiconductor substrate 10 without forming a lifetime killer on the back surface side of the semiconductor substrate 10. This makes it possible to reduce costs and also to reduce the leakage current caused by the lifetime killer.

[0138] The floating region 84 is formed so as to partially cover the cathode region 82. In other words, a portion of the cathode region 82 is not covered by the floating region 84. This allows the diode section 80 to operate as a diode even if the floating region 84 is provided. In order to suppress the injection of electrons, the floating region 84 may be formed so as to cover an area larger than half of the upper surface of the cathode region 82.

[0139] Fig. 9 is a cross-sectional view for explaining an example of the arrangement of the floating region 84. Fig. 9 shows an enlarged view of the vicinity of the floating region 84. Note that the collector electrode 24 is omitted in Fig. 9. Note that while the boundary portion 90 is provided adjacent to the diode portion 80 in Fig. 9, in other examples, the transistor portion 70 may be provided adjacent to the diode portion 80.

[0140] In this example, P1 is the boundary position between collector region 22 and cathode region 82 in a plane parallel to lower surface 23. In Fig. 9, P1 is the boundary position in a cross section parallel to the dd' cross section. As an example, the dd' cross section is a plane that is perpendicular to lower surface 23 and parallel to the arrangement direction of each trench portion.

[0141] Moreover, in a plane parallel to the lower surface 23, the end position of the floating region 84 is defined as P2. The end position P2 is the end position of the floating region 84 that is closest to the boundary position P1. In the plane parallel to the lower surface 23, the distance from the boundary position P1 to the end position P2 is defined as L1. The distance L1 may be the distance L1 in a cross section parallel to the d-d' cross section.

[0142] Furthermore, the width of floating region 84 is defined as L2 in a plane parallel to lower surface 23. Width L2 of floating region 84 is the width of floating region 84 in the direction of a straight line connecting boundary position P1 and end position P2. The straight line direction may be parallel to the arrangement direction of the trench portions.

[0143] In this example, the distance L1 from the boundary position P1 to the end position P2 is smaller than the width L2 of the floating region 84. The distance L1 may be equal to or smaller than half of the width L2, or may be equal to or smaller than ¼ of the width L2. The distance L1 may be greater than 0. In other words, the floating region 84 does not have to be connected to the collector region 22. In another example, the floating region 84 may be formed up to above the collector region 22.

[0144] When multiple floating regions 84 are provided in the cross section, the width L2 of the floating region 84 may be the average value of the widths of the multiple floating regions 84. By reducing the distance L1, injection of electrons from the cathode region 82 at the end of the diode section 80 can be suppressed.

[0145] The diode section 80 also has an opening region 85 where no floating region 84 is provided at the same depth position as the floating region 84. The opening region 85 may refer to a region sandwiched between the floating regions 84. As an example, the opening region 85 is an N-type region. The doping concentration of the opening region 85 may be the same as the doping concentration of the drift region 18 or the buffer region 20. The opening region 85 may be the drift region 18 or the buffer region 20 remaining without the floating region 84 being formed.

[0146] In this example, the width of the opening region 85 in the linear direction described above is L3. The distance L1 from the boundary position P1 to the end position P2 may be smaller than the width L3 of the opening region 85. The distance L1 may be half or less of the width L3, or may be one-quarter or less. Moreover, the width L2 may be two or more times the width L3, three or more times the width L3, or five or more times the width L3.

[0147] When a plurality of opening regions 85 are provided in the cross section, the width L3 of the opening region 85 may be the average value of the widths of the plurality of opening regions 85. By reducing the distance L1, the injection of electrons from the cathode region 82 at the end of the diode portion 80 can be suppressed.

[0148] The length of the floating region 84 in the depth direction is defined as L4. The depth direction refers to the direction perpendicular to the lower surface 23. The distance L1 from the boundary position P1 to the end position P2 may be greater than the length L4 of the floating region 84 in the depth direction. The distance L1 may be twice or more the length L4, or may be three times or more. L4 may be 1 μm or less, or may be 0.75 μm or less. The doping concentration distribution of the floating region 84 in at least one of the depth direction of the semiconductor substrate 10 and the direction parallel to the lower surface 23 may be a Gaussian distribution or a distribution close to it. The peak concentration of the floating region 84 is 5×10 16 / cm 3 That's it, 1×10 18 / cm 3 or less, in this example 3×10 17 / cm 3 It is.

[0149] 10 is a top view showing an example of the arrangement of the floating region 84 in the diode section 80 when projected from the lower surface 23 side of the semiconductor substrate 10 onto the upper surface 21 of the semiconductor substrate 10. The floating region 84 is arranged in a region in which the dummy trench section 30 is provided on the upper surface 21 of the semiconductor substrate 10. The floating region 84 in this example is arranged in the X-axis direction to a position beyond the end position of the longitudinal direction (extension direction) of the dummy trench section 30 or the position of the connection section 25 where the dummy trench section 30 is electrically connected to the emitter electrode 52. The floating region 84 in this example does not reach a position overlapping with the gate runner 48 or the gate metal layer 50. The end of the floating region 84 in the extension direction of the trench section may be provided at a position overlapping with the well region 11.

[0150] The cathode region 82 in this example is located on the inside (in the +X-axis direction) of the contact region 15 formed at the end of the contact hole 54. The end of the floating region 84 in the extension direction of the dummy trench portion 30 is located on the outer periphery side (in the -X-axis direction) of the end of the contact hole 54 in the X-axis direction.

[0151] Fig. 11 is a top view showing an example of the arrangement of the floating region 84 in the diode section 80. Fig. 10 shows a part of the diode section 80, but Fig. 11 shows the entire region in which the dummy trench section 30 is provided in the diode section 80. The diode section 80 may be a region in which the cathode region 82 is formed.

[0152] In this example, a plurality of floating regions 84 are discretely arranged on the upper surface of the semiconductor substrate 10. An opening region 85 is arranged between each of the floating regions 84. Each of the opening regions 85 may be connected to each other. On the upper surface of the semiconductor substrate 10, the area ratio of the floating regions 84 to the total area of ​​the floating regions 84 and the opening regions 85 may be 80% or more, 90% or more, or even 95% or more. The distance L2 of the floating regions 84 may be 5 μm or more and 1000 μm or less, and is 720 μm in this example. The distance L3 of the opening regions 85 between adjacent floating regions 84 may be 1 μm or more and 200 μm or less, and is 180 μm in this example.

[0153] 12 is a top view showing another example of the arrangement of the floating region 84 in the diode section 80. In this example, a plurality of opening regions 85 are discretely arranged on the upper surface of the semiconductor substrate 10. A floating region 84 is arranged between each of the opening regions 85. The floating regions 84 may be connected to each other. The diode section 80 may be a region in which a cathode region 82 is formed.

[0154] On the upper surface of the semiconductor substrate 10, the area ratio of the floating regions 84 to the total area of ​​the floating regions 84 and the opening regions 85 may be 80% or more, 90% or more, or even 95% or more. The distance L2 of the floating regions 84 may be 5 μm or more and 1000 μm or less, and is 720 μm in this example. The distance L3 of the opening regions 85 between adjacent floating regions 84 may be 1 μm or more and 200 μm or less, and is 180 μm in this example.

[0155] 13 is a diagram showing another example of the d-d' cross section in FIG. The semiconductor device 100 of this example further includes a dummy region 86 of a second conductivity type (P+ in this example) in addition to the configuration of any one of the semiconductor devices 100 shown in FIGS. 2a to 7b. The dummy region 86 and the cathode region 82 are provided so as to be exposed alternately on the lower surface 23 of the diode section 80. The dummy region 86 may be electrically connected to the collector electrode 24.

[0156] This configuration also makes it possible to suppress the injection of electrons from the cathode region 82. The area of ​​the lower surface 23 where the dummy region 86 is formed may be larger than the area where the cathode region 82 is formed.

[0157] Fig. 14 is a diagram showing another example of the d-d' cross section in Fig. 1. The semiconductor device 100 of this example further includes a lifetime killer 88 in addition to the configuration of any of the semiconductor device 100 shown in Fig. 2a to Fig. 7b. The lifetime killer 88 is formed on the lower surface 23 side. In this example, the lower surface 23 side refers to the region between the center in the depth direction of the semiconductor substrate 10 and the lower surface 23.

[0158] Furthermore, the lifetime killer 88 is formed locally in the depth direction of the semiconductor substrate 10. That is, the region in which the lifetime killer 88 is formed has a higher defect density than other regions of the semiconductor substrate 10. The lifetime killer 88 in this example is helium implanted at a predetermined depth. By injecting helium, crystal defects can be formed inside the semiconductor substrate 10. The lifetime killer 88 may be formed over the entire surfaces of the transistor portion 70, the diode portion 80 and the boundary portion 90.

[0159] It is not necessary to provide a localized lifetime killer on the upper surface 21 side. In this example, the upper surface 21 side refers to the region between the center in the depth direction of the semiconductor substrate 10 and the bottom position of the trench portion. In this example, no region with a locally high helium concentration (or crystal defect density) is formed on the upper surface 21 side.

[0160] As described above, the semiconductor device 100 has a high concentration N-type region in each mesa portion 95 of the transistor portion 70 and the diode portion 80, so that a crystal defect layer due to a lifetime killer is not formed on the upper surface 21 side, or the crystal defect density of the crystal defect layer can be reduced, so that the injection efficiency of minority carriers in the diode portion 80 can be adjusted. This makes it possible to reduce the cost of forming the lifetime killer, and also to suppress leakage currents and the like caused by the lifetime killer.

[0161] It is not necessary for a local lifetime killer to be formed on the lower surface 23. In this case, it is preferable for the lower surface 23 to have a structure as shown in Fig. 8 or 13. This can further reduce the cost of forming the lifetime killer and can further suppress leakage current and the like caused by the lifetime killer.

[0162] 15 is a diagram showing another example of the arrangement of the lifetime killer 88. The diode section 80 of this example is provided with a floating region 84 and an opening region 85. In this example, the lifetime killer 88 is provided in at least a part of the region above the floating region 84, and the lifetime killer 88 is not provided in at least a part of the region above the opening region 85. This makes it possible to adjust the lifetime of carriers injected from the floating region 84. Also, above the opening region 85, the density of defects caused by the injection of the lifetime killer can be reduced.

[0163] The lifetime killer 88 may be provided over the entire area above the floating region 84. Moreover, the lifetime killer 88 does not have to be provided over the entire area above the opening region 85.

[0164] The semiconductor device 100 of this example has multiple buffer regions 20 at different positions in the depth direction. The multiple buffer regions 20 can be formed by injecting impurities such as protons multiple times with different ranges. Figure 15 shows the peak positions of the doping concentration in the depth direction of each buffer region 20. The doping concentration between each buffer region 20 may be higher than the doping concentration of the drift region 18.

[0165] 15, the peak position of the concentration of the lifetime killer 88 in the depth direction is indicated by a cross. The peak position of the lifetime killer 88 is preferably different from the peak position of the buffer region 20. This makes it possible to prevent defects in the lifetime killer 88 from being terminated by protons in the buffer region 20. The peak position of the concentration of the lifetime killer 88 may be located between the peak positions of the doping concentrations of the two buffer regions 20.

[0166] 16 is a diagram showing an example of the configuration of the diode section 80. In the diode section 80 of this example, two or more high concentration regions 17 are provided in each mesa section 95. As an example, two high concentration regions 17 may be provided in each mesa section 95.

[0167] In addition, the structure on the lower surface 23 side may be the same as any of the diode sections 80 shown in Figures 1 to 15. The diode section 80 in the example of Figure 16 has a floating region 84 and an opening region 85, similar to the example shown in Figure 8.

[0168] 1 to 15, the semiconductor device 100 is described as including the transistor portion 70, the boundary portion 90, and the diode portion 80. In another example, the semiconductor device 100 may include only the diode portion 80.

[0169] 17 is a diagram showing another example of the configuration of the diode section 80. The diode section 80 of this example is the same as the diode section 80 shown in FIG. 16 except for the arrangement of the high concentration region 17. In this example, the integrated concentration of the high concentration region 17 in at least one of the mesa sections 95 arranged above the floating region 84 is lower than the integrated concentration of the high concentration region 17 in at least one of the mesa sections 95 arranged above the opening region 85. As an example, the mesa section 95 whose entirety is arranged above the floating region 84 has a lower integrated concentration of the high concentration region 17 than the mesa section 95 whose entirety is arranged above the opening region 85.

[0170] 17, the number of high concentration regions 17 arranged in the depth direction in mesa portion 95 arranged above floating region 84 is smaller than the number of high concentration regions arranged in the depth direction in mesa portion 95 arranged above opening region 85. With this structure, it is possible to reduce the difference in diode characteristics between the portion where floating region 84 is provided and the portion where opening region 85 is provided.

[0171] Fig. 18 is a diagram showing another example of the semiconductor device 100. The semiconductor device 100 of this example has a floating region 84, and does not have an accumulation region 16 or a high concentration region 17. The other structures are the same as those of the semiconductor device 100 shown in Figs. 1 to 17. Note that a localized lifetime killer may or may not be provided on at least one of the upper surface 21 side and the lower surface 23 side. Also, the boundary portion 90 may not be provided.

[0172] Fig. 19 is a diagram partially illustrating the upper surface of a semiconductor device 200 according to another embodiment of the present invention. The semiconductor device 200 of this example differs from the semiconductor device 100 shown in Fig. 1 in that the base region 14 and the contact region 15 on the upper surface of the diode section 80 are provided alternately adjacent to each other so as to be exposed on the upper surface of the mesa section 95 along the extension direction of the trench section. As an example, the width of the base region 14 in the extension direction of the trench section may be set larger than the width of the contact region 15 in the extension direction of the trench section.

[0173] In the diode section 80, the length of the contact region 15 along the extension direction of the trench section is L A The base region 14 along the extension direction of the trench portion is L B When L A >L B For example, dI AK / dV AK This increases the surge current resistance and ensures a high surge current capability.

[0174] Alternatively, in the diode section 80, the length of the contact region 15 along the extension direction of the trench section is L A The base region 14 along the extension direction of the trench portion is L B When L A <L B For example, dI AK / dV AK Since the length L is increased, the effect of reducing the reverse recovery current is maintained at the reverse recovery of the rated current density, and the surge current resistance can be secured against surge currents of 5 times or more the rated current density. For example, A Length L B The ratio divided by L A / L B may be 10% or more and 90% or less.

[0175] At the position where the outer circumferential end position of the cathode region 82 in the X-axis direction is projected onto the top surface 21, there may be a region sandwiched between adjacent contact regions 15 in the X-axis direction and where no contact region 15 is formed. The base region 14 may be exposed on the surface of the mesa portion 95 on the outer circumferential side (-X-axis direction) of the position where the outer circumferential end position of the cathode region 82 in the X-axis direction is projected onto the top surface 21.

[0176] Fig. 20 is a diagram showing an example of the d-d' cross section in Fig. 19. In this cross section, the semiconductor device 200 of this example differs from the semiconductor device 100 shown in Fig. 2a in that it has a contact region 15 on the base region 14. By arranging the upper surface of the diode section 80 in an alternating manner such that the base region 14 and the contact region 15 are adjacent to each other, it is possible to reduce the forward voltage Vf during a large current.

[0177] 21a is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. The semiconductor device 300 of this example differs from the semiconductor device 100 shown in FIG. 1 in that a contact hole 54 is provided above the semiconductor substrate 10, spanning from the negative side in the Y-axis direction to the positive side in the Y-axis direction of the dummy trench portion 30.

[0178] From the region adjacent to the boundary 90 of the transistor portion 70 to the diode portion 80, the gate trench portion 40 is not provided, and instead, the dummy trench portion 30 is provided. For this reason, the width in the Y-axis direction of the contact hole 54 from the region adjacent to the boundary 90 of the transistor portion 70 to the diode portion 80 is wider than the contact hole 54 provided in the region of the transistor portion 70 excluding the boundary 90.

[0179] 1, the position of the end in the +X-axis direction (inner circumference side of the semiconductor device) of the contact region 15 formed at the end in the X-axis direction of the diode section 80 may be located in the -X-axis direction (outer circumference side) from the position where the cathode region 82 is projected onto the front surface of the semiconductor substrate 10. The area on the front surface of the base region 14 of the diode section 80 may be larger than the area where the cathode region 82 is projected onto the front surface of the semiconductor substrate 10.

[0180] The contact hole 54 of the diode section 80 may be formed across the multiple mesas 95 and the dummy trenches 30 in the arrangement direction of the dummy trenches 30. By forming the contact hole 54 across the multiple mesas 95 and the dummy trenches 30 in the diode section 80, the contact area between the diode section 80 and the emitter electrode 52 is increased. This makes it difficult for carriers to accumulate directly below the interlayer insulating film 38, thereby reducing the injection efficiency of minority carriers.

[0181] The contact hole 54 of the diode section 80 may extend to the boundary section 90. Furthermore, the contact hole 54 of the diode section 80 may extend, including the boundary section 90, to a mesa section 95 that contacts, on the diode section 80 side, the gate trench section 40 of the transistor section 70 that is located closest to the diode section 80 in the Y-axis direction. This makes it easier to extract accumulated carriers from the boundary region between the transistor section 70 and the diode section 80, including the boundary section 90.

[0182] Fig. 21b is a diagram showing an example of the s-s' cross section in Fig. 21a. The s-s' cross section is a YZ plane that passes through the emitter region 12, from the dummy trench portion 30 adjacent to the gate trench portion 40 on the negative side in the Y axis direction to the dummy trench portion 30 adjacent to the gate trench portion 40 on the positive side in the Y axis direction, in the transistor portion 70 of the semiconductor device 300 of this example.

[0183] In the s-s' cross section, the semiconductor device 300 has a collector electrode 24 provided on the lower surface 23 and an emitter electrode 52 provided on the upper surface 21. An N+ type emitter region 12, a P- type base region 14, and one or more N+ type accumulation regions 16 are arranged on the upper surface 21 side in this order from the upper surface 21 side. An N- type drift region 18 is formed below the accumulation region 16. An N+ type buffer region 20 is formed below the drift region 18. A P+ type collector region 22 exposed at the lower surface 23 is formed below the buffer region 20.

[0184] An interlayer insulating film 38 is provided on the upper surface 21 above the gate trench portion 40. In the Y-axis direction, the interlayer insulating film 38 is not provided on the upper surface 21 between the dummy trench portion 30 and the interlayer insulating film 38 on the gate trench portion 40. In addition, the interlayer insulating film 38 is not provided on the upper surface 21 above the dummy trench portion 30.

[0185] In the s-s' cross section, the width Wi is the width in the Y-axis direction from the end P3 in the Y-axis direction of the gate trench portion 40 to the end P4 of the contact hole 54. The end P3 is the position where the trench sidewall of the gate trench portion 40 contacts the upper surface 21 in the XZ plane. The end P4 is the position of the end face of the interlayer insulating film 38 in the XZ plane in a cross section parallel to the YZ plane. More specifically, the end P4 may be the position where the end face of the interlayer insulating film 38 in the XZ plane contacts the upper surface 21. If the upper surface or side surface of the interlayer insulating film 38 is curved rather than flat, the end P4 may be the position where the interlayer insulating film 38 contacts the upper surface 21.

[0186] The width Wm is the width from the end P3 of the gate trench portion 40 to the end P3' of the dummy trench portion 30 adjacent to the gate trench portion 40 on the gate trench portion 40 side, i.e., the mesa width. The width Wm may be 1.5 to 3.5 times the width Wi. The width Wm may be 0.5 μm, for example. The width Wi may be 0.2 μm, for example.

[0187] The width from the end P4 to the end P3' of the dummy trench portion 30 adjacent to the gate trench portion 40 may be longer than the width Wi. By making the width from the end P4 to the end P3' longer than the width Wi, carriers can be easily extracted from the transistor portion 70, particularly when the transistor portion 70 is turned off. Latch-up of the transistor portion 70 is also suppressed.

[0188] Alternatively, the width from the end P4 to the end P3' of the dummy trench portion 30 adjacent to the gate trench portion 40 may be shorter than the width Wi. When the width from the end P4 to the end P3' is shorter than the width Wi, it becomes easier to increase the carrier concentration around the gate trench portion 40. This leads to a reduction in the on-voltage of the transistor portion 70.

[0189] In the semiconductor device 300 of this embodiment, the interlayer insulating film 38 is not provided above the dummy trench portion 30 and above the semiconductor substrate 10 on the positive and negative sides of the dummy trench portion 30 in the Y-axis direction. That is, the emitter electrode 52 is continuously in contact with the multiple dummy trench portions 30 and the upper surface of the mesa portion 95 along the Y-axis direction. Therefore, in the mesa portion 95, a large margin can be taken in setting the position of the end P4 of the contact hole 54 in the Y-axis direction. That is, even if the width Wi is increased relative to the width Wm to increase the proportion of the width Wi in the width Wm, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be secured. In addition, by increasing the width Wi relative to the width Wm, the gate metal layer 50 and the gate conductive portion 44 can be more reliably insulated from each other.

[0190] Furthermore, in the semiconductor device 300 of this embodiment, since the interlayer insulating film 38 is not provided between the end P4 and the end P3' above the emitter region 12, even if the width Wm is made smaller than the width Wi and the proportion of the width Wi in the width Wm is increased, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be ensured. That is, the mesa width Wm can be made smaller. This improves the characteristics of the transistor section 70. Furthermore, since fine processing of the contact hole 54 is not required, the manufacturing cost of the semiconductor device 300 can be reduced.

[0191] Fig. 21c is a diagram showing an example of the t-t' cross section in Fig. 21a. The t-t' cross section is a YZ plane that extends from the transistor portion 70 to the diode portion 80 of the semiconductor device 300 of this example, and passes through the emitter region 12, the contact region 15, and the base region 14.

[0192] In the t-t' cross section, the transistor section 70 has a collector electrode 24 provided on the lower surface 23 and an emitter electrode 52 provided on the upper surface 21. On the upper surface 21 side, an N+ type emitter region 12, a P- type base region 14, and one or more N+ type accumulation regions 16 are formed in this order from the upper surface 21 side. Below the accumulation region 16, an N- type drift region 18 is formed.

[0193] An N+ type buffer region 20 is formed below the drift region 18. A P+ type collector region 22 exposed at the lower surface 23 is formed below the buffer region 20. An interlayer insulating film 38 is provided on the upper surface 21 above the gate trench portion 40.

[0194] In the Y-axis direction of the t-t' cross section of the transistor portion 70, the interlayer insulating film 38 is not provided on the upper surface 21 between the dummy trench portion 30 and the interlayer insulating film 38 on the gate trench portion 40. Moreover, the interlayer insulating film 38 is not provided on the upper surface 21 above the dummy trench portion 30. That is, the emitter electrode 52 is in continuous contact with the multiple dummy trench portions 30 and the upper surfaces of the mesa portion 95 along the Y-axis direction.

[0195] In the t-t' cross section, boundary portion 90 has collector electrode 24 provided on lower surface 23 and emitter electrode 52 provided on upper surface 21. In addition, on the upper surface 21 side, P+ type contact region 15 and P- type base region 14 are formed in this order from the upper surface 21 side. Below base region 14, N- type drift region 18 is formed.

[0196] An N+ type buffer region 20 is formed below the drift region 18. A P+ type collector region 22 exposed at a lower surface 23 is formed below the buffer region 20. The collector region 22 may be a region in which the collector region 22 of the transistor portion 70 extends in the Y-axis direction. In the Y-axis direction in the t-t' cross section of the boundary portion 90, the interlayer insulating film 38 is not provided on the upper surface 21 above the dummy trench portion 30 and above the contact region 15.

[0197] The emitter electrode 52 is in continuous contact with the dummy trench portion 30 and the upper surface of the mesa portion 95 along the Y-axis direction from the gate trench portion 40 provided closest to the boundary portion 90 to the boundary portion 90 without including the interlayer insulating film .

[0198] In the t-t' cross section, the diode section 80 has a collector electrode 24 provided on the lower surface 23 and an emitter electrode 52 provided on the upper surface 21. A P-type base region 14 and one or more N+ type accumulation regions 16 are formed on the upper surface 21 side in this order from the upper surface 21 side. An N-type drift region 18 is formed below the accumulation region 16. An N+ type buffer region 20 is formed below the drift region 18. An N+ type cathode region 82 exposed to the lower surface 23 is formed below the buffer region 20.

[0199] In the t-t' cross section, the diode section 80 does not have the interlayer insulating film 38 provided on the upper surface 21 above the dummy trench section 30 and above the base region 14. That is, the emitter electrode 52 is in continuous contact with the multiple dummy trench sections 30 and the upper surfaces of the mesa section 95 along the Y-axis direction. The emitter electrode 52 is in continuous contact with the upper surfaces of the dummy trench section 30 and the mesa section 95 without including the interlayer insulating film 38 between the boundary section 90 and the diode section 80.

[0200] In the semiconductor device 300 of this example, the contact holes 54 are provided continuously in the Y-axis direction from a region of the transistor section 70 adjacent to the boundary section 90 to the diode section 80. Here, "the contact holes 54 are provided continuously in the Y-axis direction" means that there is no region in the Y-axis direction where the contact holes 54 are not provided, from a region of the transistor section 70 adjacent to the boundary section 90 to the diode section 80.

[0201] In the semiconductor device 300 of this example, the interlayer insulating film 38 is not provided between the end P4 and the end P3' above the emitter region 12, so even if the width Wi is made larger than the width Wm to increase the proportion of the width Wi in the width Wm, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be ensured. That is, a large margin can be secured between the end P3 and the end P4. Furthermore, by making the width Wi larger than the width Wm, the gate metal layer 50 and the gate conductive portion 44 can be more reliably insulated from each other.

[0202] Furthermore, in the semiconductor device 300 of this embodiment, since the interlayer insulating film 38 is not provided between the end P4 and the end P3' above the emitter region 12, even if the width Wm is made smaller than the width Wi and the proportion of the width Wi in the width Wm is increased, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be ensured. That is, the mesa width Wm can be made smaller. This improves the characteristics of the transistor section 70. Furthermore, since fine processing of the contact hole 54 is not required, the manufacturing cost of the semiconductor device 300 can be reduced.

[0203] FIG. 22 is a cross-sectional view of a semiconductor device 350 of the comparative example. In the semiconductor device 350 of the comparative example, an interlayer insulating film 38 is provided above the gate trench portion 40 and above the dummy trench portion 30. Therefore, in addition to the end P4, an end P4' of the interlayer insulating film 38 above the dummy trench portion 30 is arranged at a width Wi from the end P3' of the dummy trench portion 30 toward the gate trench portion 40. Therefore, in the semiconductor device 350 of the comparative example, when the width Wi is increased relative to the width Wm to increase the proportion of the width Wi in the width Wm, the end P4 and the end P4' are close to each other. Therefore, in the semiconductor device 350 of the comparative example, it is difficult to secure a contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54, compared with the semiconductor device 300 of FIG. 21b. That is, it is difficult to secure a large margin between the end P3 and the end P4. It is also difficult to secure a large margin between the end P3' and the end P4'.

[0204] In addition to the end P4, the semiconductor device 350 of the comparative example has an end P4' of the interlayer insulating film 38 above the dummy trench portion 30 disposed on the side of the gate trench portion 40 from the end P3' of the dummy trench portion 30. Therefore, when the width Wm is made smaller than the width Wi and the ratio of the width Wi to the width Wm is increased, the end P4 and the end P4' are close to each other. Therefore, in the semiconductor device 350 of the comparative example, it is difficult to ensure the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54, compared to the semiconductor device 300 of FIG. 21b. That is, it is difficult to reduce the mesa width Wm. Therefore, it is difficult to improve the characteristics of the transistor portion 70. Furthermore, since the contact hole 54 needs to be finely processed, it is difficult to reduce the manufacturing cost of the semiconductor device 300.

[0205] 23a is a diagram partially illustrating the upper surface of a semiconductor device 300 according to another embodiment of the present invention. The semiconductor device 300 of this example differs from the semiconductor device 300 of FIG. 21a in that the dummy trench portion 30 has a U-shape in top view, and a plurality of dummy trench portions 30 are sandwiched between the gate trench portions 40 in the Y-axis direction above the emitter region 12 and the contact region 15. In the semiconductor device 300 of this example, a plurality of dummy trench portions 30 are sandwiched between the gate trench portions 40 in the Y-axis direction above the emitter region 12 and the contact region 15, so that the width of the contact hole 54 in the Y-axis direction is set larger in the transistor portion 70 than in the semiconductor device 300 shown in FIG. 21a.

[0206] At the position where the outer circumferential end position in the X-axis direction of the cathode region 82 is projected onto the top surface 21, there may be a region sandwiched between adjacent contact regions 15 in the X-axis direction and where no contact region 15 is formed. The base region 14 may be exposed on the surface of the mesa portion 95 on the outer circumferential side (-X-axis direction) of the position where the outer circumferential end position in the X-axis direction of the cathode region 82 is projected onto the top surface 21.

[0207] Fig. 23b is a diagram showing an example of the u-u' cross section in Fig. 23a. The u-u' cross section is a YZ plane that passes through the emitter region 12 from the dummy trench portion 30 located on the positive side of the Y axis direction of the two dummy trench portions 30 arranged on the positive side of the Y axis direction of the gate trench portion 40 to the dummy trench portion 30 located on the negative side of the Y axis direction of the two dummy trench portions 30 arranged on the negative side of the Y axis direction of the gate trench portion 40 in the transistor portion 70 of the semiconductor device 300 of this example.

[0208] In the semiconductor device 300 of this example, the interlayer insulating film 38 is not provided between the end P4 and the end P3' above the emitter region 12, so that, similarly to the semiconductor device 300 shown in FIG. 21b, even if the width Wi is made larger than the width Wm to increase the proportion of the width Wi in the width Wm, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be ensured. That is, a large margin can be secured between the end P3 and the end P4. Furthermore, by making the width Wi larger than the width Wm, the gate metal layer 50 and the gate conductive portion 44 can be more reliably insulated from each other.

[0209] Furthermore, in the semiconductor device 300 of this embodiment, since the interlayer insulating film 38 is not provided between the end P4 and the end P3' above the emitter region 12, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be ensured even if the width Wm is made smaller than the width Wi and the proportion of the width Wi in the width Wm is increased, as in the semiconductor device 300 shown in FIG. 21b. That is, the mesa width Wm can be made smaller. This improves the characteristics of the transistor section 70. Furthermore, since fine processing of the contact hole 54 is not required, the manufacturing cost of the semiconductor device 300 can be reduced.

[0210] Fig. 23c is a diagram showing an example of the v-v' cross section in Fig. 21a. The v-v' cross section is a YZ plane that extends from the transistor portion 70 to the diode portion 80 of the semiconductor device 300 of this example, and passes through the emitter region 12, the contact region 15, and the base region 14.

[0211] 21c, the semiconductor device 300 of this example has a contact hole 54 provided from the transistor section 70 to the diode section 80. Since the semiconductor device 300 of this example does not have an interlayer insulating film 38 provided between the end P4 and the end P3' above the emitter region 12, the contact area between the emitter region 12 and the contact provided in the contact hole 54 can be secured even if the width Wi is made larger than the width Wm to increase the proportion of the width Wi in the width Wm, as in the semiconductor device 300 shown in FIG. 21c. In other words, a large margin can be secured between the end P3 and the end P4.

[0212] Furthermore, in the semiconductor device 300 of this embodiment, since the interlayer insulating film 38 is not provided between the end P4 and the end P3' above the emitter region 12, the contact area between the emitter region 12 and the emitter electrode 52 provided in the contact hole 54 can be ensured even if the width Wm is made smaller than the width Wi and the proportion of the width Wi in the width Wm is increased, as in the semiconductor device 300 shown in FIG. 21c. In other words, the mesa width Wm can be made smaller. This improves the characteristics of the transistor section 70. Furthermore, since fine processing of the contact hole 54 is not required, the manufacturing cost of the semiconductor device 300 can be reduced.

[0213] Fig. 24 is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. The semiconductor device 300 of this example differs from the semiconductor device 300 of Fig. 21a in that the gate runner 48 electrically connecting the gate trench portion 40 and the gate metal layer 50 is not provided, and the gate metal layer 50 is electrically connected to the gate trench portion 40 through a contact hole 49 provided on the gate trench portion 40 at the most negative side in the X-axis direction of the gate trench portion 40.

[0214] In the semiconductor device 300 of this example, the interlayer insulating film 38 is not provided above the dummy trench portion 30, and therefore, similarly to the semiconductor device 300 shown in Figures 21a to 21c, a contact area between the contact provided in the contact hole 54 and the emitter region 12 can be ensured, compared to a case in which the interlayer insulating film 38 is provided above the dummy trench portion 30. This makes it possible to improve the characteristics of the transistor portion 70. In addition, since fine processing of the contact hole 54 is not required, the manufacturing cost of the semiconductor device 300 can be reduced.

[0215] Fig. 25 is a diagram partially illustrating the top surface of a semiconductor device 300 according to another embodiment of the present invention. The semiconductor device 300 of this example differs from the semiconductor device 300 of Fig. 23a in that the gate runner 48 electrically connecting the gate trench portion 40 and the gate metal layer 50 is not provided, and the gate metal layer 50 is electrically connected to the gate trench portion 40 through a contact hole 49 provided on the gate trench portion 40 at the most negative side in the Y-axis direction of the gate trench portion 40.

[0216] In the semiconductor device 300 of this example, the interlayer insulating film 38 is not provided above the dummy trench portion 30, and therefore, similarly to the semiconductor device 300 shown in Figures 23a to 23c, a contact area between the contact provided in the contact hole 54 and the emitter region 12 can be ensured, compared to a case in which the interlayer insulating film 38 is provided above the dummy trench portion 30. This makes it possible to improve the characteristics of the transistor portion 70. In addition, since fine processing of the contact hole 54 is not required, the manufacturing cost of the semiconductor device 300 can be reduced.

[0217] Fig. 26 is a diagram showing an example of a semiconductor chip 120 according to an embodiment of the present invention. As shown in Fig. 26, in the semiconductor chip 120 of this example, the transistor sections 70 and the diode sections 80 are arranged alternately and periodically in the XY plane. Fig. 26 shows an example in which three transistor sections 70 are provided in the X-axis direction and seven diode sections 80 are provided in the Y-axis direction, and three diode sections 80 are provided in the X-axis direction and six diode sections 80 in the Y-axis direction.

[0218] The width WI is the width in the Y-axis direction of the transistor portion 70. The width WF is the width in the Y-axis direction of the diode portion 80. The width Wh is the width of a portion where the base region 14 is formed on the upper surface 21 side of the semiconductor substrate 10 and where the well region 11 is not formed, from the end of the well region 11 on the positive side in the X-axis direction to the end of the well region 11 on the negative side in the X-axis direction, as will be described later in FIG.

[0219] In the transistor section 70, the width Wh is the width from an end of the base region 14 that is in contact with the end of the well region 11 on the negative side in the X-axis direction and is exposed on the upper surface 21 of the semiconductor substrate 10 and is in contact with the well region 11, through the contact region 15 and the emitter region 12 that are exposed on the upper surface 21 of the semiconductor substrate 10, to an end of the base region 14 that is in contact with the end of the well region 11 on the positive side in the X-axis direction and is in contact with the well region 11, which is formed on the upper surface 21 of the semiconductor substrate 10. In the diode section 80, the width Wh is the width from an end of the base region 14 that is in contact with the end of the well region 11 on the negative side in the X-axis direction and is exposed on the upper surface 21 of the semiconductor substrate 10 and is in contact with the well region 11, through the contact region 15 and the base region 14 that are exposed on the upper surface 21 of the semiconductor substrate 10 and is in contact with the end of the well region 11 on the positive side in the X-axis direction and is in contact with the well region 11, which is formed on the upper surface 21 of the semiconductor substrate 10.

[0220] An edge termination portion may be present between the outer periphery of the semiconductor chip 120 and the transistor portion 70 and the diode portion 80. Furthermore, a gate metal layer 50, a gate pad portion (not shown) in which the gate metal layer 50 is aggregated, or another specified pad portion may be present between the edge termination portion and the transistor portion 70 and the diode portion 80. In the arrangement direction (Y-axis direction) of the transistor portion 70 and the diode portion 80, the transistor portion 70 may be disposed at the end on the outer periphery side and face the edge termination portion.

[0221] Fig. 27a is an enlarged view of region A in Fig. 26. Fig. 27a is a diagram showing the configuration of a cathode region 82 and a floating region 84 in a diode section 80. Fig. 27a omits configurations other than the cathode region 82 and the floating region 84, such as the gate trench section 40 and the dummy trench section 30 provided in the diode section 80 and the transistor section 70.

[0222] As shown in FIG. 27a, in the semiconductor device 300 of this example, ten floating regions 84 are provided in the X-axis direction and two in the Y-axis direction in the diode section 80 inside the cathode region 82 in the XY plane. An end S of a P+ type well region 11 is provided on the positive side of the diode section 80 and the transistor section 70 in the X-axis direction. An end S' of a P+ type well region 11 is provided on the negative side of the diode section 80 and the transistor section 70 in the X-axis direction. The well region 11 is formed outside the region where the transistor section 70 and the diode section 80 are alternately arranged. In other words, the well region 11 is not formed inside the transistor section 70 and the diode section 80 from the end S.

[0223] The positional relationship between the cathode region 82 and components other than the cathode region 82, such as the contact hole 54, the dummy trench portion 30, the contact region 15 formed at the X-axis end of the contact hole 54, and the high-concentration region 17, may be the positional relationship shown in the top views of Figures 1, 19, 21a, 23a, 24, and 25.

[0224] As shown in FIG. 27a, in the semiconductor device 300 of this example, the transistor section 70 is provided adjacent to the diode section 80 on both the Y-axis direction positive side, which is one side of the arrangement direction of the diode section 80 and the transistor section 70, and the Y-axis direction negative side, which is the other side of the arrangement direction. The width WI of the transistor section 70 in the Y-axis direction may be larger than the width WF of the diode section 80 in the Y-axis direction. The width WI may be two or more times and five or less times the width WF. The width WI may be 1500 μm, for example. The width WF may be 500 μm, for example. That is, the semiconductor device 300 of this example is an example in which the width WF is smaller than the semiconductor device 100 shown in FIG. 1 to FIG. 18 and the semiconductor device 200 shown in FIG. 19 to FIG. 20.

[0225] Furthermore, the width Wh from the end S of the well region 11 on the positive side in the X-axis direction to the end S' of the well region 11 on the negative side in the X-axis direction may be larger than the width WI. The width Wh may be 1.5 times or more and 3 times or less the width WI. The width Wh may be 3100 μm, for example.

[0226] The width Wh may be greater than the sum of the widths WI and WF. When the transistor section 70 is turned on or the diode section 80 is turned on, the snapback phenomenon in which the voltage between the collector electrode 24 and the emitter electrode 52 suddenly decreases in response to an increase in the current flowing between the collector electrode 24 and the emitter electrode 52 can be suppressed.

[0227] Fig. 27b is an enlarged view of region B1 in Fig. 27a. Fig. 27b shows an enlarged view from end S of well region 11 on the X-axis direction positive side of diode section 80 in Fig. 27a to end S' of well region 11 on the X-axis direction negative side. As shown in Fig. 27b, in the semiconductor device 300 of this example, ten floating regions 84 are provided in the X-axis direction and two in the Y-axis direction, for example, on the inside of cathode region 82 in the XY plane in diode section 80.

[0228] The width Wwc in the X-axis direction from the end S of the well region 11 on the X-axis direction positive side to the end of the cathode region 82 on the X-axis direction positive side in a top view may be smaller than the width WF of the diode portion 80. The width Wwc may be 0.25 to 0.75 times the width WF. The width Wwc may be 250 μm, for example.

[0229] 27b, end T of contact hole 54 on the positive side in the X-axis direction is provided at a distance of width Wwca on the negative side in the X-axis direction from end S on the positive side in the X-axis direction of well region 11. Also, end T' of contact hole 54 on the negative side in the X-axis direction is provided at a distance of width Wwca on the positive side in the X-axis direction from end S' on the negative side in the X-axis direction of well region 11. Contact hole 54 is provided in the X-axis direction from end T to end T'.

[0230] Although one contact hole 54 is shown in Figure 27b, in reality, as is clear from the top views of Figures 1, 19, 21a, 23a, 24 and 25, multiple contact holes 54 are provided in the Y-axis direction, with the ends T and T' of the contact hole 54 each being positioned at the same position in the Y-axis direction.

[0231] The width Wwca from the end S on the positive side in the X-axis direction of the well region 11 to the end T on the positive side in the X-axis direction of the multiple contact holes 54 formed in the diode section 80 may be smaller than the width Wwcb in the X-axis direction from the end T to the end on the positive side in the X-axis direction of the cathode region 82 in a top view. The width Wwca may be 0.1 times or more and 0.9 times or less than the width Wwcb. As an example, the width Wwca may be 100 μm, and the width Wwcb may be 150 μm. The sum of the widths Wwca and Wwcb is the width Wwc. In addition, the width from the end S' on the negative side in the X-axis direction of the well region 11 to the end T' on the negative side in the X-axis direction of the multiple contact holes 54 formed in the diode section 80 may also be equal to the width Wwca. The width in the X-axis direction from the end T' to the end on the negative side in the X-axis direction of the cathode region 82 in a top view may also be equal to the width Wwcb.

[0232] The width in the X-axis direction from the end S' of the well region 11 on the negative side in the X-axis direction to the end of the cathode region 82 on the negative side in the X-axis direction in top view may also be equal to the width Wwc. The contact hole 54 in Fig. 27b is one of a plurality of contact holes. The contact hole 54 may be the contact hole 54 shown in Figs. 21a to 25.

[0233] As shown in FIG. 27b, a floating region 84 is provided inside the cathode region 82 in the XY plane. The floating region 84 is a region of a second conductivity type that is in an electrically floating state. In this example, the floating region 84 is of a P+ type. The electrically floating state refers to a state in which the floating region is not connected to either the collector electrode 24 or the emitter electrode 52.

[0234] In the semiconductor device 300 of this example, the floating regions 84 are arranged in a lattice pattern in the XY plane. Here, the lattice pattern means that the floating regions 84 are arranged periodically in both the X-axis direction and the Y-axis direction. Fig. 27b shows an example in which two floating regions 84 are provided in the Y-axis direction, and ten floating regions 84 are provided in the X-axis direction, spanning from the negative side of the cathode region 82 in the X-axis direction to the positive side of the X-axis direction, with an opening region 85 in between.

[0235] The width Wff1 is the width of the opening region 85 in the X-axis direction. The width Wff1 is smaller than the width Wf1 of the floating region 84 in the X-axis direction. The width Wff1 may be smaller than the width WF of the diode portion 80. The width Wff1 may be 0.01 to 0.05 times the width WF. The width Wff1 may be 10 μm, for example.

[0236] The width Wf1 of the floating region 84 in the X-axis direction may be smaller than the width WF of the diode section 80. The width Wf1 may be 0.25 to 0.75 times the width WF. The width Wf1 may be 240 μm, for example.

[0237] The width Wf2 of the floating region 84 in the Y-axis direction may be smaller than the width WF of the diode portion 80. The width Wf2 may be 0.25 times or more and 0.75 times or less of the width WF. The width Wf2 may be equal to or different from the width Wf1. The width Wf2 may be 240 μm, for example.

[0238] The width Wcf1 from the end of the cathode region 82 on the positive side in the X-axis direction to the end of the floating region 84 on the most positive side in the X-axis direction may be smaller than the width Wff1. The width Wcf1 may be 0.1 to 0.9 times the width Wff1. The width Wcf1 may be any value other than zero. The width Wcf1 may be 5 μm, for example. The width from the end of the cathode region 82 on the negative side in the X-axis direction to the end of the floating region 84 on the most negative side in the X-axis direction may also be equal to the width Wcf1.

[0239] In the semiconductor device 300 of this example, two floating regions 84 are provided in the Y-axis direction, sandwiching an opening region 85 therebetween. Here, the width Wff2 is the width of the opening region 85 in the Y-axis direction. The width Wff2 may be smaller than the width Wf2. The width Wff2 may be 0.01 to 0.05 times the width WF of the diode section 80. The width Wff2 may be equal to or different from the width Wff1. The width Wff2 may be 10 μm, for example.

[0240] The ratio of the area of ​​the floating region 84 in the XY plane to the area of ​​the cathode region 82 in the XY plane may be 50% or more and 99% or less. That is, the area of ​​the floating region 84 in the XY plane may be smaller than the area of ​​the cathode region 82 in the XY plane. As an example, when Wh is 3100 μm, Wwc is 250 μm, Wf1 and Wf2 are 240 μm, Wcf1 and Wcf2 are 5 μm, and Wff1 and Wff2 are 10 μm, the total area of ​​the floating region 84 in the XY plane to the area of ​​the cathode region 82 is 88.6%.

[0241] A width Wcf2 from the end of the cathode region 82 on the positive side in the Y-axis direction to the end of the floating region 84 on the positive side in the Y-axis direction may be smaller than the width WF of the diode section 80. The width Wcf2 may be 0.01 to 0.05 times the width WF. The width Wcf2 need only be non-zero. The width Wcf2 may be equal to or different from the width Wcf1. The width from the end of the cathode region 82 on the negative side in the Y-axis direction to the end of the floating region 84 on the negative side in the Y-axis direction is also equal to the width Wcf2.

[0242] In this example, the width Wcnt of the contact holes 54 in the arrangement direction (Y-axis direction) may be smaller than Wff1. In this example, the width Wcnt may be smaller than Wff2. In this example, the width Wcnt may be smaller than Wcf1. In this example, the width Wcnt may be smaller than Wcf2. As an example, the width Wcnt is 0.5 μm.

[0243] FIG. 27c is an enlarged view of region B2 in FIG. 27b. As shown in FIG. 27c, in the semiconductor device 300 of this example, width Wcf1 is the width from the end of the cathode region 82 on the X-axis direction positive side to the end of the floating region 84 on the X-axis direction positive side that is disposed on the most positive side in the X-axis direction. Width Wcf2 is the width from the end of the cathode region 82 on the Y-axis direction positive side to the end of the floating region 84 on the Y-axis direction positive side. Width Wcf2 may be 5 μm, for example. Width Wff1 is the width of the opening region 85 in the X-axis direction. Width Wf1 is the width of the floating region 84 in the X-axis direction.

[0244] Figure 27d is a diagram showing an example of the h-h' cross section in Figure 27b. In the semiconductor device 300 of this example, in the diode section 80, a floating region 84 is provided in the buffer region 20 provided above the cathode region 82. Two floating regions 84 are provided in the Y-axis direction in the h-h' cross section.

[0245] In this example, as shown in FIG. 27d, there are two boundary positions between the collector region 22 and the cathode region 82 in a plane parallel to the lower surface 23 of the semiconductor substrate 10. Of the two boundary positions, boundary position P1 is the boundary position on the positive side in the Y-axis direction. Also, boundary position P1' is the boundary position on the negative side in the Y-axis direction of the two boundary positions. Boundary positions P1 and P1' are boundary positions in a cross section parallel to the h-h' cross section. As an example, the h-h' cross section is a plane perpendicular to the lower surface 23 and parallel to the arrangement direction of the dummy trench portions 30.

[0246] In this example, as shown in Fig. 27d, there are two end positions of the floating region 84 in a plane parallel to the lower surface 23. The boundary position P2 is the end position closest to the boundary position P1 of the floating region 84 arranged on the positive side in the Y axis direction among the two floating regions 84 arranged in the Y axis direction in the plane parallel to the lower surface 23. The boundary position P2' is the end position closest to the boundary position P1' of the floating region 84 arranged on the negative side in the Y axis direction among the two floating regions 84 arranged in the Y axis direction in the plane parallel to the lower surface 23.

[0247] In this example, an opening region 85 where no floating region 84 is provided is present at approximately the same depth position as the floating region 84 in the Z-axis direction. The opening region 85 may refer to a region sandwiched between the floating regions 84. As an example, the opening region 85 is an N+ type region. The doping concentration of the opening region 85 may be approximately the same as the doping concentration of the drift region 18 or the buffer region 20. The opening region 85 may be the drift region 18 or the buffer region 20 remaining without the floating region 84 being formed.

[0248] The width Wcf2 is the distance from the end position P1 to the end position P2. The width Wcf2 is also the distance from the end position P1' to the end position P2'. The width Wcf2 may be the same as the distance L1 in the example of FIG.

[0249] The width Wff2 is the distance in the Y-axis direction between adjacent floating regions 84 across the opening region 85. The width Wff2 may be the same as the distance L3 in the example of FIG.

[0250] The width Wd is the width of the floating region 84 in the Z-axis direction. The width Wd may be the same as the distance L4 in the example of FIG. 9. The width Wd of the floating region 84 in the Z-axis direction may be smaller than the width Wcf2. The width Wd may be 0.05 times or more and 0.5 times or less the width Wcf2. As an example, the width Wd may be 0.5 μm.

[0251] Figure 27e is a diagram showing an example of the j-j' cross section in Figure 27b. The j-j' cross section is an XZ plane passing through the line J''-J''' in Figure 27d. In the semiconductor device 300 of this example, a floating region 84 is provided in the buffer region 20 provided above the cathode region 82 in the diode section 80.

[0252] In this example, as shown in FIG. 27e, there are two boundary positions between the collector region 22 and the cathode region 82 in a plane parallel to the lower surface 23 of the semiconductor substrate 10. Of the two boundary positions, boundary position P5 is the boundary position on the negative side in the X-axis direction. Also, boundary position P5' is the boundary position on the positive side in the X-axis direction of the two boundary positions. Boundary positions P5 and P5' are boundary positions in a cross section parallel to the j-j' cross section. As an example, the j-j' cross section is a plane perpendicular to the lower surface 23 and parallel to the extension direction of the dummy trench portion 30.

[0253] 27e, in the present example, there are two end positions of the floating region 84 in a plane parallel to the lower surface 23. Boundary position P6 is the end position closest to boundary position P5 of the floating region 84 arranged on the most negative side in the X-axis direction among the multiple floating regions 84 arranged in the X-axis direction in the plane parallel to the lower surface 23. Moreover, boundary position P6' is the end position closest to boundary position P5' of the floating region 84 arranged on the most positive side in the X-axis direction among the multiple floating regions 84 arranged in the Y-axis direction in the plane parallel to the lower surface 23.

[0254] In this example, an opening region 85 where no floating region 84 is provided is present at approximately the same depth position as the floating region 84 in the Z-axis direction. The opening region 85 may refer to a region sandwiched between the floating regions 84. As an example, the opening region 85 is an N+ type region. The doping concentration of the opening region 85 may be approximately the same as the doping concentration of the drift region 18 or the buffer region 20. The opening region 85 may be the drift region 18 or the buffer region 20 remaining without the floating region 84 being formed.

[0255] The width Wf1 is the width of the floating region 84 in the X-axis direction. The width Wcf1 is the distance in the X-axis direction from the end position P5 to the end position P6. The width Wcf1 is the distance in the X-axis direction from the end position P5' to the end position P6'. The width Wff1 is the interval between the adjacent floating regions 84 across the opening region 85 in the X-axis direction. The width Wcf1 may be smaller than the width Wff1. In the semiconductor device 300 of this example, the floating regions 84 are provided in a lattice pattern in the XY plane in the diode section 80, so that a surge voltage (overshoot voltage) during reverse recovery of the diode section 80 can be suppressed.

[0256] Fig. 28a is another enlarged view of region A in Fig. 26. In the semiconductor device 300 of this example, similar to the semiconductor device 300 shown in Fig. 27a, transistor sections 70 are provided adjacent to the diode section 80 on the positive and negative sides of the diode section 80 in the Y-axis direction.

[0257] The semiconductor device 300 of this example differs from the semiconductor device 300 shown in FIG. 27a in the arrangement of the floating region 84 in the diode section 80. As shown in FIG. 28a, in the semiconductor device 300 of this example, the floating region 84 is continuously provided inside the cathode region 82 in the XY plane in the diode section 80 from the boundary side of the cathode region 82 on the positive side in the Y-axis direction, indicated by the dashed line, to the boundary side on the negative side in the Y-axis direction, indicated by the dashed line. Here, the floating region 84 being continuously provided in the Y-axis direction means that there is no region in the X-axis direction where the floating region 84 is not provided, at any location in the Y-axis direction from the boundary side on the positive side in the Y-axis direction to the boundary side on the negative side in the Y-axis direction of the cathode region 82.

[0258] Fig. 28b is an enlarged view of region C1 in Fig. 28a. Fig. 28b shows an enlarged view from end S of well region 11 on the positive side in the X-axis direction of diode portion 80 in Fig. 28a to end S' of well region 11 on the negative side in the X-axis direction.

[0259] In this example, the floating region 84 is provided in a stripe shape in the XY plane. Here, the stripe shape means that a plurality of rectangular floating regions 84 are provided at a predetermined interval in the short side direction of the rectangle. FIG. 28b shows an example in which a plurality of rectangular floating regions 84, each with a long side in the Y-axis direction and a short side in the X-axis direction, are provided in the XY plane from the most negative side to the most positive side in the X-axis direction of the cathode region 82 with a width Wff1' in the X-axis direction. The width Wff1' may be smaller than the width WF of the diode section 80. The width Wff1' may be 0.01 times or more and 0.05 times or less of the width WF. The width Wff1' may be 10 μm, for example.

[0260] The width Wf1' of the floating region 84 in the X-axis direction may be smaller than the width WF of the diode section 80. The width Wf1' may be 0.04 to 0.13 times the width WF. The width Wf1' may be 40 μm, for example.

[0261] The width Wf2' of the floating region 84 in the Y-axis direction may be smaller than the width WF of the diode portion 80. The width Wf2' may be 0.5 to 0.99 times the width WF. The width Wf2' may be 490 μm, for example.

[0262] The width Wcf1 is the width from the end of the cathode region 82 on the positive side in the X-axis direction to the end of the floating region 84 on the most positive side in the X-axis direction. The width Wcf1 may be smaller than the width Wff1'. The width Wcf1 may be 0.1 to 0.9 times the width Wff1'. The width Wcf1 may be any value other than zero. As in the example of FIG. 27b, the width Wcf1 may be 5 μm, for example. Note that the width from the end of the cathode region 82 on the negative side in the X-axis direction to the end of the floating region 84 on the most negative side in the X-axis direction is also equal to the width Wcf1.

[0263] The ratio of the area of ​​the floating region 84 in the XY plane to the area of ​​the cathode region 82 in the XY plane may be 50% or more and 99% or less, similar to the example of FIG. 27b. That is, the area of ​​the floating region 84 in the XY plane may be smaller than the area of ​​the cathode region 82 in the XY plane. As an example, when Wh is 3100 μm, Wwc is 250 μm, Wf1′ is 40 μm, Wf2′ is 490 μm, Wcf1 and Wcf2 are 5 μm, and Wff1′ is 10 μm, 51 floating regions 84 are provided in the X-axis direction and one in the Y-axis direction inside the cathode region 82 in a top view. In this case, the total area of ​​the floating region 84 in the XY plane to the area of ​​the cathode region 82 in the XY plane is 76.8%.

[0264] The width Wcf2 from the end of the cathode region 82 on the positive side in the Y-axis direction to the end of the floating region 84 on the positive side in the Y-axis direction may be smaller than the width WF of the diode section 80, as in the example of FIG. 27b. The width Wcf2 may be 0.01 to 0.05 times the width WF. The width Wcf2 may be equal to or different from the width Wcf1. The width Wcf2 may be any value other than zero. The width from the end of the cathode region 82 on the negative side in the Y-axis direction to the end of the floating region 84 on the negative side in the Y-axis direction is also equal to the width Wcf2.

[0265] FIG. 28c is an enlarged view of the region C2 in FIG. 28b. As shown in FIG. 28c, in the semiconductor device 300 of this example, the width Wcf1 is the width from the end of the cathode region 82 on the positive side in the X-axis direction to the end of the floating region 84 on the positive side in the X-axis direction, which is located on the most positive side in the X-axis direction. In addition, in the semiconductor device 300 of this example, the width Wcf2 is the width from the end of the cathode region 82 on the positive side in the Y-axis direction to the end of the floating region 84 on the positive side in the Y-axis direction. The width Wcf2 may be 5 μm, for example. The width Wff1′ is the width of the opening region 85 in the X-axis direction. The width Wf1′ is the width of the floating region 84 in the X-axis direction.

[0266] Fig. 28d is a diagram showing an example of the k-k' cross section in Fig. 28b. In the semiconductor device 300 of this example, in the diode section 80, a floating region 84 is provided in the buffer region 20 provided above the cathode region 82. In the k-k' cross section, the floating region 84 is provided continuously from the positive side to the negative side in the Y-axis direction.

[0267] In this example, as shown in FIG. 28d, there are boundary positions P1 and P2, as well as boundary positions P1' and P2', similar to the example of FIG. 27d. In this example, the floating region 84 is continuously provided from the end position P2 to the end position P2', so there is no opening region 85. Similarly to the example of FIG. 27d, the width Wcf2 is the distance from the end position P1 to the end position P2. Similarly to the example of FIG. 27d, the width Wcf2 is the distance from the end position P1' to the end position P2'. Similarly to FIG. 27c, the width Wd of the floating region 84 in the Z-axis direction may be smaller than the width Wcf2. The width Wd may be 0.05 times or more and 0.5 times or less of the width Wcf2. As an example, the width Wd may be 0.5 μm.

[0268] Figure 28e is a diagram showing an example of the mm-m' cross section in Figure 28b. The mm-m' cross section is an XZ plane passing through line m''-m''' in Figure 28d. In the semiconductor device 300 of this example, a floating region 84 is provided in the buffer region 20 provided above the cathode region 82 in the diode section 80.

[0269] In this example, as shown in Fig. 28e, boundary positions P5 and P6, as well as boundary positions P5' and P6', exist similarly to the example of Fig. 27e. As an example, the m-m' cross section is a plane that is perpendicular to the lower surface 23 of the semiconductor substrate 10 and parallel to the extension direction of the dummy trench portion 30. In this example, as in the example of Fig. 27e, an opening region 85 in which no floating region 84 is provided exists at the same depth position as the floating region 84 in the Z-axis direction.

[0270] Width Wf1' is the width of floating region 84 in the X-axis direction. Width Wcf1 is the distance from end position P5 to end position P6, similar to the example of FIG. 27e. Width Wcf1 is the distance from end position P5' to end position P6'. Width Wff1' is the distance between adjacent floating regions 84 across opening region 85 in the X-axis direction. Width Wcf1 may be smaller than width Wff1'.

[0271] In the semiconductor device 300 of this example, a plurality of floating regions 84 are provided in the diode section 80, extending from the end position P6 to the end position P6', sandwiching an opening region 85 therebetween. In the semiconductor device 300 of this example, the floating regions 84 are provided in a stripe pattern in the XY plane, so that a surge during reverse recovery of the diode section 80 can be suppressed.

[0272] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications or improvements can be made to the above embodiments. It is clear from the claims that such modifications or improvements can also be included in the technical scope of the present invention. As an example, a high concentration region of the first conductivity type may be formed in the boundary portion 90. In this case, the integrated concentration of the high concentration region in the boundary portion 90 may be smaller than the integrated concentration of the accumulation region 16 in the transistor portion 70 and may be smaller than the integrated concentration of the high concentration region 17 in the diode portion 80.

[0273] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0274] 10 semiconductor substrate, 11 well region, 12 emitter region, 14 base region, 15 contact region, 16 accumulation region, 16-1 accumulation region, 16-2 accumulation region, 16-3 accumulation region, 17 high concentration region, 17-1 high concentration region, 17-2 high concentration region, 18 drift region, 20 buffer region, 21 upper surface, 22 collector region, 23 lower surface, 24 collector electrode, 25 connection portion, 30 dummy trench portion, 32 dummy insulating film, 34 dummy conductive portion, 38 interlayer insulating film, 40 gate trench portion, 42 gate insulating film, 44 gate conductive portion, 48 gate lath inner layer, 49 contact hole, 50 gate metal layer, 52 emitter electrode, 54 contact hole, 56 contact hole, 70 transistor portion, 80 diode portion, 82 cathode region, 84 floating region, 85 opening region, 86 dummy region, 87 high concentration hole region, 88 lifetime killer, 89 crystal defect layer, 90 boundary portion, 91, 92, 93, 94 waveform, 95 mesa portion, 95-1 mesa portion, 95-2 mesa portion, 95-3 mesa portion, 100 semiconductor device, 150 semiconductor device, 200 semiconductor device, 300 semiconductor device, 350 semiconductor device

Claims

[Claim 1] A semiconductor device including a plurality of trenches on an upper surface side of a semiconductor substrate, and a first mesa portion and a second mesa portion being regions between the trenches, A drift region of a first conductivity type; a second conductivity type base region provided in the first mesa portion and the second mesa portion above the drift region; a high concentration region of a first conductivity type provided between the drift region and the base region in a depth direction of the semiconductor substrate and having a doping concentration higher than that of the drift region; Equipped with The depth position of the lower end of the high concentration region between the base region and the drift region of the first mesa portion is deeper than the depth position of the lower end of the high concentration region between the base region and the drift region of the second mesa portion. Semiconductor device.

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