Semiconductor Device

Abstract

To suppress a backflow of a hole in a boundary between an IGBT range and a diode range.SOLUTION: In a semiconductor device, a semiconductor substrate comprises: a p-type collection region in contact with a lower electrode; an n-type cathode region in contact with the lower electrode in a position adjacent to the collector region; an insulated gate bipolar transistor range overlapping the collector region when viewed along a thickness direction of the semiconductor substrate; a diode range overlapping the cathode region when viewed along the thickness direction of the semiconductor substrate; an n-type buffer region in contact with an upper surface of the collector region and an upper surface of the cathode region; an n-type drift region in contact with an upper surface of the buffer region; and a p-type current limitation region arranged in an upper part of a boundary between the collector region and the cathode region and in contact with the upper surface of the buffer region.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a semiconductor device.

[0002] Patent Document 1 discloses a semiconductor device having an insulated gate bipolar transistor (hereinafter, sometimes referred to as an IGBT) and a diode. The semiconductor substrate of this semiconductor device has an IGBT area and a diode area. A lower electrode is provided on the lower surface of the semiconductor substrate. Within the IGBT area, a p-type collector region in contact with the lower electrode is provided. Within the diode area, an n-type cathode region in contact with the lower electrode is provided. The collector region and the cathode region are adjacent to each other. An n-type buffer layer and a drift layer are provided on the collector region and the cathode region. A p-type body region and an n-type source region are provided above the IGBT area. The body region faces the gate electrode via a gate insulating film. A p-type anode region is provided above the diode area. An IGBT is formed within the IGBT area, and a diode is formed within the diode area. When the IGBT operates, the upper electrode functions as an emitter electrode, and the lower electrode functions as a collector electrode. When the diode operates, the upper electrode functions as an anode electrode and the lower electrode functions as a cathode electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-132620 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the semiconductor device of Patent Document 1, when the potential of the upper electrode becomes higher than the potential of the lower electrode, the diode turns on. That is, within the diode range, a current flows from the anode region to the cathode region. At this time, holes flow from the body region within the IGBT range to the cathode region within the diode range. That is, holes flow across the boundary between the IGBT range and the diode range. After that, when the voltage applied to the semiconductor device is reversed, the holes present in the drift region flow back and are discharged to the upper electrode. This causes reverse recovery loss. At this time, the holes present in the drift region near the boundary between the IGBT range and the diode range also flow back and are discharged to the upper electrode. In this way, when holes flow back at the boundary between the IGBT range and the diode range, high reverse recovery loss occurs. Therefore, this specification proposes a technology to suppress the backflow of holes at the boundary between the IGBT range and the diode range. [Means for solving the problem]

[0005] The semiconductor device disclosed in this specification has a semiconductor substrate, a lower electrode in contact with the lower surface of the semiconductor substrate, a gate insulating film, and a gate electrode. The semiconductor substrate has a p-type collector region in contact with the lower electrode, and an n-type cathode region in contact with the lower electrode at a position adjacent to the collector region. The semiconductor substrate has an insulated gate bipolar transistor range that overlaps with the collector region when viewed along the thickness direction of the semiconductor substrate, and a diode range that overlaps with the cathode region when viewed along the thickness direction of the semiconductor substrate. The semiconductor substrate has a buffer region, a drift region, a body region, a source region, an anode region, and a current limiting region. The buffer region is an n-type region that is distributed across the insulated gate bipolar transistor range and the diode range, is in contact with the upper surface of the collector region and the upper surface of the cathode region, and has a lower n-type impurity concentration than the cathode region. The drift region is an n-type region that is distributed across the insulated gate bipolar transistor range and the diode range, is in contact with the upper surface of the buffer region, and has a lower n-type impurity concentration than the buffer region. The body region is a p-type region that is disposed within the insulated gate bipolar transistor range and is in contact with the drift region. The source region is an n-type region that is disposed within the insulated gate bipolar transistor range and is separated from the drift region by the body region. The anode region is a p-type region that is disposed within the diode range and is in contact with the drift region. The current limiting region is a p-type region that is disposed above the boundary between the collector region and the cathode region, is in contact with the upper surface of the buffer region, is in contact with the drift region, and is floating within the n-type region formed by the buffer region and the drift region. The gate electrode faces the body region via the gate insulating film.

[0006] In this semiconductor device, the p-type current limiting region is floating in the n-type region composed of the buffer region and the drift region. Therefore, when the diode is on, holes cannot flow from the drift region into the current limiting region. Since the current limiting region is disposed above the boundary between the collector region and the cathode region, holes are prevented from flowing from the drift region into the cathode region near the boundary between the collector region and the cathode region. That is, when the diode is on, holes are prevented from flowing to the boundary between the IGBT range and the diode range. Therefore, when the voltage applied to the semiconductor device is subsequently reversed, holes are prevented from flowing back at the boundary between the IGBT range and the diode range. Therefore, in this semiconductor device, reverse recovery loss is suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of a semiconductor device 10. [Diagram 2] FIG. 13 is a cross-sectional view of a semiconductor device of a comparative example. [Diagram 3] 1 is a graph showing the relationship between width L1, reverse recovery loss Err, and forward voltage VFP. [Figure 4] FIG. 4 is a cross-sectional view of a semiconductor device according to a first modified example. [Diagram 5] FIG. 11 is a cross-sectional view of a semiconductor device according to a second modified example. [Figure 6] FIG. 2 is a cross-sectional view of a semiconductor device according to a first reference example. [Figure 7] FIG. 11 is a cross-sectional view of a semiconductor device according to a second reference example. [Figure 8] FIG. 11 is a cross-sectional view of a semiconductor device according to a third reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the semiconductor device disclosed in this specification as an example, the drift region may be in contact with a side surface of the current limiting region.

[0009] In the semiconductor device disclosed in this specification as an example, a p-type region floating in the n-type region formed by the buffer region and the drift region may not be present outside the current limiting region.

[0010] In one example semiconductor device disclosed in this specification, the distance in a direction along the underside of the semiconductor substrate from the boundary between the collector region and the cathode region to a side of the current limiting region above the cathode region may be 20 μm or more.

[0011] According to this configuration, the reverse recovery loss can be effectively suppressed.

[0012] The semiconductor device 10 of the embodiment shown in FIG. 1 has a semiconductor substrate 12. A lower surface 12b of the semiconductor substrate 12 is covered with a lower electrode 18. A p-type collector region 32 and an n-type cathode region 52 are provided inside the semiconductor substrate 12 and within a range in contact with the lower electrode 18. In the following, a range of the semiconductor substrate 12 that overlaps with the collector region 32 when viewed along the thickness direction of the semiconductor substrate 12 is referred to as an insulated gate bipolar transistor range 30 (i.e., an IGBT range 30). Also, a range of the semiconductor substrate 12 that overlaps with the cathode region 52 when viewed along the thickness direction of the semiconductor substrate 12 is referred to as a diode range 50.

[0013] The upper surface 12a of the semiconductor substrate 12 is covered by an interlayer insulating film 14. The interlayer insulating film 14 covers the upper surface 12a in a range spanning the IGBT region 30 and the diode region 50. The upper surface of the interlayer insulating film 14 is covered by an upper electrode 16. The upper electrode 16 covers the upper surface of the interlayer insulating film 14 in a range spanning the IGBT region 30 and the diode region 50. A plurality of contact holes 14a are provided in the interlayer insulating film 14. A plurality of contact holes 14a are provided in each of the IGBT region 30 and the diode region 50. The upper electrode 16 has a buried metal layer 16a arranged in the contact hole 14a and a surface metal layer 16b arranged on the interlayer insulating film 14. Each buried metal layer 16a is mainly composed of tungsten. The surface metal layer 16b is mainly composed of aluminum. The upper electrode 16 is in contact with the upper surface 12a of the semiconductor substrate 12 in each contact hole 14a.

[0014] A plurality of trenches 20 are provided in the upper surface 12a of the semiconductor substrate 12. The trenches 20 extend approximately parallel to each other. A plurality of trenches 20 are provided in each of the IGBT area 30 and the diode area 50. The inner surface of each trench 20 is covered with a gate insulating film 22. A gate electrode 24 is provided in each trench 20. Each gate electrode 24 is insulated from the semiconductor substrate 12 by the gate insulating film 22. The upper surface of each gate electrode 24 is covered with an interlayer insulating film 14. Each gate electrode 24 is insulated from the upper electrode 16 by the interlayer insulating film 14.

[0015] The collector region 32 is a p-type region having a high p-type impurity concentration. As described above, the collector region 32 is in contact with the bottom electrode 18 within the IGBT area 30. The collector region 32 is in ohmic contact with the bottom electrode 18.

[0016] The cathode region 52 is an n-type region having a high n-type impurity concentration. As described above, the cathode region 52 contacts the bottom electrode 18 within the diode area 50. More specifically, the cathode region 52 contacts the bottom electrode 18 in an area adjacent to the collector region 32. The cathode region 52 is in ohmic contact with the bottom electrode 18. A boundary 60 between the collector region 32 and the cathode region 52 coincides with the boundary between the IGBT area 30 and the diode area 50.

[0017] The semiconductor substrate 12 includes a buffer region 34, a drift region 36, a current confinement region 38, an upper p-type region 40, and a number of emitter regions 42.

[0018] The buffer region 34 is an n-type region having a lower n-type impurity concentration than the cathode region 52. The buffer region 34 is distributed from the IGBT range 30 to the diode range 50. The buffer region 34 contacts the upper surface of the collector region 32 and the upper surface of the cathode region 52.

[0019] The drift region 36 is an n-type region having a lower n-type impurity concentration than the buffer region 34. The drift region 36 is distributed from the IGBT region 30 to the diode region 50. The drift region 36 contacts the upper surface of the buffer region 34 in the IGBT region 30 and the diode region 50.

[0020] The current limiting region 38 is disposed in the n-type region 35 constituted by the buffer region 34 and the drift region 36. The entire periphery of the current limiting region 38 is surrounded by the n-type region 35. Therefore, the current limiting region 38 is floating in the n-type region 35. There is no floating p-type region in the n-type region 35 other than the current limiting region 38. The current limiting region 38 is disposed above the boundary 60 between the collector region 32 and the cathode region 52. That is, the current limiting region 38 is distributed across the IGBT region 30 and the diode region 50. The current limiting region 38 is in contact with the upper surface of the buffer region 34. The drift region 36 is in contact with the upper surface of the current limiting region 38. That is, above the boundary 60, the current limiting region 38 is disposed on the buffer region 34, and the drift region 36 is disposed on the current limiting region 38. The drift region 36 is in contact with the side of the current limiting region 38. The current limiting region 38 is distributed more widely in the diode region 50 than in the IGBT region 30. That is, in a direction parallel to the lower surface 12b of the semiconductor substrate 12 and perpendicular to the boundary 60, the distance from the boundary 60 to the end (i.e., side) of the current limiting region 38 on the cathode region 52 (hereinafter referred to as width L1) is longer than the distance from the boundary 60 to the end (i.e., side) of the current limiting region 38 on the collector region 32 (hereinafter referred to as width L2). The width L1 is longer than 20 μm.

[0021] Each emitter region 42 is an n-type region, and is disposed in a range including a portion of the upper surface 12a of the semiconductor substrate 12. Each emitter region 42 is in ohmic contact with the upper electrode 16 in the corresponding contact hole 14a. Each emitter region 42 is in contact with the gate insulating film 22 on the side surface of the corresponding trench 20. In this embodiment, a plurality of emitter regions 42 are provided in each of the IGBT region 30 and the diode region 50. However, in other embodiments, the emitter region 42 may not be provided in the diode region 50.

[0022] The upper p-type region 40 is disposed in a range including a portion of the upper surface 12a of the semiconductor substrate 12. The upper p-type region 40 is distributed from the IGBT range 30 to the diode range 50. Hereinafter, the upper p-type region 40 within the IGBT range 30 will be referred to as a body region 44, and the upper p-type region 40 within the diode range 50 will be referred to as an anode region 54.

[0023] The body region 44 is distributed from the side of the emitter region 42 to the lower side of the emitter region 42 in the IGBT area 30, and separates each emitter region 42 from the drift region 36. The body region 44 has a plurality of contact regions 44a and low concentration regions 44b. The p-type impurity concentration of each contact region 44a is higher than the p-type impurity concentration of the low concentration region 44b. Each contact region 44a is disposed on the side of the emitter region 42 in a range including a part of the upper surface 12a of the semiconductor substrate 12. Each contact region 44a is in ohmic contact with the upper electrode 16 in the corresponding contact hole 14a. The low concentration region 44b is disposed below the contact region 44a and the emitter region 42. The low concentration region 44b is in contact with the gate insulating film 22 below the emitter region 42. The low concentration region 44b is in contact with the upper surface of the drift region 36.

[0024] The anode region 54 is distributed within the diode range 50 from the side of the emitter region 42 to the lower side of the emitter region 42, and separates each emitter region 42 from the drift region 36. The anode region 54 has a plurality of contact regions 54a and low concentration regions 54b. The p-type impurity concentration of each contact region 54a is higher than the p-type impurity concentration of the low concentration regions 54b. Each contact region 54a is disposed on the side of the emitter region 42 in a range including a part of the upper surface 12a of the semiconductor substrate 12. Each contact region 54a is in ohmic contact with the upper electrode 16 in the corresponding contact hole 14a. The low concentration region 54b is disposed below the contact region 54a and the emitter region 42. The low concentration region 54b is in contact with the gate insulating film 22 below the emitter region 42. The low concentration region 54b is in contact with the upper surface of the drift region 36.

[0025] The drift region 36 contacts the gate insulating film 22 below the low concentration regions 44b and 54b.

[0026] Within the IGBT range 30, an IGBT is formed by the emitter region 42, body region 44, drift region 36, buffer region 34, collector region 32, gate electrode 24, gate insulating film 22, etc. When the IGBT is operated, a potential higher than that of the upper electrode 16 is applied to the lower electrode 18. When a potential equal to or higher than the gate threshold is applied to the gate electrode 24, a channel is formed in the low concentration region 44b of the body region 44, and the emitter region 42 and the drift region 36 are connected by the channel. This turns on the IGBT, and a current flows from the lower electrode 18 to the upper electrode 16.

[0027] Within the diode area 50, a PIN-type diode is formed by the anode region 54, the drift region 36, the buffer region 34, and the cathode region 52. When a potential higher than that of the lower electrode 18 is applied to the upper electrode 16, the diode turns on and a current flows from the upper electrode 16 to the lower electrode 18.

[0028] The operation of the diode in the diode range 50 will be described in detail. When a potential higher than that of the lower electrode 18 is applied to the upper electrode 16, holes flow from the anode region 54 (i.e., the contact region 54a and the low concentration region 54b) to the drift region 36, as shown by the arrow 100 in FIG. 1. As shown by the arrow 100, the holes that flow from the anode region 54 to the drift region 36 flow to the cathode region 52 via the buffer region 34. Also, in this state, electrons flow from the cathode region 52 to the anode region 54 via the buffer region 34 and the drift region 36. That is, electrons flow in the opposite direction to the arrow 100. Since holes and electrons flow in this way, a current flows from the upper electrode 16 to the lower electrode 18 in the diode range 50. After that, when the potential of the upper electrode 16 becomes lower than the potential of the lower electrode 18, the diode performs a reverse recovery operation. That is, the holes present in the drift region 36 are discharged to the upper electrode 16 via the anode region 54. As a result, a current (so-called reverse recovery current) flows instantaneously through the diode. This reverse recovery current causes a reverse recovery loss Err in the diode.

[0029] FIG. 2 shows a semiconductor device of a comparative example. The semiconductor device of the comparative example is different from the semiconductor device of the embodiment shown in FIG. 1 in that it does not have a current limiting region 38. In the semiconductor device of the comparative example, as in the semiconductor device of the first embodiment, holes flow into the diode range 50 as shown by the arrow 100 when the diode is on. In the semiconductor device of the comparative example, holes flow into the boundary between the IGBT range 30 and the diode range 50 when the diode is on, as shown by the arrow 102 in FIG. 2. That is, when the diode is on, holes flow from the body region 44 near the boundary between the IGBT range 30 and the diode range 50 to the drift region 36. As shown by the arrow 102, the holes that flow from the body region 44 to the drift region 36 flow into the cathode region 52 near the boundary 60 via the buffer region 34. In this way, if the current limiting region 38 does not exist, holes flow from the body region 44 in the IGBT range 30 to the cathode region 52 in the diode range 50. Thereafter, when the potential of the upper electrode 16 becomes lower than the potential of the lower electrode 18, the diode performs a reverse recovery operation. In the reverse recovery operation of the semiconductor device of the comparative example, a reverse recovery current flows in the diode range 50, similar to the reverse recovery operation of the semiconductor device 10 of the embodiment. In addition, in the semiconductor device of the comparative example, holes present in the drift region 36 near the boundary between the IGBT range 30 and the diode range 50 (i.e., holes present on the path indicated by the arrow 102) flow to the upper electrode 16 via the body region 44. That is, in the semiconductor device of the comparative example, a reverse recovery current flows not only in the diode range 50 but also at the boundary between the IGBT range 30 and the diode range 50. For this reason, the semiconductor device of the comparative example is prone to reverse recovery loss Err.

[0030] In contrast, in the semiconductor device 10 of the embodiment shown in FIG. 1, a p-type current limiting region 38 is provided above the boundary 60 between the collector region 32 and the cathode region 52. Therefore, when the diode is on, the pn junction at the interface between the current limiting region 38 and the drift region 36 acts as a barrier to prevent holes from flowing from the drift region 36 into the current limiting region 38. That is, in the semiconductor device 10 of the embodiment, the flow of holes indicated by the arrow 102 (i.e., the flow of holes at the boundary between the IGBT range 30 and the diode range 50) is prevented by the current limiting region 38. Therefore, when the diode is on, there are very few holes in the drift region 36 near the boundary between the IGBT range 30 and the diode range 50. Therefore, in the reverse recovery operation, the reverse recovery current flowing at the boundary between the IGBT range 30 and the diode range 50 is very small. Therefore, in the semiconductor device 10 of the embodiment, reverse recovery loss Err is unlikely to occur.

[0031] FIG. 3 shows the results of measuring the forward voltage VFP and reverse recovery loss Err of the diode for each sample of semiconductor devices that have different widths L1 of the current limiting region 38 in the diode range 50 and different p-type impurity concentrations Np of the current limiting region 38. As shown in FIG. 3, regardless of the p-type impurity concentration Np, the wider the width L1 of the current limiting region 38, the smaller the reverse recovery loss Err. This is considered to be because the wider the width L1 of the current limiting region 38, the more holes shown by the arrows 102 in FIGS. 1 and 2 are suppressed. Also, as shown in FIG. 3, regardless of the p-type impurity concentration Np, the wider the width L1 of the current limiting region 38, the higher the forward voltage VFP of the diode. This is considered to be because the wider the width L1 of the current limiting region 38, the narrower the range in which the current flows in the diode range 50. 3, the amount of decrease in reverse recovery loss Err when the width L1 is increased from 10 μm to 20 μm is greater than the amount of decrease in reverse recovery loss Err when the width L1 is increased from 0 μm to 10 μm and the amount of decrease in reverse recovery loss Err when the width L1 is increased from 20 μm to 30 μm. In this way, by setting the width L1 to 20 μm or more, the reverse recovery loss Err can be more effectively suppressed.

[0032] As described above, according to the semiconductor device 10 of the embodiment having the current limiting region 38 above the boundary 60 between the collector region 32 and the cathode region 52, the reverse recovery loss Err of the diode can be suppressed.

[0033] In another embodiment, as shown in FIG. 4, an n-type region 41 may be provided to divide the upper p-type region 40 into upper and lower parts. The n-type region 41 divides the low-concentration region 44b into a first low-concentration region 44b-1 located above the n-type region 41 and a second low-concentration region 44b-2 located below the n-type region 41. The n-type region 41 divides the low-concentration region 54b into a first low-concentration region 54b-1 located above the n-type region 41 and a second low-concentration region 54b-2 located below the n-type region 41. Even in this configuration, by adjusting the n-type impurity concentration of the n-type region 41, a current can be passed between the first low-concentration region 44b-1 and the second low-concentration region 44b-2 and between the first low-concentration region 54b-1 and the second low-concentration region 54b-2. Therefore, the first low concentration region 44b-1 and the second low concentration region 44b-2 can function as the body region 44, and the first low concentration region 54b-1 and the second low concentration region 54b-2 can function as the anode region 54.

[0034] 5, in another embodiment, the buffer region 34 may be in contact with the side surface of the current limiting region 38. Even in this configuration, the current limiting region 38 can suppress the reverse recovery loss Err.

[0035] Hereinafter, as Reference Examples 1 to 3, a description will be given of a configuration in which the reverse recovery current at the boundary is suppressed by something other than the current limiting region 38. That is, the semiconductor devices of Reference Examples 1 to 3 do not have the current limiting region 38.

[0036] (Reference example 1) In the semiconductor device of Reference Example 1 shown in FIG. 6, a portion 16b-2 of the surface metal layer 16b in the IGBT range 30 adjacent to the diode range 50 is made of a metal having a higher resistivity than the other portion 16b-1. More specifically, the portion 16b-1 is made of aluminum, and the portion 16b-2 is made of a metal having a higher resistivity than aluminum. Therefore, when the diode is on, holes are prevented from flowing through the path indicated by the arrow 102 in FIG. 6 (i.e., the boundary between the IGBT range 30 and the diode range 50). Therefore, in the reverse recovery operation of the diode, a reverse recovery current is prevented from flowing through the boundary between the IGBT range 30 and the diode range 50. Therefore, the reverse recovery loss Err can be suppressed.

[0037] (Reference example 2) In the semiconductor device of Reference Example 2 shown in FIG. 7, the buffer region 34 has a high concentration region 34a and a low concentration region 34b. The n-type impurity concentration of the low concentration region 34b is lower than the n-type impurity concentration of the high concentration region 34a. The low concentration region 34b is disposed in a position within the diode range 50 and adjacent to the boundary 60 between the collector region 32 and the cathode region 52. The high concentration region 34a constitutes the entire buffer region 34 within the IGBT range 30 and a portion of the buffer region 34 within the diode range 50 other than the vicinity of the boundary 60. Since the n-type impurity concentration of the low concentration region 34b is lower than the n-type impurity concentration of the high concentration region 34a, the resistivity of the low concentration region 34b is lower than the resistivity of the high concentration region 34a. Therefore, when the diode is on, holes are suppressed from flowing through the path indicated by the arrow 102 in FIG. 7 (i.e., the boundary between the IGBT range 30 and the diode range 50). Therefore, in the reverse recovery operation of the diode, the reverse recovery current is prevented from flowing through the boundary between the IGBT range 30 and the diode range 50. Therefore, the reverse recovery loss Err can be suppressed.

[0038] (Reference example 3) In the semiconductor device of Reference Example 3 shown in FIG. 8, the interval between the trenches 20 is narrower in the range 30x adjacent to the boundary between the IGBT range 30 and the diode range 50 in the IGBT range 30 than in the other ranges. Therefore, the width of the body region 44 in the range 30x at the portion sandwiched between the trenches 20 is narrow. Therefore, when the diode is on, holes are less likely to flow from the body region 44 in the range 30x to the drift region 36. In addition, the narrow width of the contact hole 14a in the range 30x also suppresses holes from flowing from the body region 44 in the range 30x to the drift region 36. Therefore, when the diode is on, holes are suppressed from flowing in the path indicated by the arrow 102 in FIG. 8 (i.e., the boundary between the IGBT range 30 and the diode range 50). Therefore, in the reverse recovery operation of the diode, the reverse recovery current is suppressed from flowing in the boundary between the IGBT range 30 and the diode range 50. Therefore, the reverse recovery loss Err can be suppressed.

[0039] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0040] 10: Semiconductor device 12: Semiconductor substrate 14: Interlayer insulating film 16:Top electrode 18: Lower electrode 20: Trench 22: Gate insulating film 24: Gate electrode 30: IGBT range 32: Collector area 34: Buffer area 36: Drift region 38: Current limit area 42: Emitter area 44: Body area 50: Diode range 52: Cathode region 54: Anode region 60: Boundary

Claims

1. A semiconductor device comprising: A semiconductor substrate; a lower electrode in contact with a lower surface of the semiconductor substrate; A gate insulating film; A gate electrode, having The semiconductor substrate is a p-type collector region in contact with the lower electrode; an n-type cathode region in contact with the lower electrode at a position adjacent to the collector region; having The semiconductor substrate is an insulated gate bipolar transistor area overlapping with the collector region when viewed along a thickness direction of the semiconductor substrate; a diode area overlapping with the cathode region when viewed along a thickness direction of the semiconductor substrate; having The semiconductor substrate is an n-type buffer region that is distributed across the insulated gate bipolar transistor range and the diode range, that is in contact with an upper surface of the collector region and an upper surface of the cathode region, and that has a lower n-type impurity concentration than the cathode region; an n-type drift region that is distributed across the insulated gate bipolar transistor range and the diode range, is in contact with an upper surface of the buffer region, and has an n-type impurity concentration lower than that of the buffer region; a p-type body region disposed within the insulated gate bipolar transistor and in contact with the drift region; an n-type source region disposed within the insulated gate bipolar transistor and separated from the drift region by the body region; a p-type anode region disposed within the diode and in contact with the drift region; a p-type current limiting region disposed above the boundary between the collector region and the cathode region, in contact with an upper surface of the buffer region, in contact with the drift region, and floating within an n-type region formed by the buffer region and the drift region; having the gate electrode faces the body region via the gate insulating film; Semiconductor device.

2. The semiconductor device according to claim 1 , wherein the drift region is in contact with a side surface of the current limiting region.

3. 3. The semiconductor device according to claim 1, wherein a p-type region floating in said n-type region formed by said buffer region and said drift region does not exist other than in said current limiting region.

4. The semiconductor device according to any one of claims 1 to 3, wherein a distance in a direction along the lower surface of the semiconductor substrate from the boundary between the collector region and the cathode region to a side surface of the current limiting region above the cathode region is 20 μm or more.

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