Semiconductor device and semiconductor circuit

Abstract

To provide a semiconductor device in which destruction due to current concentration is suppressed.SOLUTION: A semiconductor device of an embodiment comprises: a semiconductor layer having a first surface and a second surface opposing the first surface, the semiconductor layer including a first trench provided on a first surface side and a second trench provided on the first surface side; a first gate electrode provided in the first trench; a second gate electrode provided in the second trench; a fourth gate electrode provided on a second surface side; a fifth gate electrode provided on the second surface side; a first electrode in contact with the first surface; a second electrode in contact with the second surface; a first electrode pad electrically connected to the first gate electrode; a second electrode pad electrically connected to the second gate electrode; a fourth electrode pad electrically connected to the fourth gate electrode; and a fifth electrode pad electrically connected to the fifth gate electrode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a semiconductor device and a semiconductor circuit. [Background technology]

[0002] An example of a power semiconductor device is an insulated gate bipolar transistor (IGBT) with a trench gate structure. In an IGBT with a trench gate structure, for example, a p-type collector region, an n-type drift region, and a p-type base region are provided on a collector electrode. A gate electrode is provided in a trench that penetrates the p-type base region and reaches the n-type drift region, with a gate insulating film sandwiched between them. Furthermore, an n-type emitter region connected to an emitter electrode is provided in a region adjacent to the trench on the surface of the p-type base region.

[0003] In the IGBT, a channel is formed in the p-type base region by applying a positive voltage higher than the threshold voltage to the gate electrode. Electrons are then injected from the n-type emitter region into the n-type drift region, and holes are injected from the p-type collector region into the n-type drift region. This causes an on-current, with electrons and holes as carriers, to flow between the collector electrode and the emitter electrode.

[0004] A termination region is provided around the cell region where the trench gate structure is provided. The termination region includes an electric field mitigation structure such as a guard ring. The provision of the termination region reduces the electric field strength at the edge of the cell region, thereby suppressing a decrease in breakdown voltage when the IGBT is in the off state.

[0005] At the edge of the cell region, carriers spread to the termination region where no cells exist when the IGBT is in the on state. When the IGBT is turned off, the carriers that spread to the termination region are concentrated at the edge of the cell region and then discharged. This causes current concentration at the edge of the cell region. This current concentration can lead to the destruction of the IGBT. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-53466 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a semiconductor device and a semiconductor circuit in which turn-off loss is reduced and breakdown due to current concentration is suppressed. [Means for solving the problem]

[0008] The semiconductor device of the embodiment includes a semiconductor layer having a first surface and a second surface opposite to the first surface, the semiconductor layer including a first trench provided on the side of the first surface and a second trench provided on the side of the first surface, a first gate electrode provided in the first trench, a second gate electrode provided in the second trench, a fourth gate electrode provided on the side of the second surface, a fifth gate electrode provided on the side of the second surface, a first electrode in contact with the first surface, a second electrode in contact with the second surface, a first electrode pad electrically connected to the first gate electrode, a second electrode pad electrically connected to the second gate electrode, a fourth electrode pad electrically connected to the fourth gate electrode, and a fifth electrode pad electrically connected to the fifth gate electrode. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a semiconductor circuit according to a first embodiment. [Figure 2] FIG. 1 is a schematic cross-sectional view of a portion of a semiconductor device according to a first embodiment. [Figure 3] FIG. 1 is a schematic plan view of a semiconductor device according to a first embodiment. [Figure 4] 3 is a timing chart of the semiconductor device according to the first embodiment. [Figure 5] FIG. 10 is a schematic plan view of a semiconductor device according to a second embodiment. [Figure 6] FIG. 10 is a schematic cross-sectional view of a part of a semiconductor device according to a third embodiment. [Figure 7] 10 is a timing chart of the semiconductor device according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same or similar components will be designated by the same reference numerals, and the description of components that have already been described will be omitted as appropriate.

[0011] In this specification, the distribution and absolute value of the impurity concentration in a semiconductor region can be measured using, for example, secondary ion mass spectrometry (SIMS). The relative magnitude relationship between the impurity concentrations in two semiconductor regions can be determined using, for example, scanning capacitance microscopy (SCM). The distribution and absolute value of the impurity concentration can be measured using, for example, spreading resistance analysis (SRA). SCM and SRA can determine the relative magnitude relationship and absolute value of the carrier concentration in a semiconductor region. By assuming the activation rate of the impurities, the relative magnitude relationship between the impurity concentrations in two semiconductor regions, the distribution of the impurity concentrations, and the absolute value of the impurity concentrations can be determined from the measurement results of SCM and SRA.

[0012] (First embodiment) The semiconductor device of the first embodiment includes a semiconductor layer having a first surface and a second surface opposite to the first surface, the semiconductor layer including a first trench provided on the first surface side, a second trench provided on the first surface side, and a third trench provided on the first surface side, a first gate electrode provided in the first trench, a second gate electrode provided in the second trench, a third gate electrode provided in the third trench, a fourth gate electrode provided on the second surface side, a fifth gate electrode provided on the second surface side, a first electrode in contact with the first surface, a second electrode in contact with the second surface, a first electrode pad electrically connected to the first gate electrode, a second electrode pad electrically connected to the second gate electrode, a third electrode pad electrically connected to the third gate electrode, a fourth electrode pad electrically connected to the fourth gate electrode, and a fifth electrode pad electrically connected to the fifth gate electrode.

[0013] Moreover, the semiconductor circuit of the first embodiment includes the above-mentioned semiconductor device and a control circuit that controls voltages applied to the first electrode pad, the second electrode pad, the third electrode pad, the fourth electrode pad, and the fifth electrode pad.

[0014] The semiconductor device of the first embodiment is an IGBT 100 with a double-sided gate structure having gate electrodes on the front and back sides of a semiconductor layer. The IGBT 100 also has three types of gate electrodes on the front side of the semiconductor layer that are independently controlled. The IGBT 100 also has two types of gate electrodes on the back side of the semiconductor layer that are independently controlled. The gate electrodes on the front side of the semiconductor layer have a trench gate structure provided in a trench. The following description will be given taking as an example a case where the first conductivity type is n-type and the second conductivity type is p-type.

[0015] 1 is a schematic diagram of a semiconductor circuit according to a first embodiment, which is a semiconductor module 1000.

[0016] The semiconductor module 1000 includes an IGBT 100 and a control circuit 150 .

[0017] 1 shows the layout of an IGBT 100. The IGBT 100 has a cell region 100a, a termination region 100b, a first front gate electrode pad 101 (first electrode pad), a second front gate electrode pad 102 (second electrode pad), a third front gate electrode pad 103 (third electrode pad), a first back gate electrode pad 104 (fourth electrode pad), and a second back gate electrode pad 105 (fifth electrode pad).

[0018] The termination region 100b surrounds the cell region 100a. A first front gate electrode pad 101, a second front gate electrode pad 102, and a third front gate electrode pad 103 are located on the front side of the IGBT 100. A first back gate electrode pad 104 and a second back gate electrode pad 105 are located on the back side of the IGBT 100.

[0019] 2 is a schematic cross-sectional view of a part of the semiconductor device of the first embodiment, taken along the line AA' in FIG.

[0020] The IGBT 100 of the first embodiment includes a semiconductor layer 10, an emitter electrode 12 (first electrode), a collector electrode 14 (second electrode), a first front surface gate insulating film 21, a second front surface gate insulating film 22, a third front surface gate insulating film 23, a first rear surface gate insulating film 24, a second rear surface gate insulating film 25, a main gate electrode 31 (first gate electrode), a control gate electrode 32 (second gate electrode), a pre-gate electrode 33 (third gate electrode), a rear surface cell gate electrode 34 (fourth gate electrode), a rear surface termination gate electrode 35 (fifth gate electrode), a front surface interlayer insulating layer 40, and a rear surface interlayer insulating layer 42.

[0021] The semiconductor layer 10 includes a main gate trench 51 (first trench), a control gate trench 52 (second trench), a pre-gate trench 53 (third trench), an n-type cell drain region 60 (sixth semiconductor region), an n-type termination drain region 62 (seventh semiconductor region), a p-type cell collector region 64 (fourth semiconductor region), a p-type termination collector region 65 (fifth semiconductor region), an n-type buffer region 66, an n-type drift region 68 (first semiconductor region), a p-type base region 70 (second semiconductor region), an n-type emitter region 72 (third semiconductor region), a p-type contact region 74, a p-type boundary region 76 (eighth semiconductor region), and a p-type guard ring region 78.

[0022] The semiconductor layer 10 has a first surface P1 and a second surface P2 facing the first surface P1. The first surface P1 is the front surface of the semiconductor layer 10, and the second surface P2 is the back surface of the semiconductor layer 10.

[0023] In this specification, a direction parallel to the first plane P1 is referred to as a first direction, and a direction parallel to the first plane P1 and perpendicular to the first direction is referred to as a second direction.

[0024] The semiconductor layer 10 includes a cell portion 10a and a termination portion 10b. The cell portion 10a is included in a cell region 100a of the semiconductor layer 10. The termination portion 10b is included in a termination region 100b of the semiconductor layer 10. The termination portion 10b surrounds the cell portion 10a.

[0025] The semiconductor layer 10 is made of, for example, single crystal silicon and has a thickness of, for example, 40 μm or more and 700 μm or less.

[0026] The emitter electrode 12 is provided on the first face P1 side of the semiconductor layer 10. At least a portion of the emitter electrode 12 contacts the first face P1 of the semiconductor layer 10. The emitter electrode 12 is made of, for example, a metal. An emitter voltage (Ve) is applied to the emitter electrode 12. The emitter voltage is, for example, 0 V.

[0027] The collector electrode 14 is provided on the second face P2 side of the semiconductor layer 10. At least a portion of the collector electrode 14 contacts the second face P2 of the semiconductor layer 10. The collector electrode 14 is made of, for example, a metal.

[0028] A collector voltage (Vc) is applied to the collector electrode 14. The collector voltage is, for example, 200V or more and 6500V or less.

[0029] The main gate trench 51 is provided in the cell region 100a. The main gate trench 51 is provided on the first surface P1 side of the cell portion 10a. The main gate trench 51 is a groove provided in the cell portion 10a. The main gate trench 51 extends in a first direction. The main gate trenches 51 are repeatedly provided in a second direction.

[0030] The control gate trench 52 is provided in the cell region 100a. The control gate trench 52 is provided on the first surface P1 side of the cell portion 10a. The control gate trench 52 is a groove provided in the cell portion 10a. The control gate trench 52 extends in a first direction. The control gate trenches 52 are repeatedly provided in a second direction.

[0031] The pre-gate trench 53 is provided in the cell region 100a. The pre-gate trench 53 is provided on the first surface P1 side of the cell portion 10a. The pre-gate trench 53 is a groove provided in the cell portion 10a. The pre-gate trench 53 extends in a first direction. The pre-gate trenches 53 are repeatedly provided in a second direction.

[0032] The main gate electrode 31 is provided in the cell region 100a. The main gate electrode 31 is provided on the first face P1 side of the cell portion 10a. At least a portion of the main gate electrode 31 is provided in the main gate trench 51. The first surface gate electrode pad 101 is electrically connected to the main gate electrode 31 using wiring (not shown).

[0033] The main gate electrode 31 is, for example, polycrystalline silicon containing n-type impurities or p-type impurities. A first gate voltage (Vg1) is applied to the main gate electrode 31. The first gate voltage (Vg1) is a voltage based on the emitter voltage (Ve).

[0034] Hereinafter, a transistor controlled by the first gate voltage (Vg1) applied to the main gate electrode 31 will be referred to as a main gate transistor.

[0035] The first surface gate insulating film 21 is provided between the main gate electrode 31 and the cell portion 10a. At least a portion of the first surface gate insulating film 21 is provided in the main gate trench 51. The first surface gate insulating film 21 is, for example, a silicon oxide film.

[0036] The control gate electrode 32 is provided in the cell region 100a. The control gate electrode 32 is provided on the first surface P1 side of the cell portion 10a. At least a portion of the control gate electrode 32 is provided in the control gate trench 52. The second surface gate electrode pad 102 is electrically connected to the control gate electrode 32 using wiring (not shown).

[0037] The control gate electrode 32 is, for example, polycrystalline silicon containing n-type impurities or p-type impurities. A second gate voltage (Vg2) is applied to the control gate electrode 32. The second gate voltage (Vg2) is a voltage based on the emitter voltage (Ve).

[0038] Hereinafter, a transistor controlled by the second gate voltage (Vg2) applied to the control gate electrode 32 will be referred to as a control gate transistor.

[0039] The second surface gate insulating film 22 is provided between the control gate electrode 32 and the cell portion 10a. At least a portion of the second surface gate insulating film 22 is provided in the control gate trench 52. The second surface gate insulating film 22 is, for example, a silicon oxide film.

[0040] The pre-gate electrode 33 is provided in the cell region 100a. The pre-gate electrode 33 is provided on the first face P1 side of the cell portion 10a. At least a portion of the pre-gate electrode 33 is provided in the pre-gate trench 53. The third surface gate electrode pad 103 is electrically connected to the pre-gate electrode 33 using wiring (not shown).

[0041] The pre-gate electrode 33 is, for example, polycrystalline silicon containing n-type impurities or p-type impurities. A third gate voltage (Vg3) is applied to the pre-gate electrode 33. The third gate voltage (Vg3) is a voltage based on the emitter voltage (Ve).

[0042] Hereinafter, a transistor controlled by the third gate voltage (Vg3) applied to the pre-gate electrode 33 will be referred to as a pre-gate transistor.

[0043] The third surface gate insulating film 23 is provided between the pre-gate electrode 33 and the cell portion 10a. At least a part of the third surface gate insulating film 23 is provided in the pre-gate trench 53. The third surface gate insulating film 23 is, for example, a silicon oxide film.

[0044] The back surface cell gate electrode 34 is provided in the cell region 100a. The back surface cell gate electrode 34 is provided on the second surface P2 side of the cell portion 10a. The first back surface gate electrode pad 104 is electrically connected to the back surface cell gate electrode 34 using wiring (not shown).

[0045] The back surface cell gate electrode 34 is, for example, polycrystalline silicon containing n-type impurities or p-type impurities. A fourth gate voltage (Vg4) is applied to the back surface cell gate electrode 34. The fourth gate voltage (Vg4) is a voltage based on the collector voltage (Vc).

[0046] Hereinafter, the transistor controlled by the fourth gate voltage (Vg4) applied to the back surface cell gate electrode 34 will be referred to as a back surface cell transistor.

[0047] The first back surface gate insulating film 24 is provided between the back surface cell gate electrode 34 and the cell portion 10a. The first back surface gate insulating film 24 is, for example, a silicon oxide film.

[0048] The back surface termination gate electrode 35 is provided in the termination region 100b. The back surface termination gate electrode 35 is provided on the second surface P2 side of the termination region 10b. The second back surface gate electrode pad 105 is electrically connected to the back surface termination gate electrode 35 using wiring (not shown).

[0049] The back surface termination gate electrode 35 is, for example, polycrystalline silicon containing n-type impurities or p-type impurities. A fifth gate voltage (Vg5) is applied to the back surface termination gate electrode 35. The fifth gate voltage (Vg5) is a voltage based on the collector voltage (Vc).

[0050] Hereinafter, the transistor controlled by the fifth gate voltage (Vg5) applied to the back surface termination gate electrode 35 will be referred to as a back surface termination transistor.

[0051] The second back surface gate insulating film 25 is provided between the back surface termination gate electrode 35 and the termination portion 10b. The second back surface gate insulating film 25 is, for example, a silicon oxide film.

[0052] 3A and 3B are schematic plan views of the semiconductor device of the first embodiment. Fig. 3A is a plan view of the front surface side of the IGBT 100, i.e., the first surface P1 side of the semiconductor layer 10. Fig. 3B is a plan view of the back surface side of the IGBT 100, i.e., the second surface P2 side of the semiconductor layer 10.

[0053] 3(a) is a diagram schematically showing the arrangement of the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33. FIG. 3(b) is a diagram schematically showing the arrangement of the back surface cell gate electrode 34 and the back surface termination gate electrode 35.

[0054] 3(a), the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33 are provided in the cell region 100a. The main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33 extend in a first direction.

[0055] 3(b), the back surface cell gate electrode 34 is provided in the cell region 100a. The back surface termination gate electrode 35 is provided in the termination region 100b. The back surface cell gate electrode 34 and the back surface termination gate electrode 35 extend in a first direction.

[0056] The surface interlayer insulating layer 40 is provided on the first face P1 side of the semiconductor layer 10. The surface interlayer insulating layer 40 is provided between a part of the semiconductor layer 10 and the emitter electrode 12. The surface interlayer insulating layer 40 electrically separates the part of the semiconductor layer 10 from the emitter electrode 12. The surface interlayer insulating layer 40 electrically separates the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33 from the emitter electrode 12.

[0057] The surface interlayer insulating layer 40 is, for example, silicon oxide.

[0058] The back surface interlayer insulating layer 42 is provided on the second surface P2 side of the semiconductor layer 10. The back surface interlayer insulating layer 42 is provided between a portion of the semiconductor layer 10 and the collector electrode 14. The back surface interlayer insulating layer 42 electrically separates the portion of the semiconductor layer 10 from the collector electrode 14. The back surface interlayer insulating layer 42 electrically separates the back surface cell gate electrode 34 and the back surface termination gate electrode 35 from the collector electrode 14.

[0059] The back surface interlayer insulating layer 42 is, for example, silicon oxide.

[0060] The p-type cell collector region 64 is provided in the cell portion 10a. The cell collector region 64 is provided in a portion between the drift region 68 and the second plane P2. A portion of the cell collector region 64 contacts the second plane P2.

[0061] A part of the cell collector region 64 faces the back surface cell gate electrode 34, with the first back surface gate insulating film 24 sandwiched therebetween. The cell collector region 64 extends in the first direction on the second plane P2. In the cell collector region 64 facing the back surface cell gate electrode 34, a channel of the back surface cell transistor controlled by the back surface cell gate electrode 34 is formed.

[0062] The cell collector region 64 is electrically connected to the collector electrode 14. A portion of the cell collector region 64 contacts the collector electrode 14.

[0063] A p-type termination collector region 65 is provided in termination portion 10b. Termination collector region 65 is provided partially between drift region 68 and second plane P2. A portion of termination collector region 65 contacts second plane P2.

[0064] A part of the termination collector region 65 faces the back surface termination gate electrode 35 with the second back surface gate insulating film 25 sandwiched therebetween. The termination collector region 65 extends in the first direction on the second plane P2. In the termination collector region 65 facing the back surface termination gate electrode 35, a channel of a back surface termination transistor controlled by the back surface termination gate electrode 35 is formed.

[0065] The termination collector region 65 is electrically connected to the collector electrode 14. A portion of the termination collector region 65 contacts the collector electrode 14.

[0066] The n-type cell drain region 60 is provided in the cell portion 10a. The cell drain region 60 is provided in a portion between the cell collector region 64 and the second surface P2. A portion of the cell collector region 64 faces the back surface cell gate electrode 34, with the first back surface gate insulating film 24 sandwiched therebetween.

[0067] A part of the cell drain region 60 contacts the collector electrode 14. The cell drain region 60 extends in a first direction. The cell drain region 60 functions as the drain of the back surface cell transistor.

[0068] The n-type impurity concentration of the cell drain region 60 is higher than the n-type impurity concentration of the drift region 68 .

[0069] The n-type termination drain region 62 is provided in the termination portion 10b. The termination drain region 62 is provided partially between the termination collector region 65 and the second surface P2. A portion of the termination drain region 62 faces the back surface termination gate electrode 35, with the second back surface gate insulating film 25 sandwiched therebetween.

[0070] A portion of the terminating drain region 62 contacts the collector electrode 14. The terminating drain region 62 extends in a first direction. The terminating drain region 62 functions as the drain of the back surface terminated transistor.

[0071] The n-type impurity concentration of the terminating drain region 62 is higher than the n-type impurity concentration of the drift region 68 .

[0072] The n-type drift region 68 is provided between the cell collector region 64 and the first plane P1. The drift region 68 is provided between the termination collector region 65 and the first plane P1. The drift region 68 is provided between the cell collector region 64 and the base region 70.

[0073] The drift region 68 serves as a path for an on-current when the IGBT 100 is in an on-state. The drift region 68 is depleted when the IGBT 100 is in an off-state, and has the function of maintaining the breakdown voltage of the IGBT 100.

[0074] The n-type buffer region 66 is provided between the drift region 68 and the cell collector region 64. The buffer region 66 is provided between the drift region 68 and the termination collector region 65.

[0075] A part of the buffer region 66 contacts the second plane P2. A part of the buffer region 66 faces the back surface cell gate electrode 34 with the first back surface gate insulating film 24 therebetween. A part of the buffer region 66 faces the back surface termination gate electrode 35 with the second back surface gate insulating film 25 therebetween.

[0076] The n-type impurity concentration of the buffer region 66 is higher than the n-type impurity concentration of the drift region 68 .

[0077] The buffer region 66 has a lower resistance than the drift region 68. By providing the buffer region 66, when the back surface cell transistor is turned on, the discharge of electrons from the drift region 68 to the collector electrode 14 via the back surface cell transistor is promoted. By providing the buffer region 66, when the back surface termination transistor is turned on, the discharge of electrons from the drift region 68 to the collector electrode 14 via the back surface termination transistor is promoted.

[0078] The buffer region 66 also has the function of suppressing the extension of the depletion layer when the IGBT 100 is in the off state. Note that it is also possible to configure the IGBT 100 without the buffer region 66.

[0079] The p-type base region 70 is provided in the cell region 100a. The base region 70 is provided in the cell portion 10a. The base region 70 is provided between the drift region 68 and the first plane P1.

[0080] A part of the base region 70 faces the main gate electrode 31 with the first surface gate insulating film 21 sandwiched therebetween. In the base region 70 facing the main gate electrode 31, a channel of the main gate transistor controlled by the main gate electrode 31 is formed.

[0081] A part of the base region 70 faces the control gate electrode 32 with the second surface gate insulating film 22 sandwiched therebetween. In the base region 70 facing the control gate electrode 32, a channel of the control gate transistor controlled by the control gate electrode 32 is formed.

[0082] A part of the base region 70 faces the pre-gate electrode 33 with the third surface gate insulating film 23 sandwiched therebetween. In the base region 70 facing the pre-gate electrode 33, a channel of a pre-gate transistor controlled by the pre-gate electrode 33 is formed.

[0083] The n-type emitter region 72 is provided in the cell region 100a. The emitter region 72 is provided in the cell portion 10a. The emitter region 72 is provided between the base region 70 and the first plane P1. The emitter region 72 extends in a first direction on the first plane P1.

[0084] A part of the emitter region 72 faces the main gate electrode 31 with the first surface gate insulating film 21 sandwiched therebetween. A part of the emitter region 72 contacts the main gate trench 51. A part of the emitter region 72 contacts the first surface gate insulating film 21.

[0085] A part of the emitter region 72 faces the control gate electrode 32 with the second surface gate insulating film 22 sandwiched therebetween. A part of the emitter region 72 contacts the control gate trench 52. A part of the emitter region 72 contacts the second surface gate insulating film 22.

[0086] A part of the emitter region 72 faces the pre-gate electrode 33 with the third surface gate insulating film 23 sandwiched therebetween. A part of the emitter region 72 contacts the pre-gate trench 53. A part of the emitter region 72 contacts the third surface gate insulating film 23.

[0087] The emitter region 72 is electrically connected to the emitter electrode 12. A part of the emitter region 72 contacts the emitter electrode 12.

[0088] The n-type impurity concentration of the emitter region 72 is higher than the n-type impurity concentration of the drift region 68. The emitter region 72 serves as a source of electrons when the IGBT 100 is in the on state.

[0089] The p-type contact region 74 is provided in the cell region 100a. The contact region 74 is provided in the cell portion 10a. The contact region 74 is provided between the base region 70 and the first face P1. The contact region 74 extends in a first direction on the first face P1.

[0090] The contact region 74 is electrically connected to the emitter electrode 12. The contact region 74 contacts the emitter electrode 12.

[0091] The p-type impurity concentration of the contact region 74 is higher than the p-type impurity concentration of the base region 70 .

[0092] The p-type boundary region 76 is provided in the termination region 100b. The boundary region 76 is provided in the termination portion 10b. The boundary region 76 is provided between the drift region 68 and the first plane P1. The boundary region 76 surrounds the cell portion 10a.

[0093] A p-type guard ring region 78 is provided in the termination region 100b. The guard ring region 78 is provided in the termination portion 10b. The guard ring region 78 is provided between the drift region 68 and the first plane P1. The guard ring region 78 surrounds the cell portion 10a. For example, a plurality of guard ring regions 78 may be provided.

[0094] By providing the boundary region 76 and the guard ring region 78, the electric field strength at the end of the cell region 100a is reduced, and a decrease in the breakdown voltage when the IGBT 100 is in the off state is suppressed.

[0095] The control circuit 150 controls the IGBT 100. The control circuit 150 is, for example, a gate driver circuit. The gate driver circuit independently controls the magnitude and timing of voltages applied to the first front gate electrode pad 101, the second front gate electrode pad 102, the third front gate electrode pad 103, the first back gate electrode pad 104, and the second back gate electrode pad 105.

[0096] The control circuit 150 independently controls a first gate voltage (Vg1) applied to the main gate electrode 31, a second gate voltage (Vg2) applied to the control gate electrode 32, a third gate voltage (Vg3) applied to the pre-gate electrode 33, a fourth gate voltage (Vg4) applied to the back surface cell gate electrode 34, and a fifth gate voltage (Vg5) applied to the back surface termination gate electrode 35.

[0097] Next, the operation of the IGBT 100 will be described.

[0098] 4 is a timing chart of the semiconductor device of the first embodiment, showing the timing of changes in the first gate voltage (Vg1), the second gate voltage (Vg2), the third gate voltage (Vg3), the fourth gate voltage (Vg4), and the fifth gate voltage (Vg5).

[0099] The first gate voltage (Vg1) is the gate voltage applied to the main gate transistor controlled by the main gate electrode 31. The second gate voltage (Vg2) is the gate voltage applied to the control gate transistor controlled by the control gate electrode 32. The third gate voltage (Vg3) is the gate voltage applied to the pre-gate transistor controlled by the pre-gate electrode 33. The fourth gate voltage (Vg4) is the gate voltage applied to the backside cell transistor controlled by the backside cell gate electrode 34. The fifth gate voltage (Vg5) is the gate voltage applied to the backside termination transistor controlled by the backside termination gate electrode 35.

[0100] When the IGBT 100 is in an off state, an emitter voltage (Ve) is applied to the emitter electrode 12. For example, at time t0, the emitter voltage (Ve) is applied to the emitter electrode 12. The emitter voltage (Ve) is, for example, 0 V.

[0101] When the IGBT 100 is in an off state, a collector voltage (Vc) is applied to the collector electrode 14. The collector voltage (Vc) is, for example, not less than 200 V and not more than 6500 V. The collector-emitter voltage (Vce) applied between the collector electrode 14 and the emitter electrode 12 is, for example, not less than 200 V and not more than 6500 V.

[0102] The first gate voltage (Vg1), the second gate voltage (Vg2), and the third gate voltage (Vg3) are voltages based on the emitter voltage (Ve), and the fourth gate voltage (Vg4) and the fifth gate voltage (Vg5) are voltages based on the collector voltage (Vc).

[0103] First, the timing of change in the first gate voltage (Vg1) applied to the main gate transistor will be described.

[0104] For example, at time t0, a first turn-off voltage (Voff1) is applied as the first gate voltage (Vg1). The first turn-off voltage (Voff1) is a voltage equal to or lower than the threshold voltage at which the main gate transistor does not turn on.

[0105] The first turn-off voltage (Voff1) is, for example, 0 V or a negative voltage. Fig. 4 illustrates an example in which the first turn-off voltage (Voff1) is -15 V.

[0106] At time t1, a first turn-on voltage (Von1) is applied as a first gate voltage (Vg1). The first turn-on voltage (Von1) is a positive voltage that exceeds the threshold voltage of the main gate transistor. Figure 4 illustrates an example in which the first turn-on voltage (Von1) is 15V.

[0107] The first turn-on voltage (Von1) is applied to the main gate transistor, turning on the IGBT 100. The IGBT 100 is turned on at time t1.

[0108] By applying a first turn-on voltage (Von1) to the main gate transistor, an n-type inversion layer is formed in the p-type base region 70 near the interface with the first surface gate insulating film 21. The formation of the n-type inversion layer causes electrons to be injected from the n-type emitter region 72 through the n-type inversion layer into the n-type drift region 68. The electrons injected into the n-type drift region 68 forward bias the pn junctions formed between the n-type buffer region 66 and the p-type cell collector region 64, and between the n-type buffer region 66 and the p-type termination collector region 65. The electrons reach the collector electrode 14 and cause holes to be injected from the p-type cell collector region 64 and the p-type termination collector region 65. This turns the IGBT 100 on.

[0109] At time t4, a first turn-off voltage (Voff1) is applied as a first gate voltage (Vg1). By applying the first turn-off voltage (Voff1) to the main gate transistor, the IGBT 100 is turned off. Between time t1 and time t4, the IGBT 100 is in an on state.

[0110] Next, the timing of change in the second gate voltage (Vg2) applied to the control gate transistor will be described.

[0111] For example, at time t0, a second turn-off voltage (Voff2) is applied as the second gate voltage (Vg2). The second turn-off voltage (Voff2) is a voltage equal to or lower than the threshold voltage at which the control gate transistor does not turn on.

[0112] The second turn-off voltage (Voff2) is, for example, a negative voltage. Figure 4 illustrates an example in which the second turn-off voltage (Voff2) is -15V.

[0113] At time t1, a second turn-on voltage (Von2) is applied as a second gate voltage (Vg2). The second turn-on voltage (Von2) is a positive voltage that exceeds the threshold voltage of the control gate transistor. Figure 4 illustrates an example in which the second turn-on voltage (Von2) is 15V.

[0114] By applying a second turn-on voltage (Von2) to the control gate transistor, an n-type inversion layer is formed in the p-type base region 70 near the interface with the second surface gate insulating film 22. By forming the n-type inversion layer, electrons are injected from the n-type emitter region 72 into the n-type drift region 68 through the n-type inversion layer.

[0115] At time t3 prior to time t4, a second turn-off voltage (Voff2) is applied as a second gate voltage (Vg2). By applying the second turn-off voltage (Voff2) to the control gate transistor, injection of electrons into the drift region 68 via the control gate transistor is blocked. Furthermore, by setting the second gate voltage (Vg2) to a negative voltage, a p-type accumulation layer is formed in the p-type base region 70 near the control gate trench 52. The formation of the p-type accumulation layer promotes the discharge of holes to the emitter electrode 12. Therefore, the number of carriers in the drift region 68 decreases.

[0116] Next, the timing of change in the third gate voltage (Vg3) applied to the pre-gate transistor will be described.

[0117] For example, at time t0, a third turn-off voltage (Voff3) is applied as the third gate voltage (Vg3). The third turn-off voltage (Voff3) is a voltage equal to or lower than the threshold voltage at which the pre-gate transistor does not turn on.

[0118] The third turn-off voltage (Voff3) is, for example, 0 V or a negative voltage. Fig. 4 illustrates an example in which the third turn-off voltage (Voff3) is 0 V.

[0119] At time t1, a third turn-on voltage (Von3) is applied as a third gate voltage (Vg3). The third turn-on voltage (Von3) is a positive voltage that exceeds the threshold voltage of the pre-gate transistor. Figure 4 illustrates an example where the third turn-on voltage (Von3) is 15V.

[0120] Applying a third turn-on voltage (Von3) to the pre-gate transistor turns the pre-gate transistor on. Applying the third turn-on voltage (Von3) to the pre-gate transistor forms an n-type inversion layer near the interface between the p-type base region 70 and the third surface gate insulating film 23. As the n-type inversion layer is formed, electrons are injected from the n-type emitter region 72 through the n-type inversion layer into the n-type drift region 68.

[0121] At time t2 prior to time t3, a third turn-off voltage (Voff3) is applied as a third gate voltage (Vg3). By applying the third turn-off voltage (Voff3) to the pre-gate transistor, the pre-gate transistor is turned off. By turning the pre-gate transistor off, injection of electrons into the drift region 68 via the pre-gate transistor is blocked. Therefore, the number of electrons injected into the drift region 68 is reduced.

[0122] For example, a negative voltage may be applied as the third gate voltage (Vg3) at time t3. By applying a negative voltage as the third gate voltage (Vg3), a p-type accumulation layer is formed in the p-type base region 70 near the pre-gate trench 53. The formation of the p-type accumulation layer promotes the discharge of holes to the emitter electrode 12. Therefore, the number of carriers in the drift region 68 decreases.

[0123] Next, the timing of change in the fourth gate voltage (Vg4) applied to the back surface cell transistor will be described.

[0124] For example, at time t0, a fourth turn-off voltage (Voff4) is applied as the fourth gate voltage (Vg4). The fourth turn-off voltage (Voff4) is a voltage equal to or lower than the threshold voltage at which the back surface cell transistor does not turn on.

[0125] The fourth turn-off voltage (Voff4) is, for example, 0 V or a negative voltage. Fig. 4 illustrates an example in which the fourth turn-off voltage (Voff4) is 0 V.

[0126] At time ty, a fourth turn-on voltage (Von4) is applied as a fourth gate voltage (Vg4). The fourth turn-on voltage (Von4) is a positive voltage that exceeds the threshold voltage of the backside cell transistor. Figure 4 illustrates an example in which the fourth turn-on voltage (Von4) is 15V.

[0127] By applying a fourth turn-on voltage (Von4) to the back surface cell transistor, an n-type inversion layer is formed in the vicinity of the interface between the p-type cell collector region 64 and the first back surface gate insulating film 24.

[0128] The formation of an n-type inversion layer near the interface between the p-type cell collector region 64 and the first back surface gate insulating film 24 forms a path for electrons to be discharged from the n-type buffer region 66 of the cell portion 10a through the n-type inversion layer and the n-type cell drain region 60 to the collector electrode 14. In other words, a so-called anode short occurs, which is a state in which the n-type buffer region 66 of the cell portion 10a and the collector electrode 14 are short-circuited.

[0129] The anode short prevents electrons from passing from the n-type buffer region 66 of the cell portion 10a through the p-type cell collector region 64 to the collector electrode 14. This prevents holes from being injected from the p-type cell collector region 64 into the drift region 68 of the cell portion 10a.

[0130] After that, at time t5, a fourth turn-off voltage (Voff4) is applied as a fourth gate voltage (Vg4) to turn off the back cell transistor.

[0131] Next, the timing of change in the fifth gate voltage (Vg5) applied to the back surface termination transistor will be described.

[0132] For example, at time t0, a fifth turn-off voltage (Voff5) is applied as a fifth gate voltage (Vg5). The fifth turn-off voltage (Voff5) is a voltage equal to or lower than the threshold voltage at which the backside termination transistor does not turn on.

[0133] The fifth turn-off voltage (Voff5) is, for example, 0 V or a negative voltage. Fig. 4 illustrates an example in which the fifth turn-off voltage (Voff5) is 0 V.

[0134] At time tx prior to time ty, a fifth turn-on voltage (Von5) is applied as a fifth gate voltage (Vg5). The fifth turn-on voltage (Von5) is a positive voltage that exceeds the threshold voltage of the backside termination transistor. Figure 4 illustrates an example where the fifth turn-on voltage (Von5) is 15V.

[0135] By applying a fifth turn-on voltage (Von5) to the back surface termination transistor, an n-type inversion layer is formed in the vicinity of the interface between the p-type termination collector region 65 and the second back surface gate insulating film 25.

[0136] The formation of an n-type inversion layer near the interface between the p-type termination collector region 65 and the second back surface gate insulating film 25 forms a path for electrons to be emitted from the n-type buffer region 66 of the termination portion 10b through the n-type inversion layer and the n-type termination drain region 62 to the collector electrode 14. In other words, a so-called anode short occurs, which is a state in which the buffer region 66 of the n-type termination portion 10b and the collector electrode 14 are short-circuited.

[0137] The anode short prevents electrons from passing from the n-type buffer region 66 of the termination portion 10b through the p-type termination collector region 65 to the collector electrode 14. This prevents holes from being injected from the p-type termination collector region 65 into the drift region 68 of the termination portion 10b.

[0138] Note that time tx may be before time t3 or after time t3, and may be before time t4 or after time t4.

[0139] Then, at time t5, a fifth turn-off voltage (Voff5) is applied as a fifth gate voltage (Vg5) to turn off the backside termination transistor.

[0140] The control circuit 150 controls the magnitude and timing of a first gate voltage (Vg1) applied to the first front gate electrode pad 101, a second gate voltage (Vg2) applied to the second front gate electrode pad 102, a third gate voltage (Vg3) applied to the third front gate electrode pad 103, a fourth gate voltage (Vg4) applied to the first back gate electrode pad 104, and a fifth gate voltage (Vg5) applied to the second back gate electrode pad 105, thereby realizing the operation of the IGBT 100.

[0141] For example, the control circuit 150 applies a first turn-on voltage (Von1) to the first front surface gate electrode pad 101 at time t1, a second turn-on voltage (Von2) to the second front surface gate electrode pad 102 at time t1, and a third turn-on voltage (Von3) to the third front surface gate electrode pad 103 at time t1. Thereafter, at time t2 after a predetermined time has elapsed since time t1, the control circuit 150 applies a third turn-off voltage (Voff3) to the third front surface gate electrode pad 103. Then, at time tx after a predetermined time has elapsed since time t2, the control circuit 150 applies a fifth turn-on voltage (Von5) to the second back surface gate electrode pad 105. Then, at time ty after a predetermined time has elapsed since time tx, the control circuit 150 applies a fourth turn-on voltage (Von4) to the first back surface gate electrode pad 104.

[0142] For example, the control circuit 150 applies a third turn-on voltage (Von3) to the third front surface gate electrode pad 103 at time t1, and then applies a first turn-off voltage (Voff1) to the first front surface gate electrode pad 101 at time t4 after a predetermined time has elapsed. Then, at time tx before time t4, the control circuit 150 applies a fifth turn-on voltage (Von5) to the second back surface gate electrode pad 105.

[0143] Next, the operation and effects of the semiconductor device of the first embodiment will be described.

[0144] The IGBT 100 of the first embodiment includes a control gate transistor on the surface side of the semiconductor layer 10 that can be controlled independently of the main gate transistor. At time t3, before time t4 when the IGBT 100 is turned off, a negative voltage is applied to the gate electrode of the control gate transistor to turn it off, thereby promoting the discharge of holes to the emitter electrode 12. Therefore, compared to a case where the control gate transistor is not provided, the number of carriers that need to be discharged during the turn-off operation of the IGBT 100 can be reduced. This reduces the turn-off loss of the IGBT 100.

[0145] For example, by applying a negative voltage to the gate electrode of the pre-gate transistor at time t3, the amount of carriers to be discharged during the turn-off operation can be further reduced, thereby further reducing the turn-off loss of the IGBT 100.

[0146] The IGBT 100 of the first embodiment also includes a pre-transistor on the surface side of the semiconductor layer 10 that can be controlled independently of the main gate transistor and the control gate transistor. By turning on the pre-transistor at time t1 when the IGBT 100 turns on, the amount of electrons injected into the drift region 68 increases compared to when the pre-transistor is not provided. This reduces the turn-on time of the IGBT 100 compared to when the pre-transistor is not provided. This reduces the turn-on loss of the IGBT 100.

[0147] Then, at time t2, before time t4 when the IGBT 100 is turned off, the pre-transistor is turned off. By turning off the pre-transistor, the saturation current of the IGBT 100 is reduced. Therefore, it is possible to prevent the IGBT 100 from being destroyed when, for example, a load short circuit occurs and a large current flows through the IGBT 100.

[0148] The IGBT 100 of the first embodiment also includes a backside cell transistor on the backside of the semiconductor layer 10. When the IGBT 100 is turned off, the backside cell transistor is turned on to suppress hole injection into the drift region 68 of the cell unit 10a. By suppressing hole injection into the drift region 68, turn-off loss is reduced compared to when the IGBT 100 does not include a backside cell transistor. This allows for a reduction in power consumption of the IGBT 100.

[0149] Furthermore, the IGBT 100 of the first embodiment is provided with a termination region 100b around the cell region 100a. The termination region 100b is provided with a boundary region 76 and a guard ring region 78. By providing the boundary region 76 and the guard ring region 78, the electric field strength at the end of the cell region 100a is reduced, and a reduction in the breakdown voltage when the IGBT 100 is in the off state is suppressed.

[0150] When the IGBT 100 is in the on state, an on-current also flows between the emitter electrode 12 and the collector electrode 14 of the termination region 100b. Therefore, when the IGBT 100 is in the on state, carriers also accumulate in the drift region 68 of the termination region 100b. In other words, when the IGBT 100 is in the on state, carriers spread to the termination region 100b, where no transistors exist on the surface.

[0151] When the IGBT 100 is turned off, the carriers accumulated in the drift region 68 of the termination region 10b must be discharged. However, there is no carrier discharge path on the surface side of the termination region 100b. As a result, the carriers are concentrated and discharged at the edge of the cell region 100a. This causes current concentration at the edge of the cell region 100a. This current concentration may cause damage to the IGBT 100.

[0152] The IGBT 100 of the first embodiment includes a back surface termination transistor that can be controlled independently of the back surface cell transistor, on the back surface side of the semiconductor layer 10 in the termination region 100b. The back surface termination transistor is turned on at time tx, which is before time ty, when the back surface cell transistor is turned on. By turning on the back surface termination transistor, hole injection into the n-type drift region 68 in the termination portion 10b is suppressed.

[0153] By turning on the back surface termination transistor before the back surface cell transistor, it is possible to selectively reduce the carriers accumulated in the drift region 68 of the termination section 10b. This prevents current concentration at the end of the cell region 100a when the IGBT 100 is turned off. This prevents the IGBT 100 from being destroyed by current concentration.

[0154] From the viewpoint of suppressing destruction of the IGBT 100 due to current concentration, it is preferable to turn on the back surface termination transistor before the turn-off operation of the IGBT 100. In other words, it is preferable to turn on the back surface termination transistor before time t4 when the IGBT 100 turns off. In other words, it is preferable that time tx is before time t4. In other words, it is preferable to apply the fifth turn-on voltage (Von5) to the second back surface gate electrode pad 105 before applying the first turn-off voltage (Voff1) to the first front surface gate electrode pad 101.

[0155] As described above, according to the first embodiment, it is possible to realize a semiconductor device and a semiconductor circuit in which turn-off loss is reduced and breakdown due to current concentration is suppressed.

[0156] (Second embodiment) The semiconductor device and semiconductor circuit of the second embodiment differ from the semiconductor device and semiconductor circuit of the first embodiment in that the first gate electrode extends in a first direction parallel to the first surface, the fourth gate electrode extends in a second direction parallel to the first surface and perpendicular to the first direction, and the fifth gate electrode extends in a direction perpendicular to the fourth gate electrode. Hereinafter, some description of content that overlaps with the first embodiment may be omitted.

[0157] The semiconductor device of the second embodiment is an IGBT 200 with a double-sided gate structure, similar to the first embodiment, having gate electrodes on the front and back sides of the semiconductor layer. The IGBT 200 also has three independently controlled gate electrodes on the front side of the semiconductor layer. The IGBT 200 also has two independently controlled gate electrodes on the back side of the semiconductor layer.

[0158] 5A and 5B are schematic plan views of a semiconductor device according to a second embodiment. Fig. 5A is a plan view of the front surface of the IGBT 200, i.e., viewed from the first surface P1 of the semiconductor layer 10. Fig. 5B is a plan view of the back surface of the IGBT 200, i.e., viewed from the second surface P2 of the semiconductor layer 10.

[0159] 5(a) is a diagram schematically showing the arrangement of the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33. FIG. 5(b) is a diagram schematically showing the arrangement of the back surface cell gate electrode 34 and the back surface termination gate electrode 35.

[0160] The IGBT 200 has a cell region 100a, a termination region 100b, a first front surface gate electrode pad 101 (first electrode pad), a second front surface gate electrode pad 102 (second electrode pad), a third front surface gate electrode pad 103 (third electrode pad), a first back surface gate electrode pad 104 (fourth electrode pad), and a second back surface gate electrode pad 105 (fifth electrode pad).

[0161] The termination region 100b surrounds the cell region 100a. A first front surface gate electrode pad 101, a second front surface gate electrode pad 102, and a third front surface gate electrode pad 103 are located on the front surface side of the IGBT 200. In addition, a first back surface gate electrode pad 104 and a second back surface gate electrode pad 105 are located on the back surface side of the IGBT 200.

[0162] 5(a), the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33 are provided in the cell region 100a. The main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33 extend in a first direction in the cell region 100a.

[0163] 5(b), the back surface cell gate electrode 34 is provided in the cell region 100a. The back surface cell gate electrode 34 extends in a second direction perpendicular to the first direction.

[0164] The back surface termination gate electrode 35 is provided in the termination region 100b. The back surface termination gate electrode 35 extends in a first direction perpendicular to the second direction. The back surface termination gate electrode 35 extends in a direction perpendicular to the back surface cell gate electrode 34.

[0165] The back surface cell gate electrode 34 extends in a direction perpendicular to the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33, thereby making the flow of the on-current of the IGBT 200 uniform. This makes it difficult for local on-current concentration to occur. This prevents the IGBT 200 from being destroyed by current concentration.

[0166] As described above, according to the second embodiment, it is possible to realize a semiconductor device and a semiconductor circuit in which turn-off loss is reduced and breakdown due to current concentration is suppressed.

[0167] (Third embodiment) The semiconductor device and semiconductor circuit of the third embodiment differ from the semiconductor device and semiconductor circuit of the first embodiment in that the third semiconductor region and the second trench are spaced apart. Hereinafter, some of the description overlapping with the first embodiment may be omitted.

[0168] The semiconductor device of the third embodiment is an IGBT 300 with a double-sided gate structure, similar to the first embodiment, having gate electrodes on both the front and back sides of the semiconductor layer. The IGBT 300 also has three independently controlled gate electrodes on the front side of the semiconductor layer. The IGBT 300 also has two independently controlled gate electrodes on the back side of the semiconductor layer.

[0169] Fig. 6 is a schematic cross-sectional view of a part of a semiconductor device according to the third embodiment, which corresponds to Fig. 2 of the first embodiment.

[0170] The IGBT 300 of the third embodiment includes a semiconductor layer 10, an emitter electrode 12 (first electrode), a collector electrode 14 (second electrode), a first front surface gate insulating film 21, a second front surface gate insulating film 22, a third front surface gate insulating film 23, a first rear surface gate insulating film 24, a second rear surface gate insulating film 25, a main gate electrode 31 (first gate electrode), a control gate electrode 32 (second gate electrode), a pre-gate electrode 33 (third gate electrode), a rear surface cell gate electrode 34 (fourth gate electrode), a rear surface termination gate electrode 35 (fifth gate electrode), a front surface interlayer insulating layer 40, and a rear surface interlayer insulating layer 42.

[0171] The semiconductor layer 10 includes a main gate trench 51 (first trench), a control gate trench 52 (second trench), a pre-gate trench 53 (third trench), an n-type cell drain region 60 (sixth semiconductor region), an n-type termination drain region 62 (seventh semiconductor region), a p-type cell collector region 64 (fourth semiconductor region), a p-type termination collector region 65 (fifth semiconductor region), an n-type buffer region 66, an n-type drift region 68 (first semiconductor region), a p-type base region 70 (second semiconductor region), an n-type emitter region 72 (third semiconductor region), a p-type contact region 74, a p-type boundary region 76, and a p-type guard ring region 78.

[0172] The emitter region 72 is spaced apart from the control gate trench 52. The emitter region 72 does not contact the control gate trench 52.

[0173] The emitter region 72 is separated from the second surface gate insulating film 22. The emitter region 72 does not contact the second surface gate insulating film 22.

[0174] 7 is a timing chart of the semiconductor device of the third embodiment, showing the timing of changes in the first gate voltage (Vg1), the second gate voltage (Vg2), the third gate voltage (Vg3), the fourth gate voltage (Vg4), and the fifth gate voltage (Vg5).

[0175] 7 differs from the timing chart of the first embodiment shown in FIG. 4 only in the change timing of the second gate voltage (Vg2) applied to the control gate electrode 32. Therefore, only the timing of the second gate voltage (Vg2) will be described.

[0176] Note that even if the second gate voltage (Vg2) applied to the control gate electrode 32 is changed, the transistor operation does not occur because the emitter region 72 is not in contact with the control gate trench 52. However, for the sake of consistency with the description of the first embodiment, the terms second turn-on voltage (Von2) and second turn-off voltage (Voff2) will be used hereinafter.

[0177] For example, at time t0, a second turn-on voltage (Von2) is applied as the second gate voltage (Vg2). The second turn-on voltage (Von2) is a voltage higher than the voltage at which a p-type accumulation layer is formed in the p-type base region 70 near the control gate trench 52.

[0178] The second turn-on voltage (Von2) is, for example, 0 V or a positive voltage. Fig. 7 illustrates a case where the second turn-on voltage (Von2) is 0 V.

[0179] At time t3 prior to time t4, a second turn-off voltage (Voff2) is applied as the second gate voltage (Vg2). The second turn-off voltage (Voff2) is a voltage equal to or lower than the voltage at which a p-type accumulation layer is formed in the p-type base region 70 near the control gate trench 52. The second turn-off voltage (Voff2) is a negative voltage. FIG. 7 illustrates an example in which the second turn-off voltage (Voff2) is −15 V.

[0180] When a second turn-off voltage (Voff2) is applied to the control gate transistor, a p-type accumulation layer is formed in the p-type base region 70 near the control gate trench 52. The formation of the p-type accumulation layer promotes the discharge of holes to the emitter electrode 12. Therefore, the number of carriers in the drift region 68 decreases.

[0181] After that, at time t5, the second turn-on voltage (Von2) is applied as the second gate voltage (Vg2) to eliminate the p-type accumulation layer.

[0182] The IGBT 300 of the third embodiment does not operate as a transistor even when the second gate voltage (Vg2) applied to the control gate electrode 32 is changed. Therefore, the operation of the IGBT 300 is more stable than that of the IGBT 100.

[0183] Furthermore, the absence of the emitter region 72 in contact with the control gate trench 52 promotes the discharge of holes to the emitter electrode 12 compared to when the emitter region 72 is present. Therefore, the turn-off loss is further reduced compared to the IGBT 100.

[0184] As described above, according to the third embodiment, it is possible to realize a semiconductor device and a semiconductor circuit in which turn-off loss is reduced and breakdown due to current concentration is suppressed.

[0185] In the first to third embodiments, the semiconductor layer is made of single crystal silicon, but the semiconductor layer is not limited to single crystal silicon. For example, the semiconductor layer may be made of other single crystal semiconductors such as single crystal silicon carbide.

[0186] In the first to third embodiments, the main gate electrode 31, the control gate electrode 32, the pre-gate electrode 33, the back surface cell gate electrode 34, and the back surface termination gate electrode 35 are all stripe-shaped. However, the shapes of the main gate electrode 31, the control gate electrode 32, the pre-gate electrode 33, the back surface cell gate electrode 34, and the back surface termination gate electrode 35 are not limited to stripe-shaped. For example, any or all of the main gate electrode 31, the control gate electrode 32, the pre-gate electrode 33, the back surface cell gate electrode 34, and the back surface termination gate electrode 35 may be polygonal or have a shape other than stripe-shaped.

[0187] In the first to third embodiments, an example has been described in which three types of gate electrodes, namely, the main gate electrode 31, the control gate electrode 32, and the pre-gate electrode 33, are provided on the surface side of the semiconductor layer 10. However, in addition to the above three types of gate electrodes, a dummy gate electrode may also be provided. The dummy gate electrode is, for example, a gate electrode in a trench whose potential is fixed to the potential of the emitter electrode 12.

[0188] In the first to third embodiments, the back surface cell transistor and the back surface termination transistor are described as planar gate type transistors, but either or both of the back surface cell transistor and the back surface termination transistor may be trench gate type transistors.

[0189] In the first to third embodiments, the first conductivity type is n-type and the second conductivity type is p-type, but it is also possible for the first conductivity type to be p-type and the second conductivity type to be n-type.

[0190] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or changed with components of another embodiment. These embodiments and modifications thereof are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0191] 10 Semiconductor layer 10a Cell section 10b Termination section 12 Emitter electrode (first electrode) 14 Collector electrode (second electrode) 31 main gate electrode (first gate electrode) 32 control gate electrode (second gate electrode) 33 Pre-gate electrode (third gate electrode) 34 rear cell gate electrode (fourth gate electrode) 35 Back surface termination gate electrode (fifth gate electrode) 51 Main Gate Trench (First Trench) 52 Control gate trench (second trench) 53 Pre-gate trench (third trench) 60 Cell drain region (sixth semiconductor region) 62 Termination drain region (seventh semiconductor region) 64 Cell collector region (fourth semiconductor region) 65 Termination collector region (fifth semiconductor region) 68 drift region (first semiconductor region) 70 base region (second semiconductor region) 72 emitter region (third semiconductor region) 100 IGBT (semiconductor device) 101 First surface gate electrode pad (first electrode pad) 102 Second surface gate electrode pad (second electrode pad) 103 Third surface gate electrode pad (third electrode pad) 104 First back gate electrode pad (fourth electrode pad) 105 Second rear gate electrode pad (fifth electrode pad) 150 control circuit 200 IGBT (semiconductor device) 300 IGBT (semiconductor device) 1000 Semiconductor modules (semiconductor circuits) P1 First side P2 Second side

Claims

1. A semiconductor layer having a first surface and a second surface opposite to the first surface, a first trench provided on the first surface side; a second trench provided on the first surface side; a semiconductor layer comprising: a first gate electrode disposed in the first trench; a second gate electrode disposed in the second trench; a fourth gate electrode provided on the second surface side; a fifth gate electrode provided on the second surface side; a first electrode in contact with the first surface; a second electrode in contact with the second surface; a first electrode pad electrically connected to the first gate electrode; a second electrode pad electrically connected to the second gate electrode; a fourth electrode pad electrically connected to the fourth gate electrode; a fifth electrode pad electrically connected to the fifth gate electrode.

2. the semiconductor layer has a cell portion and a termination portion surrounding the cell portion, the first trench and the second trench are provided on the first surface side of the cell portion, the fourth gate electrode is provided on the second surface side of the cell portion, 2. The semiconductor device according to claim 1, wherein said fifth gate electrode is provided on said second surface side of said terminal portion.

3. A semiconductor layer having a first surface and a second surface opposite to the first surface, a semiconductor layer including a first trench provided on the first surface side; a first gate electrode disposed in the first trench; a fourth gate electrode provided on the second surface side; a fifth gate electrode provided on the second surface side; a first electrode in contact with the first surface; a second electrode in contact with the second surface; a first electrode pad electrically connected to the first gate electrode; a fourth electrode pad electrically connected to the fourth gate electrode; a fifth electrode pad electrically connected to the fifth gate electrode; Equipped with the semiconductor layer has a cell portion and a termination portion surrounding the cell portion, The semiconductor layer is a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type provided between the first semiconductor region and the first surface in the cell portion and facing the first gate electrode; a third semiconductor region of the first conductivity type provided between the second semiconductor region and the first surface of the cell portion, in contact with the first electrode and in contact with the first trench; a fourth semiconductor region of the second conductivity type provided between the first semiconductor region and the second surface, facing the fourth gate electrode and in contact with the second electrode; a fifth semiconductor region of the second conductivity type provided between the first semiconductor region and the second surface, facing the fifth gate electrode and in contact with the second electrode; a sixth semiconductor region of the first conductivity type provided between the fourth semiconductor region and the second surface and in contact with the second electrode; a seventh semiconductor region of the first conductivity type provided between the fifth semiconductor region and the second surface and in contact with the second electrode; an eighth semiconductor region of a second conductivity type provided between the first semiconductor region and the first surface of the termination portion.

4. the first trench is provided in the cell portion, the fourth gate electrode is provided on the second surface side of the cell portion, 4. The semiconductor device according to claim 3, wherein said fifth gate electrode is provided on said second surface side of said terminal portion.

5. a second gate electrode provided in a second trench provided on the first surface side of the semiconductor layer; a second electrode pad electrically connected to the second gate electrode; The semiconductor device according to claim 3 , further comprising:

6. turning off a transistor controlled by a second gate voltage applied to the second gate electrode at a time before turning off a transistor controlled by a first gate voltage applied to the first gate electrode; turning on a transistor controlled by a fourth gate voltage applied to the fourth gate electrode at a time before turning off a transistor controlled by the first gate voltage applied to the first gate electrode; 6. The semiconductor device according to claim 1, wherein a transistor controlled by a fifth gate voltage applied to the fifth gate electrode is turned on at a time before a transistor controlled by the fourth gate voltage applied to the fourth gate electrode is turned on.

7. the first electrode pad and the second electrode pad are provided on the first surface side of the semiconductor layer, 6. The semiconductor device according to claim 1, wherein the fourth electrode pad and the fifth electrode pad are provided on the second surface side of the semiconductor layer.

8. A semiconductor device according to any one of claims 1, 2, and 5; a semiconductor circuit including a control circuit that controls voltages applied to the first electrode pad, the second electrode pad, the fourth electrode pad, and the fifth electrode pad;

9. The control circuit applying a first turn-on voltage to the first electrode pad, and after applying the first turn-on voltage to the first electrode pad, applying a first turn-off voltage to the first electrode pad; applying a second turn-on voltage to the second electrode pad, and applying a second turn-off voltage to the second electrode pad after applying the second turn-on voltage to the second electrode pad and before applying the first turn-off voltage to the first electrode pad; applying the first turn-on voltage to the first electrode pad, applying the second turn-on voltage to the second electrode pad, and then applying a third turn-on voltage to the fourth electrode pad before applying the first turn-off voltage to the first electrode pad; 9. The semiconductor circuit according to claim 8, wherein after the first turn-on voltage is applied to the first electrode pad, the second turn-on voltage is applied to the second electrode pad, and before the third turn-on voltage is applied to the fourth electrode pad, a fourth turn-on voltage is applied to the fifth electrode pad.

10. a third gate electrode provided in a third trench provided on the first surface side of the semiconductor layer; a third electrode pad electrically connected to the third gate electrode; The semiconductor device according to claim 1 , further comprising:

11. 6. The semiconductor device according to claim 1, wherein the fourth gate electrode and the fifth gate electrode are of a planar gate type.

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