Semiconductor device

Abstract

To provide a semiconductor device that can facilitate adjustment of a saturation voltage and suppress variation in characteristics.SOLUTION: A semiconductor device 100 includes: an N-type semiconductor substrate 10 having a first main surface 10A and a second main surface 10B on the opposite side of the first main surface; a first trench 21 and a second trench 22 provided on the first main surface; a P-type first semiconductor layer 11 provided on the first main surface between the first trench and the second trench; an N-type second semiconductor layer 12 provided at a position sandwiching the first trench between itself and the first semiconductor layer on the first main surface, and contacting the first trench; a P-type third semiconductor layer 13 provided under the second semiconductor layer, and contacting the second semiconductor layer and the first trench; an N-type fourth semiconductor layer 14 provided under the third semiconductor layer, contacting the third semiconductor layer, and separated from the first trench; and a P-type fifth semiconductor layer 15 provided at a position sandwiching the second trench between itself and the first semiconductor layer on the first main surface.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A semiconductor device is known in which a high-concentration N-type semiconductor layer is provided below a P-type channel region in an insulated gate bipolar transistor (IGBT) so as to be in contact with the entire lower surface of the channel region (Patent Document 1). By providing a high-concentration N-type semiconductor layer, the saturation voltage can be reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3288218 [Patent Document 2] Patent No. 5089191 Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional semiconductor device having a high-concentration N-type semiconductor layer, the characteristics such as the threshold voltage of the MOS structure of the IGBT tend to vary.

[0005] An object of the present disclosure is to provide a semiconductor device in which the saturation voltage can be easily adjusted and the variation in characteristics can be suppressed. [Means for solving the problem]

[0006] A semiconductor device according to an embodiment of the present disclosure includes a semiconductor substrate of a first conductivity type having a first main surface and a second main surface opposite to the first main surface, a first trench provided in the first main surface, a second trench provided in the first main surface, a first semiconductor layer of a second conductivity type provided on the first main surface between the first trench and the second trench, a second semiconductor layer of the first conductivity type provided at a position sandwiching the first trench between the first semiconductor layer of the first main surface and in contact with the first trench, a third semiconductor layer of the second conductivity type provided below the second semiconductor layer and in contact with the second semiconductor layer and the first trench, and a third semiconductor layer of the first conductivity type provided below the third semiconductor layer, in contact with the third semiconductor layer and separated from the first trench. a fourth semiconductor layer of a second conductivity type provided at a position sandwiching the second trench between the fourth semiconductor layer and the first semiconductor layer of the first main surface, a first insulating film provided on an inner wall of the first trench, a gate trench electrode provided in the first trench via the first insulating film and facing the third semiconductor layer, a second insulating film provided on an inner wall of the second trench, an emitter trench electrode provided in the second trench via the second insulating film, a gate electrode connected to the gate trench electrode, an emitter electrode connected to the emitter trench electrode, and a collector electrode provided on the second main surface, wherein a lower end of the fifth semiconductor layer is provided at a position equal to or lower than a lower end of the third semiconductor layer. Effect of the Invention

[0007] According to the present disclosure, the saturation voltage can be easily adjusted, and the variation in characteristics can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] 2 is a diagram showing a layout of a semiconductor layer and a trench electrode in the semiconductor device according to the first embodiment. FIG. [Diagram 2] 1 is a cross-sectional view showing a semiconductor device according to a first embodiment. [Diagram 3]1A to 1C are cross-sectional views (part 1) illustrating a method for manufacturing a semiconductor device according to a first embodiment. [Figure 4] 5A to 5C are cross-sectional views (part 2) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Diagram 5] 5A to 5C are cross-sectional views (part 3) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 6] 4A to 4C are cross-sectional views showing the method for manufacturing the semiconductor device according to the first embodiment; [Figure 7] 5A to 5C are cross-sectional views showing the method for manufacturing the semiconductor device according to the first embodiment; [Figure 8] 6 is a cross-sectional view (part 6) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 9] 7 is a cross-sectional view (part 7) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 10] 8 is a cross-sectional view showing the method for manufacturing the semiconductor device according to the first embodiment; FIG. [Figure 11] 9 is a cross-sectional view showing the method for manufacturing the semiconductor device according to the first embodiment; FIG. [Figure 12] 10 is a cross-sectional view showing the method for manufacturing the semiconductor device according to the first embodiment; FIG. [Figure 13] FIG. 4 is a cross-sectional view showing a semiconductor device according to a modified example of the first embodiment. [Figure 14] FIG. 13 is a graph showing Vce-Ic characteristics. [Figure 15] FIG. 13 is a diagram showing the results of a simulation regarding carrier concentration. [Figure 16] FIG. 4 is a cross-sectional view showing a semiconductor device according to a second embodiment. [Figure 17] FIG. 11 is a cross-sectional view showing a semiconductor device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations may be denoted by the same reference numerals to avoid repetitive description. In the following description, two directions parallel to the surface of the substrate and perpendicular to each other are defined as the X direction and the Y direction, and the direction perpendicular to the surface of the substrate is defined as the Z direction.

[0010] (First embodiment) First, a first embodiment will be described. The first embodiment relates to a semiconductor device including an insulated gate bipolar transistor (IGBT). FIG. 1 is a diagram showing a layout of a semiconductor layer and a trench electrode in the semiconductor device according to the first embodiment. FIG. 2 is a cross-sectional view showing the semiconductor device according to the first embodiment. FIG. 2 corresponds to a cross-sectional view taken along line II-II in FIG. 1.

[0011] As shown in FIG. 1, the semiconductor device 100 according to the first embodiment has an N-type semiconductor substrate 10 having a first main surface 10A and a second main surface 10B opposite to the first main surface 10A. The semiconductor substrate 10 is, for example, a silicon substrate. A plurality of gate trenches 21 and a plurality of emitter trenches 22 are formed on the first main surface 10A. The trenches 21 and 22 extend, for example, in the Y direction. For example, two trenches 21 form a pair, two trenches 22 form a pair, and the pairs of trenches 21 and the pairs of trenches 22 are alternately arranged in the X direction. The distance between two trenches 21 adjacent to each other in the X direction, the distance between two trenches 22 adjacent to each other in the X direction, and the distance between the trenches 21 and the trenches 22 adjacent to each other in the X direction are equal. That is, when the trenches 21 and the trenches 22 are not distinguished from each other, a plurality of trenches are formed in a stripe shape at equal intervals in the X direction on the first main surface 10A. A first region R1 is defined between two trenches 21 adjacent to each other in the X direction, a second region R2 is defined between the trenches 21 and the trenches 22 adjacent to each other in the X direction, and a third region R3 is defined between two trenches 22 adjacent to each other in the X direction. In the first embodiment, the first region R1 and the third region R3 are alternately arranged in the X direction as follows: ..., the third region R3, the second region R2, the first region R1, the second region R2, the third region R3, the second region R2, the first region R1, ..., and one second region R2 is arranged between the first region R1 and the third region R3.

[0012] In the first region R1, an N-type semiconductor layer 12 is provided on the first main surface 10A. The N-type semiconductor layer 12 contains N-type impurities at a higher concentration than the semiconductor substrate 10. The N-type semiconductor layer 12 is exposed to the first main surface 10A and is in contact with the trench 21. A P-type semiconductor layer 13 is provided under the N-type semiconductor layer 12. The P-type semiconductor layer 13 is in contact with the N-type semiconductor layer 12 and the trench 21. In the Z direction, the lower end of the P-type semiconductor layer 13 is above the lower end of the trench 21. A P-type semiconductor layer 17 is formed in the vicinity of the interface between the P-type semiconductor layer 13 and the N-type semiconductor layer 12. The P-type semiconductor layer 17 may be formed across the N-type semiconductor layer 12 and the P-type semiconductor layer 13, or may be formed to include the interface between the N-type semiconductor layer 12 and the P-type semiconductor layer 13. The P-type semiconductor layer 17 is separated from the trench 21. The P-type semiconductor layer 17 contains a P-type impurity at a higher concentration than the P-type semiconductor layer 13. In the Z direction, the lower end of the P-type semiconductor layer 17 is higher than the lower end of the P-type semiconductor layer 13. An N-type semiconductor layer 14 is provided below the P-type semiconductor layer 13. The N-type semiconductor layer 14 contains an N-type impurity at a higher concentration than the semiconductor substrate 10 and at a lower concentration than the N-type semiconductor layer 12. The N-type semiconductor layer 14 is in contact with the P-type semiconductor layer 13 and is separated from the trench 21.

[0013] In the second region R2, a P-type semiconductor layer 11 is provided on the first main surface 10A. The P-type semiconductor layer 11 is in contact with the trench 21 and the trench 22. For example, in the Z direction, the lower end of the P-type semiconductor layer 11 is higher than the lower end of the trench 21. For example, the depth of the P-type semiconductor layer 11 is equal to or greater than the depth of the trench 21. The P-type semiconductor layer 11 contains a lower concentration of P-type impurities than the P-type semiconductor layer 13.

[0014] In the third region R3, a P-type semiconductor layer 15 is provided on the first main surface 10A. For example, the P-type semiconductor layer 15 contains P-type impurities at a concentration similar to that of the P-type semiconductor layer 13. The P-type semiconductor layer 15 is exposed to the first main surface 10A and is in contact with the trench 22. For example, in the Z direction, the lower end of the P-type semiconductor layer 15 may be at the same position as the lower end of the P-type semiconductor layer 13, or may be lower than the lower end of the P-type semiconductor layer 13. For example, in the Z direction, the lower end of the P-type semiconductor layer 15 may be at the same position as the lower end of the P-type semiconductor layer 11, or may be higher than the lower end of the P-type semiconductor layer 11. The depth of the P-type semiconductor layer 15 may be equal to the depth of the P-type semiconductor layer 13, or may be greater than the depth of the P-type semiconductor layer 13 and equal to or less than the depth of the P-type semiconductor layer 11. A P-type semiconductor layer 18 is formed inside the P-type semiconductor layer 15. The P-type semiconductor layer 18 contains a P-type impurity at a higher concentration than the P-type semiconductor layer 15. For example, the P-type semiconductor layer 18 contains a P-type impurity at a concentration similar to that of the P-type semiconductor layer 17. An N-type semiconductor layer 16 is provided below the P-type semiconductor layer 15. The N-type semiconductor layer 16 contains an N-type impurity at a higher concentration than that of the semiconductor substrate 10. For example, the N-type semiconductor layer 16 contains an N-type impurity at a concentration similar to that of the N-type semiconductor layer 14. At least a portion of the N-type semiconductor layer 16 overlaps with the P-type semiconductor layer 15, contacts the P-type semiconductor layer 15, and is separated from the trench 22.

[0015] An insulating film 30 is provided on the inner walls of the trenches 21 and 22. An insulating film 31 is provided on the first main surface 10A. That is, the insulating film 31 covers the P-type semiconductor layer 11 and the N-type semiconductor layer 12. The insulating films 30 and 31 are, for example, thermal oxide films. A gate trench electrode 41 is provided in the trench 21 via the insulating film 30. The gate trench electrode 41 faces the P-type semiconductor layer 13 via the insulating film 30. An emitter trench electrode 42 is provided in the trench 22 via the insulating film 30. The gate trench electrode 41 and the emitter trench electrode 42 are formed using, for example, polycrystalline silicon. The insulating film 31 is also formed on the gate trench electrode 41 and the emitter trench electrode 42.

[0016] The portion of the insulating film 30 within the trench 21 functions as a gate insulating film. In the first region R1, the N-type semiconductor layer 12, the P-type semiconductor layer 13, and the N-type semiconductor substrate 10 are arranged along the insulating film 30 within the trench 21, and the P-type semiconductor layer 13 functions as a channel region. That is, the first region R1, the insulating film 30, and the gate trench electrode 41 form a MOS structure.

[0017] An interlayer insulating film 50 is provided on the insulating film 31. The interlayer insulating film 50 is, for example, a BPSG (borophosphosilicate glass) film. An opening 51 reaching the P-type semiconductor layer 17 is formed in the interlayer insulating film 50, the insulating film 31, and the N-type semiconductor layer 12. The opening 51 divides the N-type semiconductor layer 12 into two. An opening 52 reaching the P-type semiconductor layer 18 is formed in the interlayer insulating film 50, the insulating film 31, and the P-type semiconductor layer 15. An emitter electrode (emitter pad) 61 is provided on the interlayer insulating film 50. The emitter electrode 61 contacts the N-type semiconductor layer 12 and the P-type semiconductor layer 13 through the opening 51, and contacts the P-type semiconductor layers 15 and 18 through the opening 52. The emitter electrode 61 is formed of, for example, aluminum.

[0018] A P-type semiconductor layer 63 is provided on the second main surface 10B, and an N-type semiconductor layer 62 is provided above the P-type semiconductor layer 63. The N-type semiconductor layer 62 is in contact with the P-type semiconductor layer 63. The N-type semiconductor layer 62 contains N-type impurities at a higher concentration than the semiconductor substrate 10. A collector electrode 64 is provided on the second main surface 10B, i.e., below the P-type semiconductor layer 63. The collector electrode 64 is formed using a laminated film of Al, Ti, Ni, and Au laminated in order from the P-type semiconductor layer 63 downward. The collector electrode 64 may be formed using other materials, such as a laminated film of Al, Ti, Ni, and Ag laminated in order from the P-type semiconductor layer 63 downward.

[0019] Each gate trench electrode 41 is drawn out, for example, near the outer periphery of the semiconductor device 100 and commonly connected to a gate electrode (gate pad) (not shown). A shunt (resistor) may be provided between the gate trench electrode 41 and the gate electrode as appropriate so that the power supply delay time is uniform throughout the semiconductor device 100. The gate electrode is formed, for example, using aluminum. Each emitter trench electrode 42 is drawn out, for example, near the outer periphery of the semiconductor device 100 and connected to an emitter electrode (emitter pad) 61.

[0020] The P-type semiconductor layer 11 is not directly connected to the emitter electrode 61, the collector electrode 64, or the gate electrode, and is therefore electrically floating.

[0021] Although not shown, a so-called guard ring structure is provided on the outer periphery of the semiconductor device 100 to maintain a breakdown voltage.

[0022] Next, a method for manufacturing the semiconductor device 100 according to the first embodiment will be described. Figures 3 to 12 are cross-sectional views showing the method for manufacturing the semiconductor device 100 according to the first embodiment.

[0023] First, as shown in FIG. 3, a semiconductor substrate 10 having a first main surface 10A and a second main surface 10B is prepared, and a P-type semiconductor layer 11 is formed on the first main surface 10A in a region that becomes the second region R2 by ion implantation of P-type impurities and subsequent heat treatment.

[0024] 4, a plurality of gate trenches 21 and a plurality of emitter trenches 22 are formed on the first main surface 10A. In forming the trenches 21 and the trenches 22, for example, a photoresist mask is formed on the first main surface 10A, and the semiconductor substrate 10 is etched using this mask. A first region R1 is defined between two trenches 21 adjacent to each other in the X direction, a second region R2 is defined between the trenches 21 and 22 adjacent to each other in the X direction, and a third region R3 is defined between two trenches 22 adjacent to each other in the X direction.

[0025] 5, an insulating film 30 is formed on the inner walls of the trenches 21 and 22. The insulating film 30 is also formed on the first main surface 10A. The insulating film 30 can be formed by, for example, thermal oxidation.

[0026] Next, as shown in FIG. 6, a gate trench electrode 41 is formed in the trench 21 with the insulating film 30 interposed therebetween, and an emitter trench electrode 42 is formed in the trench 22 with the insulating film 30 interposed therebetween.

[0027] The P-type semiconductor layer 11 can be formed to a predetermined depth by heating during the formation of the insulating film 30 or the like.

[0028] Next, as shown in FIG. 7, the insulating film 30 is removed from the portion on the semiconductor substrate 10 and the portion on the P-type semiconductor layer 11. That is, the insulating film 30 is removed from the region in the first region R1 where the P-type semiconductor layer 13 and the N-type semiconductor layer 12 are formed, the region in the third region R3 where the P-type semiconductor layer 15 is formed, and the region in the second region R2 where the P-type semiconductor layer 11 is formed. Then, an insulating film 31 for ion implantation is formed in the region from which the insulating film 30 has been removed. The insulating film 31 for ion implantation is an insulating film thinner than the insulating film 30. The insulating film 31 can be formed by, for example, thermal oxidation. The insulating film 31 is also formed on the gate trench electrode 41 and the emitter trench electrode 42. Thereafter, the P-type semiconductor layer 13 is formed in the first region R1 by ion implantation of P-type impurities, and the P-type semiconductor layer 15 is formed in the third region R3. The P-type semiconductor layer 13 and the P-type semiconductor layer 15 can be formed simultaneously. The P-type semiconductor layer 13 and the P-type semiconductor layer 15 may be formed in different processes. Next, the N-type semiconductor layer 12 is formed in the first region R1 by ion implantation of N-type impurities. The insulating film 31 protects the surfaces of the semiconductor substrate 10 and the P-type semiconductor layer 11 during this ion implantation.

[0029] Next, as shown in FIG. 8, an interlayer insulating film 50 is formed on the insulating film 31.

[0030] 9, an opening 51 reaching the P-type semiconductor layer 13 is formed in the interlayer insulating film 50, the insulating film 31, and the N-type semiconductor layer 12, and an opening 52 reaching the P-type semiconductor layer 15 is formed in the interlayer insulating film 50 and the insulating film 31. The opening 51 and the opening 52 can be formed simultaneously. In forming the opening 51 and the opening 52, for example, a photoresist mask is formed on the interlayer insulating film 50, and the interlayer insulating film 50, the insulating film 31, the N-type semiconductor layer 12, and the P-type semiconductor layer 15 are etched using this mask. The opening 52 extends into the P-type semiconductor layer 15. The opening 51 may extend into the P-type semiconductor layer 13.

[0031] Next, as shown in FIG. 10, the N-type semiconductor layer 14 and the P-type semiconductor layer 17 in the first region R1, and the N-type semiconductor layer 16 and the P-type semiconductor layer 18 in the third region R3 are formed. In forming these semiconductor layers, ion implantation of N-type impurities for forming the N-type semiconductor layer 14 and the N-type semiconductor layer 16 is performed in the first region R1 and the third region R3, respectively. Next, ion implantation of P-type impurities for forming the P-type semiconductor layer 17 and the P-type semiconductor layer 18 is performed in the first region R1 and the third region R3, respectively. Then, after these ion implantations, a heat treatment is performed. In this manner, the N-type semiconductor layer 14, the N-type semiconductor layer 16, the P-type semiconductor layer 17, and the P-type semiconductor layer 18 can be formed. At least a portion of the N-type semiconductor layer 14 overlaps with the P-type semiconductor layer 13, and at least a portion of the N-type semiconductor layer 16 overlaps with the P-type semiconductor layer 15.

[0032] 11, an emitter electrode 61 is formed on the interlayer insulating film 50. The emitter electrode 61 contacts the N-type semiconductor layer 12 and the P-type semiconductor layer 13 through the opening 51, and contacts the P-type semiconductor layers 15 and 18 through the opening 52.

[0033] 12, an N-type semiconductor layer 62 is formed on the second main surface 10B by ion implantation of an N-type impurity. Furthermore, a P-type semiconductor layer 63 is formed on the second main surface 10B by ion implantation of a P-type impurity. Next, a collector electrode 64 is formed on the second main surface 10B.

[0034] Although not shown, gate electrodes connected to the respective gate trench electrodes 41 are formed.

[0035] For example, after the formation of the P-type semiconductor layer 17, the P-type semiconductor layer 18, the N-type semiconductor layer 14, and the N-type semiconductor layer 16, and before the formation of the emitter electrode 61, an opening (not shown) reaching the emitter trench electrode 42 may be formed in the interlayer insulating film 50 near the outer periphery of the semiconductor device 100. The emitter electrode 61 can be connected to the emitter trench electrode 42 through this opening.

[0036] Here, the effects of the semiconductor device 100 according to the first embodiment will be described.

[0037] In the semiconductor device 100 according to the first embodiment, the N-type semiconductor layer 14 functions as a hole barrier layer. In addition, the N-type semiconductor layer 14 is separated from the trench 21. Therefore, the characteristics of the MOS structure in the first region R1, such as the threshold voltage, are less likely to be affected by the N-type semiconductor layer 14. That is, according to the first embodiment, it is possible to suppress the variation in the characteristics of the MOS structure.

[0038] A second region R2 is provided adjacent to the first region R1, and a floating P-type semiconductor layer 11 is provided in the second region R2. Therefore, good static characteristics of the IGBT can be obtained due to the electron injection enhancement (IE) effect. In addition, the P-type semiconductor layer 11 and the P-type semiconductor layer 13 can be formed in separate processes, and for example, the P-type semiconductor layer 11 can be formed deeper than the P-type semiconductor layer 13. Therefore, it is possible to obtain excellent MOS characteristics in the first region R1 while obtaining excellent breakdown voltage.

[0039] A third region R3 is provided so as to sandwich the second region R2 between the first region R1 and the third region R3, and a trench 22 is provided between the second region R2 and the third region R3. If a gate trench electrode 41 is provided in the trench 22, the short circuit safe operation area (SCSOA) and switching characteristics may deteriorate due to an increase in gate capacitance. In the first embodiment, an emitter trench electrode 42 connected to an emitter electrode 61 is provided in the trench 22, so that deterioration of characteristics due to an increase in gate capacitance can be avoided.

[0040] When the trenches 21 and 22 are not differentiated from each other, a plurality of trenches are arranged in stripes at equal intervals in the X direction on the first main surface 10A. This results in high uniformity in the density of the trenches, and makes it possible to suppress processing variations in the etching process when forming the trenches. By suppressing processing variations, it is possible to improve the yield of the semiconductor device 100 and reduce variations in electrical characteristics.

[0041] In the third region R3, the P-type semiconductor layer 15 connected to the emitter electrode 61 is provided so as to be in contact with the N-type semiconductor substrate 10. This makes it possible to quickly discharge carriers during switching operation of the IGBT, thereby improving the switching characteristics.

[0042] Furthermore, the saturation voltage Vce(sat) can be adjusted depending on the depth of the P-type semiconductor layer 15. In the cross-sectional view shown in Fig. 2, the depth of the P-type semiconductor layer 15 is equal to the depth of the P-type semiconductor layer 13, but the depth of the P-type semiconductor layer 15 may be greater than the depth of the P-type semiconductor layer 13. Fig. 13 is a cross-sectional view showing a semiconductor device according to a modified example of the first embodiment.

[0043] In the semiconductor device 101 according to the modification of the first embodiment, the depth of the P-type semiconductor layer 15 is greater than the depth of the P-type semiconductor layer 13 and is equal to or less than the depth of the P-type semiconductor layer 11. The N-type semiconductor layer 16 is formed so as to entirely overlap the P-type semiconductor layer 15. The other configurations are similar to those of the first embodiment.

[0044] Comparing the semiconductor device 100 and the semiconductor device 101, the MOS characteristics are equivalent, and the saturation voltage Vce(sat) of the semiconductor device 100 is lower than the saturation voltage Vce(sat) of the semiconductor device 101. The inventors of the present application fabricated semiconductor devices according to the first embodiment and its modified examples, and the relationship between the collector-emitter voltage Vce and the collector current Ic (Vce-Ic characteristics) of each was actually measured, and the results are shown in FIG. 14. As shown in FIG. 14, the threshold voltage was equivalent between the first embodiment and its modified examples. On the other hand, the collector-emitter voltage Vce (saturation voltage Vce(sat)) when the rated collector current Ic was applied was smaller in the first embodiment than in the modified examples.

[0045] 15 shows the results of a simulation of carrier concentration performed by the inventors of the present application for the first embodiment and its modified example. In this simulation, the hole concentration distribution in the Z direction was calculated for a portion of the first region R1 including the N-type semiconductor layer 14 in a plan view and a portion of the third region R3 including the N-type semiconductor layer 16 in a plan view. The solid line in FIG. 15 shows the simulation result for the first region R1 of the first embodiment, the dashed line shows the simulation result for the third region R3 of the first embodiment, the one-dot chain line shows the simulation result for the first region R1 of the modified example, and the two-dot chain line shows the simulation result for the third region R3 of the modified example.

[0046] 15, a simulation result was obtained in which the hole concentration in both the first region R1 and the third region R3 in the first embodiment is higher than that in the modified example. This is considered to be because a kind of carrier accumulation effect is brought about in the first embodiment in which the P-type semiconductor layer 15 is formed shallower than in the modified example.

[0047] In this way, the saturation voltage Vce(sat) can be adjusted according to the depth of the P-type semiconductor layer 15, independently of the MOS characteristics. When the depth of the P-type semiconductor layer 15 is equal to the depth of the P-type semiconductor layer 13, the P-type semiconductor layer 15 and the P-type semiconductor layer 13 can be formed simultaneously. On the other hand, by forming the P-type semiconductor layer 15 and the P-type semiconductor layer 13 in separate steps, the saturation voltage Vce(sat) can be adjusted while obtaining desired MOS characteristics.

[0048] It is preferable that the N-type semiconductor layer 16 is spaced apart from the trench 22. This is because a better IE effect can be obtained and the saturation voltage Vce(sat) can be further reduced, thereby improving the efficiency of the semiconductor device 100.

[0049] The depth of the P-type semiconductor layer 11 is preferably equal to or greater than the depth of the trench 21. This is because electric field concentration at the bottom end of the trench 21 can be easily alleviated.

[0050] Second Embodiment Next, a second embodiment will be described. The second embodiment differs from the first embodiment mainly in the arrangement of the first region R1, the second region R2, and the third region R3. Figure 16 is a cross-sectional view showing the semiconductor device according to the second embodiment.

[0051] In the semiconductor device 200 according to the second embodiment, in addition to a plurality of gate trenches 21 and a plurality of emitter trenches 22, a plurality of emitter trenches 25 are formed on the first main surface 10A. The trenches 25 extend, for example, in the Y direction. As in the first embodiment, pairs of trenches 21 and pairs of trenches 22 are alternately arranged in the X direction. In addition, two trenches 25 are arranged between adjacent pairs of trenches 21 and pairs of trenches 22. The distance between two trenches 21 adjacent to each other in the X direction, the distance between two trenches 22 adjacent to each other in the X direction, the distance between two trenches 25 adjacent to each other in the X direction, the distance between the trenches 21 and the trench 25 adjacent to each other in the X direction, and the distance between the trenches 22 and the trench 25 adjacent to each other in the X direction are equal. That is, when the trenches 21, 22, and 25 are not differentiated from each other, a plurality of trenches are formed in the first main surface 10A in a stripe pattern at equal intervals in the X direction. As in the first embodiment, a first region R1 is defined between two trenches 21 adjacent to each other in the X direction, and a third region R3 is defined between two trenches 22 adjacent to each other in the X direction. A second region R2 is defined between the trenches 21 and 25 adjacent to each other in the X direction, between two trenches 25 adjacent to each other in the X direction, and between the trenches 25 and 22 adjacent to each other in the X direction. In the second embodiment, the first region R1 and the third region R3 are arranged alternately in the X direction as follows: ..., a third region R3, three second regions R2, a first region R1, three second regions R2, a third region R3, three second regions R2, a first region R1, ..., and three second regions R2 are arranged between the first region R1 and the third region R3.

[0052] In the second region R2, a P-type semiconductor layer 11 is provided on the first main surface 10A. The P-type semiconductor layer 11 contacts two trenches (trench 21, trench 22, or trench 25) that define the second region R2 in the X direction.

[0053] An insulating film 30 is also provided on the inner wall of the trench 25. An emitter trench electrode 45 is provided in the trench 25 with the insulating film 30 interposed therebetween. The emitter trench electrode 45 is formed using, for example, polycrystalline silicon. Like the emitter trench electrode 42, the emitter trench electrode 45 is extended to, for example, near the outer periphery of the semiconductor device 100 and connected to an emitter electrode (emitter pad) 61.

[0054] The other configuration is similar to that of the first embodiment.

[0055] The second embodiment also provides the same effects as the first embodiment, and further improves the IE effect and reduces the saturation voltage Vce(sat).

[0056] The number of trenches 25 disposed between adjacent pairs of trenches 21 and adjacent pairs of trenches 22 is not limited, and the number of trenches 25 may be one, or three or more.

[0057] (Third embodiment) Next, a third embodiment will be described. The third embodiment differs from the second embodiment mainly in the arrangement of the first region R1, the second region R2, and the third region R3. Fig. 17 is a cross-sectional view showing a semiconductor device according to the third embodiment.

[0058] In the semiconductor device 300 according to the third embodiment, in addition to a plurality of gate trenches 21, a plurality of emitter trenches 22, and a plurality of emitter trenches 25, a plurality of gate trenches 26 are formed on the first main surface 10A. The trenches 26 extend, for example, in the Y direction. As in the second embodiment, pairs of trenches 21 and pairs of trenches 22 are alternately arranged in the X direction. In addition, two trenches 25 are arranged between adjacent pairs of trenches 21 and pairs of trenches 22. Furthermore, one trench 26 is arranged between two adjacent trenches 25. The distance between two trenches 21 adjacent to each other in the X direction, the distance between two trenches 22 adjacent to each other in the X direction, the distance between the trenches 21 and 25 adjacent to each other in the X direction, the distance between the trenches 25 and 26 adjacent to each other in the X direction, and the distance between the trenches 22 and 25 adjacent to each other in the X direction are equal. That is, when the trenches 21, 22, 25, and 26 are not differentiated from each other, a plurality of trenches are formed in a stripe pattern at equal intervals in the X direction on the first main surface 10A. As in the second embodiment, a first region R1 is defined between two trenches 21 adjacent to each other in the X direction, and a third region R3 is defined between two trenches 22 adjacent to each other in the X direction. A second region R2 is defined between the trenches 21 and 25 adjacent to each other in the X direction, between the trenches 25 and 26 adjacent to each other in the X direction, and between the trenches 26 and 22 adjacent to each other in the X direction. In the third embodiment, the first regions R1 and the third regions R3 are arranged alternately in the X direction as follows: ..., a third region R3, four second regions R2, a first region R1, four second regions R2, a third region R3, four second regions R2, a first region R1, ..., and four second regions R2 are arranged between the first region R1 and the third region R3.

[0059] In the second region R2, a P-type semiconductor layer 11 is provided on the first main surface 10A. The P-type semiconductor layer 11 contacts two trenches (trench 21, trench 22, trench 25, or trench 26) that define the second region R2 in the X direction.

[0060] An insulating film 30 is also provided on the inner wall of the trench 26. A gate trench electrode 46 is provided in the trench 26 via the insulating film 30. The gate trench electrode 46 is formed using, for example, polycrystalline silicon. Like the gate trench electrode 41, the gate trench electrode 46 is extended to, for example, near the outer periphery of the semiconductor device 100 and connected to a gate electrode (gate pad) not shown.

[0061] The other configuration is similar to that of the second embodiment.

[0062] The third embodiment also provides the same effects as the second embodiment. In addition, the input capacitance can be increased while avoiding an increase in the gate capacitance in the MOS structure that affects the IGBT characteristics. This reduces gate noise.

[0063] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0064] 10: Semiconductor substrate 10A, 10B: Main surface 11, 13, 15, 17, 18, 63: P-type semiconductor layer 12, 14, 16, 62: N-type semiconductor layer 21, 22, 25, 26: Trench 30, 31: insulating film 41, 46: Gate trench electrode 42, 45: Emitter trench electrode 50: Interlayer insulating film 61: Emitter electrode 64: Collector electrode 100, 101, 200, 300: Semiconductor device R1, R2, R3: area

Claims

1. a semiconductor substrate of a first conductivity type having a first main surface and a second main surface opposite to the first main surface; a first trench provided in the first major surface; a second trench provided in the first major surface; a first semiconductor layer of a second conductivity type provided on the first major surface between the first trench and the second trench; a second semiconductor layer of a first conductivity type provided at a position sandwiching the first trench between the first semiconductor layer and the first main surface and in contact with the first trench; a third semiconductor layer of a second conductivity type provided under the second semiconductor layer and in contact with the second semiconductor layer and the first trench; a fourth semiconductor layer of the first conductivity type provided under the third semiconductor layer, in contact with the third semiconductor layer, and spaced apart from the first trench; a fifth semiconductor layer of a second conductivity type provided at a position sandwiching the second trench between the fifth semiconductor layer and the first main surface; a first insulating film provided on an inner wall of the first trench; a gate trench electrode provided in the first trench via the first insulating film and facing the third semiconductor layer; a second insulating film provided on an inner wall of the second trench; an emitter trench electrode provided in the second trench via the second insulating film; a gate electrode connected to the gate trench electrode; an emitter electrode connected to the emitter trench electrode; a collector electrode provided on the second main surface; having A semiconductor device, wherein a lower end of the fifth semiconductor layer is provided at a position equal to or lower than a lower end of the third semiconductor layer.

2. 2. The semiconductor device according to claim 1, wherein a lower end of said fifth semiconductor layer is provided at a position equal to or higher than a lower end of said first semiconductor layer.

3. 3 . The semiconductor device according to claim 1 , wherein a depth of said first semiconductor layer from said first main surface is equal to or greater than a depth of said first trench from said first main surface.

4. The semiconductor device according to claim 1 , wherein a position of a lower end of the fifth semiconductor layer coincides with a position of a lower end of the third semiconductor layer.

5. 5. The semiconductor device according to claim 4, wherein a lower end of said fifth semiconductor layer is provided at a position equal to or higher than a position of a lower end of said first semiconductor layer.

6. 6. The semiconductor device according to claim 1, further comprising a sixth semiconductor layer of the first conductivity type provided below the fifth semiconductor layer, in contact with the fifth semiconductor layer, and spaced apart from the second trench.

7. 7. The semiconductor device according to claim 1, wherein the emitter electrode is in contact with the second semiconductor layer, the third semiconductor layer, and the fifth semiconductor layer.

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