Semiconductor device

Abstract

This semiconductor device includes: a semiconductor region of a first conductivity type formed on a surface layer portion of a main surface of an SiC chip; an active region provided on the main surface; an outer peripheral region surrounding the periphery of the active region; a device structure that is formed in the active region and includes a body region of a second conductivity type formed in a surface layer portion of the semiconductor region and a source region of the first conductivity type formed on a surface layer portion of the body region; and an outer well region of the second conductivity type that is formed in the surface layer portion of the semiconductor region in the outer peripheral region and that includes a first outer well region formed along an outer peripheral boundary portion between the active region and the outer peripheral region, wherein the first outer well region includes a first region having a first impurity concentration and a second region that is formed closer to the main surface side than the first region and has a second impurity concentration higher than the first impurity concentration.

Description

Semiconductor Devices Related Applications

[0001] This application corresponds to Japanese Patent Application No. 2024-025723 filed with the Japan Patent Office on February 22, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to SiC semiconductor devices.

[0003] Patent Document 1 (US2008 / 0277669A1) discloses a semiconductor device having a termination structure in the peripheral region of a drift layer.

[0004] US Patent Application Publication No. 2008 / 0277669

[0005] [Summary] One embodiment of the present disclosure provides a semiconductor device including: a SiC chip having a main surface; a semiconductor region of a first conductivity type formed in a surface layer portion of the main surface; an active region provided on the main surface; a peripheral region provided on the main surface and surrounding a periphery of the active region; a device structure formed in the active region, the device structure including a body region of a second conductivity type formed in a surface layer portion of the semiconductor region and a source region of the first conductivity type formed in a surface layer portion of the body region; and an outer well region of the second conductivity type formed in a surface layer portion of the semiconductor region in the peripheral region, the outer well region including a first outer well region formed along a peripheral boundary between the active region and the peripheral region, the first outer well region including a first region having a first impurity concentration, and a second region formed closer to the main surface than the first region and having a second impurity concentration higher than the first impurity concentration.

[0006] FIG. 1 is a plan view showing a semiconductor device according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 . FIG. 3 is a plan view showing an example of a chip layout. FIG. 4 is a perspective view showing an example of a chip layout. FIG. 5 is an enlarged plan view showing a main portion of a first main surface shown in FIG. 3 . FIG. 6 is an enlarged plan view showing a main portion of a first main surface shown in FIG. 3 . FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 5 . FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 5 . FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 6 . FIG. 10 is a cross-sectional view showing a cross-sectional structure of the peripheral region taken along line XX in FIG. 1 . FIG. 11 is an enlarged cross-sectional view of a region shown in FIG. 10 . FIG. 12 is a plan view showing an example of a chip layout. FIG. 13A is a graph showing an example of a concentration gradient of p-type impurities in a region taken along line XIII-XIII in FIG. 9 . 13B is a graph showing an example of an n-type impurity concentration gradient in a region along line XIII-XIII shown in FIG. 9 . FIG. 14 is a graph showing an example of an n-type impurity concentration gradient in a region along line XIV-XIV shown in FIG. 9 . FIG. 15 is a graph showing an example of an n-type impurity concentration gradient in a region along line XV-XV shown in FIG. 10 . FIG. 16 is a graph showing an example of a p-type impurity concentration gradient in a region along line XVI-XVI shown in FIG. 11 . FIG. 17 is a cross-sectional view showing an outer well region according to a second embodiment. FIG. 18 is a cross-sectional view showing an outer well region according to a third embodiment. FIG. 19 is a cross-sectional view showing an outer well region according to a fourth embodiment. FIG. 20 is a cross-sectional view showing an outer well region according to a fifth embodiment. FIG. 21 is a graph showing a concentration gradient in an outer well region according to the second embodiment. FIG. 22 is a plan view showing an example of a chip layout of a semiconductor device according to a second embodiment of the present disclosure. FIG. 23 is an enlarged plan view showing a main portion of the first main surface shown in FIG. 22 . Fig. 24 is an enlarged plan view showing a main portion of the first main surface shown in Fig. 22. Fig. 25 is a cross-sectional view taken along line XXV-XXV shown in Fig. 23. Fig. 26 is a cross-sectional view taken along line XXVI-XXVI shown in Fig. 23. Fig. 27 is a cross-sectional view taken along line XXVII-XXVII shown in Fig. 24.

[0007] DETAILED DESCRIPTION Next, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0008] Specific embodiments will be described in detail below with reference to the accompanying drawings. The accompanying drawings are all schematic diagrams and are not strictly illustrative, and the relative positional relationships, scales, ratios, angles, etc. are not necessarily consistent. Corresponding structures among the accompanying drawings are given the same reference numerals, and duplicated descriptions are omitted or simplified. For structures whose descriptions are omitted or simplified, the descriptions given before the omission or simplification apply.

[0009] When the term "substantially" is used in this specification, this term includes a numerical value (form) equal to the numerical value (form) of the comparison target, as well as a numerical error (form error) within a range of ±10% based on the numerical value (form) of the comparison target. In the following description, terms such as "first," "second," and "third" are used, but these are symbols attached to the names of each structure to clarify the order of description, and are not intended to limit the names of each structure.

[0010] In the following description, the conductivity type of a semiconductor (impurity) is indicated using "p-type" or "n-type," but "p-type" may also be referred to as the "first conductivity type" and "n-type" as the "second conductivity type." "n-type" may also be referred to as the "first conductivity type" and "p-type" as the "second conductivity type." "p-type" is a conductivity type resulting from a trivalent element, and "n-type" is a conductivity type resulting from a pentavalent element. The trivalent element is at least one of boron, aluminum, gallium, and indium. The pentavalent element is at least one of nitrogen, phosphorus, arsenic, antimony, and bismuth.

[0011] Fig. 1 is a plan view showing a semiconductor device 1A according to a first embodiment of the present disclosure. Fig. 2 is a cross-sectional view taken along line II-II shown in Fig. 1. Fig. 3 is a plan view showing an example layout of a chip 2. Fig. 4 is a perspective view showing an example layout of the chip 2.

[0012] 1 to 4, a semiconductor device 1A is a semiconductor switching device having an insulated gate transistor structure Tr as an example of a device structure. The transistor structure Tr has a trench gate vertical structure.

[0013] Semiconductor device 1A includes chip 2 formed in a hexahedral shape (specifically, a rectangular parallelepiped shape). In this embodiment, chip 2 includes a single crystal of a wide bandgap semiconductor. In other words, semiconductor device 1A is a "wide bandgap semiconductor device." Chip 2 may also be referred to as a "semiconductor chip," a "wide bandgap semiconductor chip," or the like.

[0014] A wide bandgap semiconductor is a semiconductor having a bandgap that exceeds the bandgap of Si (silicon). Examples of wide bandgap semiconductors include GaN (gallium nitride), SiC (silicon carbide), and C (diamond). In this embodiment, the chip 2 is a "SiC chip" that includes a hexagonal SiC single crystal as an example of a wide bandgap semiconductor. In other words, the semiconductor device 1A is a "SiC semiconductor device."

[0015] Hexagonal SiC single crystal has a plurality of polytypes including 2H (Hexagonal)-SiC single crystal, 4H-SiC single crystal, 6H-SiC single crystal, etc. In this embodiment, an example is shown in which the chip 2 includes a 4H-SiC single crystal, but the chip 2 may also include other polytypes.

[0016] The chip 2 has a first main surface 3 on one side, a second main surface 4 on the other side, and first to fourth side surfaces 5A to 5D connected to the first main surface 3 and the second main surface 4. The first main surface 3 and the second main surface 4 are formed in a quadrangular shape in a plan view seen from the vertical direction Z (hereinafter simply referred to as "plan view"). The vertical direction Z is also the thickness direction of the chip 2.

[0017] The first main surface 3 and the second main surface 4 are preferably formed by the c-plane of the SiC single crystal. In this case, it is preferable that the first main surface 3 is formed by the silicon surface ((0001) surface) of the SiC single crystal, and the second main surface 4 is formed by the carbon surface ((000-1) surface) of the SiC single crystal.

[0018] The first side surface 5A and the second side surface 5B extend in a first direction X along the first main surface 3 and face a second direction Y that intersects with the first direction X along the first main surface 3. Specifically, the second direction Y is perpendicular to the first direction X. The third side surface 5C and the fourth side surface 5D extend in the second direction Y and face the first direction X.

[0019] In this embodiment, the first direction X is the m-axis direction ([1-100] direction) of the SiC single crystal, and the second direction Y is the a-axis direction ([11-20] direction) of the SiC single crystal. The first direction X may be the a-axis direction of the SiC single crystal, and the second direction Y may be the m-axis direction of the SiC single crystal. Hereinafter, the direction extending along the first main surface 3 may be referred to as the "horizontal direction." The horizontal direction is also the XY plane (horizontal plane) formed by the first direction X and the second direction Y, and is perpendicular to the vertical direction Z.

[0020] The chip 2 (first main surface 3 and second main surface 4) has an off-angle that is inclined at a predetermined angle in a predetermined off-direction with respect to the c-plane of the SiC single crystal. That is, the c-axis ((0001) axis) of the SiC single crystal is inclined by the off-angle from a vertical line along the vertical direction Z toward the off-direction. Furthermore, the c-plane of the SiC single crystal is inclined by the off-angle with respect to the horizontal plane.

[0021] The off-direction is preferably the a-axis direction of the SiC single crystal (second direction Y in this embodiment). The off-angle may be greater than 0° and less than or equal to 10°. The off-angle may have a value belonging to at least one of the ranges of greater than 0° and less than or equal to 1°, 1° to 2.5°, 2.5° to 5°, 5° to 7.5°, and 7.5° to 10°.

[0022] The off angle is preferably 5° or less. The off angle is particularly preferably 2° or more and 4.5° or less. The off angle is typically set in the range of 4°±0.1°. This specification does not exclude a configuration in which the off angle is 0° (i.e., a configuration in which the first main surface 3 is a just plane with respect to the c-plane).

[0023] The semiconductor device 1A includes an n-type first semiconductor region 6 formed in a surface layer portion of the second main surface 4. A drain potential as a first potential (high potential) is applied to the first semiconductor region 6. The first semiconductor region 6 may also be referred to as a "base region (layer)," a "semiconductor region (layer)," a "drain region (layer)," or the like.

[0024] The first semiconductor region 6 extends in a layered form along the second main surface 4 and is exposed from the second main surface 4 and the first to fourth side surfaces 5A to 5D. In this embodiment, the first semiconductor region 6 is made of an n-type semiconductor layer. Specifically, the first semiconductor region 6 is made of a substrate (SiC substrate) including a SiC single crystal (semiconductor single crystal), and forms the second main surface 4 and the first to fourth side surfaces 5A to 5D. The first semiconductor region 6 (substrate) has the off direction and off angle described above.

[0025] The first semiconductor region 6 may have a thickness T1 of 10 μm to 500 μm inclusive. The thickness T1 of the first semiconductor region 6 may have a value belonging to at least one of the ranges of 10 μm to 50 μm inclusive, 50 μm to 100 μm inclusive, 100 μm to 150 μm inclusive, 150 μm to 200 μm inclusive, 200 μm to 300 μm inclusive, 300 μm to 400 μm inclusive, and 400 μm to 500 μm inclusive.

[0026] The semiconductor device 1A includes an n-type second semiconductor region 7 formed in a surface layer portion of the first main surface 3. The second semiconductor region 7 may also be referred to as a "semiconductor region (layer)," a "drift region (layer)," or the like. The second semiconductor region 7 has an n-type impurity concentration lower than the n-type impurity concentration of the first semiconductor region 6. The second semiconductor region 7 is formed in a region closer to the first main surface 3 than the first semiconductor region 6 in a cross-sectional view, and is electrically connected to the first semiconductor region 6.

[0027] The second semiconductor region 7 extends in a layered form along the first main surface 3 and is exposed from the first main surface 3 and the first to fourth side surfaces 5A to 5D. In this embodiment, the second semiconductor region 7 is made of an n-type semiconductor layer. Specifically, the second semiconductor region 7 is made of an epitaxial layer (SiC epitaxial layer) including a SiC single crystal (semiconductor single crystal), and forms the first main surface 3 and the first to fourth side surfaces 5A to 5D.

[0028] The second semiconductor region 7 (epitaxial layer) has the aforementioned off direction and off angle. The second semiconductor region 7 preferably has a thickness T2 that is less than the thickness T1 of the first semiconductor region 6. The thickness T2 of the second semiconductor region 7 may be greater than the thickness T1 of the first semiconductor region 6.

[0029] The thickness T2 of the second semiconductor region 7 may be 5 μm or more and 15 μm or less. The thickness T2 of the second semiconductor region 7 may have a value belonging to at least one of the ranges of 5 μm or more and 7.5 μm or less, 7.5 μm or more and 10 μm or less, 10 μm or more and 12.5 μm or less, and 12.5 μm or more and 15 μm or less.

[0030] The semiconductor device 1A includes an active region 8 set in a chip 2. The active region 8 includes a device structure (transistor structure Tr) and is a region where an output current (drain current) is generated. The active region 8 is set in an inner portion of the chip 2 at a distance from the periphery of the first main surface 3 (first to fourth side surfaces 5A to 5D).

[0031] The active region 8 is set to a polygonal shape (a quadrilateral shape in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view. The ratio (area ratio) of the planar area of ​​the active region 8 to the planar area of ​​the first main surface 3 may be 0.5 or more and 0.95 or less. The area ratio may be 0.5 or more and 0.6 or less, 0.6 or more and 0.7 or less, 0.7 or more and 0.8 or less, 0.8 or more and 0.9 or less, or 0.9 or more and 0.95 or less.

[0032] The semiconductor device 1A includes a peripheral region 9 set outside the active region 8 in the chip 2. The peripheral region 9 is a region that does not include a device structure (transistor structure Tr). The peripheral region 9 is set on the periphery of the chip 2. That is, the peripheral region 9 is provided in the region between the periphery of the chip 2 and the active region 8 in plan view. The peripheral region 9 extends in a strip shape along the active region 8 in plan view and is set in the shape of a polygonal ring (a square ring in this embodiment) that surrounds the active region 8.

[0033] The semiconductor device 1A includes a plurality of trench-type (trench electrode-type) gate structures 15 formed in the active region 8. The gate structures 15 may also be referred to as "trench structures," "trench gate structures," or the like.

[0034] The plurality of gate structures 15 are formed in an inner portion of the first main surface 3 at intervals from the periphery (first to fourth side surfaces 5A to 5D) of the first main surface 3, and are not formed in the outer peripheral region 9. The plurality of gate structures 15 are arranged at intervals in a first direction X (= m-axis direction) in a plan view, and each extends in a band shape in a second direction Y (= a-axis direction). The plurality of gate structures 15 are arranged in a stripe shape extending in the second direction Y in a plan view.

[0035] The semiconductor device 1A includes a p-type outer well region 40 formed in the peripheral region 9. The outer well region 40 includes a first outer well region 42 and a plurality of second outer well regions 43.

[0036] 3 and 4 , the first outer well region 42 is a quadrangular ring-shaped region defined by a thick solid line and a thick dashed line. The first outer well region 42 has a portion extending in a first direction X and a portion extending in a second direction Y. In this embodiment, the first outer well region 42 is formed in a polygonal ring shape (a quadrangular ring in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view, and surrounds a plurality of gate structures 15.

[0037] The first outer well region 42 may have an edge portion that connects the portion extending in the first direction X and the portion extending in the second direction Y in an arc shape (preferably a quadrant arc shape). In this embodiment, the first outer well region 42 is formed in the peripheral region 9 and surrounds the active region 8.

[0038] 3 and 4 , each of the multiple second outer well regions 43 has a portion extending in the first direction X and a portion extending in the second direction Y. In this embodiment, each second outer well region 43 is formed in a polygonal ring shape (a square ring in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view, and surrounds the first outer well region 42.

[0039] Each of the plurality of second outer well regions 43 may have an edge portion that connects the portion extending in the first direction X and the portion extending in the second direction Y in an arc shape (preferably a quarter arc shape). In this embodiment, the plurality of second outer well regions 43 are arranged in the outer periphery region 9 at intervals outward from the first outer well region 42.

[0040] The semiconductor device 1A includes an insulating interlayer film 47 formed on the first main surface 3. The interlayer film 47 may be referred to as an "insulating film," an "interlayer insulating film," an "intermediate insulating film," or the like. The interlayer film 47 may include at least one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. The interlayer film 47 preferably includes a silicon oxide film.

[0041] The semiconductor device 1A includes a source electrode 51 disposed on the first main surface 3. The source electrode 51 is a terminal electrode to which a source potential is applied from the outside. The source electrode 51 may also be referred to as a "source pad electrode," a "first pad electrode," a "first main surface electrode," a "first terminal electrode," or the like. The source electrode 51 is disposed on a portion of the interlayer film 47 that covers the active region 8.

[0042] In this embodiment, the source electrode 51 has a first pad portion 51 a, a second pad portion 51 b, and a third pad portion 51 c. The first pad portion 51 a has a relatively large planar area and forms the main body of the source electrode 51. In this embodiment, the first pad portion 51 a is formed in a polygonal shape (a quadrangle in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view, and is located closer to the fourth side surface 5D than the center of the first main surface 3.

[0043] The second pad portion 51b has a planar area smaller than that of the first pad portion 51a, and extends in a strip shape (rectangular) from one end of the first pad portion 51a in the second direction Y (the end on the first side surface 5A side) toward the third side surface 5C. The third pad portion 51c has a planar area smaller than that of the first pad portion 51a, and extends in a strip shape (rectangular) from the other end of the first pad portion 51a in the second direction Y (the end on the second side surface 5B side) toward the third side surface 5C, and faces the second pad portion 51b in the second direction Y.

[0044] The plane area of ​​the third pad portion 51c may be approximately equal to the plane area of ​​the second pad portion 51b. The plane area of ​​the third pad portion 51c may be larger than the plane area of ​​the second pad portion 51b, or may be smaller than the plane area of ​​the second pad portion 51b. Either or both of the second pad portion 51b and the third pad portion 51c may be used as a terminal portion for monitoring current.

[0045] The source electrode 51 does not necessarily have to have both the second pad portion 51 b and the third pad portion 51 c at the same time. The source electrode 51 may have only one of the second pad portion 51 b and the third pad portion 51 c. The source electrode 51 may be composed of only the first pad portion 51 a, and may not have both the second pad portion 51 b and the third pad portion 51 c.

[0046] The semiconductor device 1A includes a source wiring 56 arranged around the source electrode 51 on the interlayer film 47. The same potential (source potential) as the potential (source potential) applied to the source electrode 51 is applied to the source wiring 56. The source wiring 56 may also be referred to as a "termination electrode (wiring)," "wiring," "first wiring," "finger electrode," "source finger," or the like.

[0047] The source wiring 56 has a wiring width less than the electrode width of the source electrode 51, and is selectively routed on the interlayer film 47. In this embodiment, the source wiring 56 is drawn from the source electrode 51 (first pad portion 51 a) to the fourth side surface 5D. The source wiring 56 is drawn from the active region 8 to the peripheral region 9.

[0048] The source wiring 56 extends in a strip shape along the periphery of the first main surface 3 (the periphery of the active region 8). In this embodiment, the source wiring 56 is formed in a polygonal ring shape (a square ring shape in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view, and surrounds the inner part of the first main surface 3 (the active region 8). The source wiring 56 may have an edge portion that connects the portion extending in the first direction X and the portion extending in the second direction Y in an arc shape (preferably a quadrant arc shape). The source wiring 56 may be either ended or endless.

[0049] The semiconductor device 1A includes a gate electrode 57 disposed on the first main surface 3. The gate electrode 57 is a terminal electrode to which a gate potential is applied from the outside. The gate electrode 57 may also be referred to as a "second pad electrode," a "second main surface electrode," a "second terminal electrode," or the like.

[0050] The gate electrode 57 is disposed on a portion of the interlayer film 47 that covers the active region 8, with a gap between it and the source electrode 51. In this embodiment, the gate electrode 57 is disposed in a region on the third side surface 5C side of the first pad portion 51a, and faces the first pad portion 51a in the first direction X. The gate electrode 57 is interposed in a region between the second pad portion 51b and the third pad portion 51c, and faces both the second pad portion 51b and the third pad portion 51c in the second direction Y.

[0051] The gate electrode 57 is formed in a polygonal shape (a quadrilateral shape in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view. The gate electrode 57 has a planar area less than the planar area of ​​the source electrode 51. The gate electrode 57 has a planar area less than the planar area of ​​the first pad portion 51a. The gate electrode 57 may also have a planar area less than the planar area of ​​the second pad portion 51b (third pad portion 51c).

[0052] The semiconductor device 1A includes a gate wiring 58 extending from the gate electrode 57 onto the first main surface 3. The gate wiring 58 may also be referred to as a "wiring," a "second wiring," a "finger electrode," a "gate finger," or the like. The gate wiring 58 transmits the gate potential applied to the gate electrode 57 to other regions.

[0053] The gate wiring 58 is drawn out from the gate electrode 57 onto the portion of the interlayer film 47 that covers the active region 8, and is routed to the region between the source electrode 51 and the source wiring 56 at a distance from the source electrode 51 and the source wiring 56.

[0054] The gate wiring 58 has a portion extending in a strip shape in the first direction X in a plan view and a portion extending in a strip shape in the second direction Y, and intersects (specifically, orthogonally) with ends (both ends in this embodiment) of the plurality of gate structures 15. In this embodiment, the gate wiring 58 is formed in a strip shape with ends having four sides parallel to the periphery of the first main surface 3, and surrounds the source electrode 51.

[0055] The semiconductor device 1A includes a drain electrode 59 covering the second main surface 4. The drain electrode 59 is a terminal electrode to which a drain potential is applied from the outside. The drain electrode 59 may also be referred to as a "third pad electrode," a "third main surface electrode," a "third terminal electrode," or the like.

[0056] The drain electrode 59 is electrically connected to the first semiconductor region 6. The drain electrode 59 may cover the entire second main surface 4 so as to be continuous with the periphery (first to fourth side surfaces 5A to 5D) of the second main surface 4. The drain electrode 59 may also cover a portion of the second main surface 4 so as to expose the periphery of the second main surface 4.

[0057] A breakdown voltage that can be applied between source electrode 51 and drain electrode 59 (between first main surface 3 and second main surface 4) may be 500 V or more and 3000 V or less. The breakdown voltage may have a value belonging to at least one of the ranges of 500 V or more and 750 V or less, 750 V or more and 1000 V or less, 1000 V or more and 1250 V or less, 1250 V or more and 1500 V or less, 1500 V or more and 1750 V or less, 1750 V or more and 2000 V or less, 2000 V or more and 2250 V or less, 2250 V or more and 2500 V or less, 2500 V or more and 2750 V or less, and 2750 V or more and 3000 V or less.

[0058] FIG. 5 is an enlarged plan view showing a main portion of the first main surface 3 shown in FIG. 3. FIG. 6 is an enlarged plan view showing a main portion of the first main surface 3 shown in FIG. 3. FIG. 7 is a cross-sectional view taken along line VII-VII shown in FIG. 5. FIG. 8 is a cross-sectional view taken along line VIII-VIII shown in FIG. 5. FIG. 9 is a cross-sectional view taken along line IX-IX shown in FIG. 6. FIG. 10 is a cross-sectional view showing the cross-sectional structure of the outer peripheral region 9 taken along line XX shown in FIG. 1. FIG. 11 is an enlarged cross-sectional view of one region shown in FIG. 10. FIG. 12 is a plan view showing an example layout of the chip 2. FIGS. 9 to 12 show an outer well region 40 according to a first embodiment of the semiconductor device 1A.

[0059] The transistor structure Tr formed in the active region 8 of the semiconductor device 1A and the configuration within the peripheral region 9 will be described with reference to FIGS.

[0060] The semiconductor device 1A includes a p-type body region 10 formed in the active region 8 (inner portion of the first main surface 3) in a surface layer portion of the first main surface 3. The body region 10 may also be referred to as an "impurity region," a "channel region," or the like. A source potential may be applied to the body region 10. The source potential may be a reference potential that serves as a reference for circuit operation. The reference potential may be a ground potential. The body region 10 has a p-type impurity concentration that is higher than the n-type impurity concentration of the second semiconductor region 7. The body region 10 has a p-type impurity concentration of, for example, 1×10 １７ cm －３ 1x10 or more １８ cm －３ The p-type impurity concentration may have the following peak value:

[0061] 10 , the body region 10 is formed in the inner portion of the first main surface 3 at a distance from the periphery (first to fourth side surfaces 5A to 5D) of the first main surface 3, and is not formed in the outer peripheral region 9. In this embodiment, the body region 10 is formed throughout the active region 8. The body region 10 is formed in the surface layer portion of the second semiconductor region 7, and extends in a layered form along the first main surface 3.

[0062] The body region 10 is formed at a distance from the bottom of the second semiconductor region 7 (first semiconductor region 6) toward the first main surface 3, and faces the first semiconductor region 6 across a part of the second semiconductor region 7. The body region 10 is formed at a distance from a depth position of the middle part of the second semiconductor region 7 toward the first main surface 3.

[0063] The body region 10 is formed in a region on the first main surface 3 side of the second semiconductor region 7 in a cross-sectional view, and is electrically connected to the second semiconductor region 7. The body region 10 forms a pn junction (body diode) with the second semiconductor region 7. The body region 10 spreads a depletion layer into the second semiconductor region 7 when a reverse bias voltage is applied. The depletion layer originating in the body region 10 spreads in the horizontal direction and thickness direction within the second semiconductor region 7.

[0064] The semiconductor device 1A includes an n-type source region 11 formed in the active region 8 in a surface layer portion of the first main surface 3. A source potential is applied to the source region 11. The source region 11 has an n-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The n-type impurity concentration of the source region 11 is higher than the p-type impurity concentration of the body region 10.

[0065] The source region 11 is formed in an inner portion of the first main surface 3 at a distance from the periphery (first to fourth side surfaces 5A to 5D) of the first main surface 3, and is not formed in the outer peripheral region 9. The source region 11 may be formed inwardly at a distance from the periphery of the body region 10. The source region 11 is formed in a surface layer portion of the body region 10, and extends in a layered form along the first main surface 3.

[0066] The source region 11 is formed at a distance from the bottom of the body region 10 toward the first main surface 3, and faces the second semiconductor region 7 across a part of the body region 10. The source region 11 is formed in a region on the first main surface 3 side of the body region 10 in a cross-sectional view, and is electrically connected to the body region 10.

[0067] The semiconductor device 1A includes a plurality of trench-type (trench electrode-type) gate structures 15 formed in an inner portion of the first main surface 3. The gate structures 15 may also be referred to as "trench structures," "trench gate structures," or the like. A gate potential (gate signal) serving as a control potential is applied to the plurality of gate structures 15. The plurality of gate structures 15 controls inversion and non-inversion of the channel in the body region 10 in response to the gate potential.

[0068] The plurality of gate structures 15 are formed in an inner portion of the first main surface 3 at intervals from the periphery (first to fourth side surfaces 5A to 5D) of the first main surface 3, and are not formed in the outer peripheral region 9. The plurality of gate structures 15 are arranged at intervals in a first direction X (= m-axis direction) in a plan view, and each extends in a band shape in a second direction Y (= a-axis direction). The plurality of gate structures 15 are arranged in a stripe shape extending in the second direction Y in a plan view.

[0069] The extension direction of the multiple gate structures 15 coincides with the off-direction of the SiC single crystal. With respect to the second direction Y, both ends of the multiple gate structures 15 may be located in a region between the peripheral edge of the body region 10 and the peripheral edge of the source region 11. The multiple gate structures 15 may be arranged at intervals in the second direction Y in a plan view, and each extend in a strip shape in the first direction X.

[0070] The plurality of gate structures 15 penetrates the body region 10 and the source region 11 to reach the second semiconductor region 7. The plurality of gate structures 15 are formed at intervals from the depth position of the bottom of the second semiconductor region 7 toward the first main surface 3, and face the first semiconductor region 6 with a part of the second semiconductor region 7 in between.

[0071] The plurality of gate structures 15 may be formed at intervals from a depth position of an intermediate portion of the second semiconductor region 7 toward the first main surface 3, or may be located on the bottom side of the second semiconductor region 7 with respect to the depth position of the intermediate portion of the second semiconductor region 7. The plurality of gate structures 15 are formed substantially perpendicular to the first main surface 3. The plurality of gate structures 15 may be formed in a shape that tapers toward the bottom of the second semiconductor region 7.

[0072] The side walls (long sides) of the plurality of gate structures 15 are formed by the m-plane ((1-100) plane) of the SiC single crystal. The side walls (long sides) of the plurality of gate structures 15 may be formed by the a-plane ((11-20) plane) of the SiC single crystal depending on the extension direction of the gate structures 15. The bottom walls of the plurality of gate structures 15 are formed by the c-plane (Si-plane) of the SiC single crystal. It is preferable that the bottom walls of the plurality of gate structures 15 extend substantially flat in the horizontal direction. The bottom walls of the plurality of gate structures 15 may be curved in an arc shape toward the second main surface 4.

[0073] The inclination angle (absolute value) of the sidewall (long side) of the gate structure 15 relative to the vertical line may be 85° or more and 95° or less. The inclination angle may have a value belonging to at least one of the ranges of 85° or more and 87.5° or less, 87.5° or more and 90° or less, 90° or more and 92.5° or less, and 92.5° or more and 95° or less. The inclination angle is preferably 87° or more and 93° or less.

[0074] The gate structure 15 may have a width of 0.1 μm to 2 μm, and may have a width in at least one of the ranges of 0.1 μm to 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 0.75 μm, 0.75 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, and 1.75 μm to 2 μm.

[0075] The gate structure 15 may have a depth of 0.1 μm or more and 3 μm or less. The depth of the gate structure 15 is measured from the first main surface 3. The depth of the gate structure 15 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.5 μm or less, 0.5 μm or more and 1 μm or less, 1 μm or more and 1.5 μm or less, 1.5 μm or more and 2 μm or less, 2 μm or more and 2.5 μm or less, and 2.5 μm or more and 3 μm or less. The depth of the gate structure 15 is preferably 0.5 μm or more and 1.5 μm or less.

[0076] The gate structure 15 may have an aspect ratio of 1 to 3. The aspect ratio of the gate structure 15 is the ratio of the depth of the gate structure 15 to the width of the gate structure 15. The aspect ratio may have a value belonging to at least one of the ranges of 1 to 1.25, 1.25 to 1.5, 1.5 to 1.75, 1.75 to 2, 2 to 2.25, 2.25 to 2.5, 2.5 to 2.75, and 2.75 to 3. The aspect ratio is preferably 1.5 to 2.5.

[0077] Each of the plurality of gate structures 15 includes a first trench 16, a first insulating film 17, and a first buried electrode 18. The first trench 16 is formed in the first main surface 3 and defines the wall surfaces (sidewalls and bottom wall) of the gate structure 15.

[0078] The first insulating film 17 may include at least one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. In this embodiment, the first insulating film 17 has a single-layer structure made of a silicon oxide film. It is particularly preferable that the first insulating film 17 includes a silicon oxide film made of an oxide of the chip 2.

[0079] The first insulating film 17 covers the wall surface of the first trench 16. The first insulating film 17 includes a first film portion and a second film portion. The first film portion covers the sidewall of the first trench 16 in a film-like manner. The second film portion covers the bottom wall of the first trench 16 in a film-like manner and is continuous with the first film portion. The second film portion has a thickness greater than that of the first film portion. The thickness of the second film portion may be approximately equal to the thickness of the first film portion.

[0080] The first insulating film 17 may have a thickness of 10 nm to 150 nm, and may have a thickness in at least one range of 10 nm to 25 nm, 25 nm to 50 nm, 50 nm to 75 nm, 75 nm to 100 nm, 100 nm to 125 nm, and 125 nm to 150 nm.

[0081] The first buried electrode 18 is buried in the first trench 16 with the first insulating film 17 sandwiched therebetween. The first buried electrode 18 may include either p-type conductive polysilicon or n-type conductive polysilicon, or both. The first buried electrode 18 faces the second semiconductor region 7, the body region 10, and the source region 11 with the first insulating film 17 sandwiched therebetween.

[0082] The first buried electrode 18 has an electrode surface exposed from the first trench 16. The electrode surface is located closer to the bottom wall of the first trench 16 with respect to the height position of the first main surface 3. The electrode surface is located closer to the first main surface 3 with respect to the depth position of the bottom of the source region 11. The electrode surface has a recess in an inner portion that tapers toward the bottom wall of the first trench 16.

[0083] The semiconductor device 1A includes gate well regions 25 formed in the chip 2 (second semiconductor region 7) in the active region 8 in regions below the plurality of gate structures 15. The gate well regions 25 may also be referred to as "first well regions" or the like.

[0084] A source potential is applied to the gate well region 25. The gate well region 25 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the gate well region 25 may be higher than the p-type impurity concentration of the body region 10, or may be lower than the p-type impurity concentration of the body region 10. The p-type impurity (trivalent element) of the gate well region 25 is preferably aluminum.

[0085] The multiple gate well regions 25 are formed in the second semiconductor region 7 in regions below (specifically, directly below) the multiple gate structures 15, spaced apart from one another in the horizontal direction (first direction X). The multiple gate well regions 25 are formed in the thickness range between the bottom of the second semiconductor region 7 and the bottom walls of the multiple gate structures 15, and overlap the multiple gate structures 15 in a one-to-one correspondence in the thickness direction.

[0086] The multiple gate well regions 25 each extend in a strip shape in the second direction Y in plan view, following the extension direction of the corresponding gate structure 15. In other words, the multiple gate well regions 25 are arranged in stripes extending in the second direction Y in plan view.

[0087] The extension direction of the multiple gate well regions 25 coincides with the off-direction of the SiC single crystal. The multiple gate well regions 25 may extend in the first direction X according to the extension direction of the multiple gate structures 15. In this case, the multiple gate well regions 25 intersect (specifically, are perpendicular to) the off-direction.

[0088] The plurality of gate well regions 25 are formed at intervals from the bottom of the second semiconductor region 7 toward the bottom wall sides of the plurality of gate structures 15, and face the first semiconductor region 6 across a part of the second semiconductor region 7. The plurality of gate well regions 25 each have an upper end located on the bottom wall side of the corresponding gate structure 15, and a bottom located on the bottom side of the second semiconductor region 7 (the side of the second main surface 4).

[0089] The upper ends of the plurality of gate well regions 25 are formed at intervals from the bottom of the body region 10 toward the bottom wall of the corresponding gate structure 15. The upper ends of the plurality of gate well regions 25 may be connected to the bottom wall of the corresponding gate structure 15. The upper ends of the plurality of gate well regions 25 may have portions that extend along the sidewall of the corresponding gate structure 15. The upper ends of the plurality of gate well regions 25 may be formed at intervals from the bottom wall of the corresponding gate structure 15 toward the bottom of the second semiconductor region 7.

[0090] The bottoms of the multiple gate well regions 25 may be located on the bottom wall side of the multiple gate structures 15 relative to the intermediate portion of the second semiconductor region 7, or may be located on the bottom side of the second semiconductor region 7 (the side toward the second main surface 4) relative to the intermediate portion of the second semiconductor region 7.

[0091] Each of the plurality of gate well regions 25 has a bulging portion 25 a. The bulging portion 25 a extends in an arc shape in the horizontal direction from a region directly below the corresponding gate structure 15 to both sides of the corresponding gate structure 15. Each of the plurality of gate well regions 25 is formed in a tapered shape from the bulging portion 25 a to the bottom.

[0092] The gate well region 25 may have a width greater than or less than the width of the gate structure 15. The width of the gate well region 25 may be 0.1 μm or more and 2 μm or less. The width of the gate well region 25 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.25 μm or less, 0.25 μm or more and 0.5 μm or less, 0.5 μm or more and 0.75 μm or less, 0.75 μm or more and 1 μm or less, 1 μm or more and 1.25 μm or less, 1.25 μm or more and 1.5 μm or less, 1.5 μm or more and 1.75 μm or less, and 1.75 μm or more and 2 μm or less.

[0093] The gate well region 25 may have a depth less than the depth of the gate structure 15, or may have a depth greater than the depth of the gate structure 15. The depth of the gate well region 25 is the depth of the gate well region 25 when the bottom wall of the gate structure 15 is used as the reference.

[0094] The depth of the gate well region 25 may be greater than 0 μm and less than or equal to 5 μm. The depth of the gate well region 25 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than or equal to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, 3.5 μm to 4 μm, 4 μm to 4.5 μm, and 4.5 μm to 5 μm.

[0095] The gate well region 25 may have an aspect ratio greater than 0 and less than or equal to 2. The aspect ratio of the gate well region 25 is the ratio of the depth of the gate well region 25 to the width of the gate well region 25.

[0096] The aspect ratio may have a value belonging to at least one of the ranges of greater than 0 and less than or equal to 0.25, 0.25 or more and less than or equal to 0.5, 0.5 or more and less than or equal to 0.75, 0.75 or more and less than or equal to 1, 1 or more and less than or equal to 1.25, 1.25 or more and less than or equal to 1.5, 1.5 or more and less than or equal to 1.75, and 1.75 or more and less than or equal to 2.

[0097] The gate well region 25 forms a pn junction with the second semiconductor region 7. When a reverse bias voltage is applied, the gate well region 25 spreads a depletion layer into the second semiconductor region 7. The depletion layer originating from the gate well region 25 spreads in the horizontal and thickness directions, and reduces the electric field applied to the active region 8 (gate structure 15).

[0098] 5, 6, and 8, the semiconductor device 1A includes a plurality of gate contact regions 27 formed in the chip 2 (second semiconductor region 7) in the active region 8. The gate contact regions 27 may also be referred to as "first contact regions," etc. A source potential is applied to the gate contact regions 27.

[0099] The gate contact region 27 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the gate contact region 27 is higher than the p-type impurity concentration of the body region 10. The p-type impurity concentration of the gate contact region 27 is higher than the p-type impurity concentration of the gate well region 25.

[0100] The plurality of gate contact regions 27 are formed at intervals in regions along the plurality of gate structures 15. The plurality of gate contact regions 27 are formed in a one-to-many correspondence with the plurality of gate structures 15. The plurality of gate contact regions 27 are formed at intervals in the second direction Y following the extension direction of the corresponding gate structures 15.

[0101] With respect to one and the other gate structures 15, the multiple gate contact regions 27 along one gate structure 15 face the multiple gate contact regions 27 along the other gate structure 15 in the first direction X in plan view. In other words, the multiple gate contact regions 27 are generally arranged in a matrix with gaps in the first direction X and the second direction Y in plan view.

[0102] In plan view, one of the plurality of gate contact regions 27 may face, in the first direction X, a region between the other of the plurality of gate contact regions 27. In other words, the plurality of gate contact regions 27 may be generally arranged in a staggered pattern at intervals in the first direction X and the second direction Y in plan view.

[0103] In this embodiment, the gate contact regions 27 extend in a strip shape along the gate structures 15 in a plan view. The lengths of the gate contact regions 27 in the second direction Y may be equal to or different from one another. The lengths of the gate contact regions 27 in the second direction Y are adjusted depending on the channel area to be formed.

[0104] The channel area is the total area of ​​the portions of the source region 11 exposed from the plurality of gate contact regions 27. That is, the channel area increases or decreases depending on the ratio of the total planar area of ​​the plurality of gate contact regions 27. The total planar area of ​​the plurality of gate contact regions 27 is preferably less than the channel area.

[0105] That is, in the region between a pair of adjacent gate structures 15, the total planar area of ​​the multiple gate contact regions 27 is preferably less than the planar area of ​​the source region 11. With this configuration, an increase in the resistance value (on-resistance) due to a short channel is suppressed.

[0106] The length of the gate contact region 27 may be greater than or less than the width of the gate structure 15. The length of the gate contact region 27 may be greater than or less than the pitch of the gate structures 15. The length of the gate contact region 27 may be greater than or less than the pitch of two adjacent gate structures 15.

[0107] The interval between the multiple gate contact regions 27 may be greater than the width of the gate structures 15 or may be smaller than the width of the gate structures 15. The interval between the gate contact regions 27 may be greater than the pitch of the gate structures 15 or may be smaller than the pitch of the gate structures 15. The interval between the gate contact regions 27 may be greater than the pitch of two adjacent gate structures 15 or may be smaller than the pitch of two adjacent gate structures 15.

[0108] The plurality of gate contact regions 27 are respectively interposed in regions between the bottom walls of the plurality of gate structures 15 and the bottoms of the plurality of gate well regions 25. The plurality of gate contact regions 27 are connected to the bottom walls of the corresponding gate structures 15 and the corresponding gate well regions 25.

[0109] The plurality of gate contact regions 27 increase the p-type impurity concentration at the upper end of the corresponding gate well region 25. The gate contact regions 27 extend from the region directly below the gate structure 15 to both sides of the gate structure 15 and have extensions that extend along the sidewalls of the gate structure 15.

[0110] The thickness in the horizontal direction (first direction X) of the portion (extension) of the gate contact region 27 that runs along the side wall of the gate structure 15 may be less than the thickness in the vertical direction Z of the portion of the gate contact region 27 that runs along the bottom wall of the gate structure 15.

[0111] The extension of the gate contact region 27 is electrically connected to the body region 10 in the surface layer portion of the first main surface 3, and electrically connects the corresponding gate well region 25 to the body region 10. This prevents the gate well region 25 from being electrically floating, and improves the electrical response characteristics of the gate well region 25.

[0112] The gate contact region 27 has an upper end exposed from the first main surface 3. In this embodiment, the upper end of the gate contact region 27 is exposed from the sidewall of the first trench 16 at the opening end of the first trench 16. The upper end of the gate contact region 27 may extend horizontally in the surface portion of the body region 10.

[0113] The second semiconductor region 7 of the semiconductor device 1A includes a stacked structure of a base region 71 and a high concentration region 72 .

[0114] The base region 71 is formed closer to the second main surface 4 than the gate well region 25 and away from the body region 10. The base region 71 is formed in a layer shape extending along the first main surface 3 at a position away from the body region 10 and the first trench 16 toward the second main surface 4. The base region 71 is formed over the entire surface layer portion of the second semiconductor region 7 on the second main surface 4 side, and may be exposed from the first to fourth side surfaces 5A to 5D. The base region 71 forms a boundary surface between the second semiconductor region 7 and the first semiconductor region 6.

[0115] The thickness of the base region 71 may be, for example, not less than 0.5 μm and not more than 20 μm, and is preferably not less than 1 μm and not more than 10 μm.

[0116] The n-type impurity concentration of the base region 71 is preferably lower than the n-type impurity concentration of the first semiconductor region 6. The base region 71 has a dopant concentration of 1×10 １６ cm －３ 1x10 or more １７ cm －３The n-type impurity concentration of the base region 71 may have a peak value of the following: The n-type impurity concentration of the base region 71 may be substantially constant in the thickness direction. Of course, the n-type impurity concentration of the base region 71 may have a concentration gradient that gradually increases and / or decreases in the thickness direction (crystal growth direction) of the chip 2.

[0117] The high concentration region 72 is formed between the base region 71 and the body region 10, on the side of the first trench 16 and the gate well region 25. The high concentration region 72 is in contact with the body region 10 and the gate well region 25 and is formed in a layer shape extending along the first main surface 3. The high concentration region 72 is formed in the entire surface layer portion of the second semiconductor region 7 on the first main surface 3 side, and may be exposed from the first to fourth side surfaces 5A to 5D. In this embodiment, the high concentration region 72 forms a boundary surface between the second semiconductor region 7 and the body region 10.

[0118] The thickness of the high concentration region 72 may be 0.1 μm or more and 0.5 μm or less, and is preferably 0.15 μm or more and 0.4 μm or less.

[0119] The n-type impurity concentration of the high concentration region 72 is preferably higher than the n-type impurity concentration of the base region 71. The high concentration region 72 has a concentration of 1×10 １７ cm －３ 1x10 or more １８ cm －３ The n-type impurity concentration of the high-concentration region 72 may have a peak value of the following: The n-type impurity concentration of the high-concentration region 72 may be substantially constant in the thickness direction. Of course, the n-type impurity concentration of the high-concentration region 72 may have a concentration gradient that gradually increases and / or decreases in the thickness direction (crystal growth direction) of the chip 2.

[0120] In this embodiment, the n-type impurity concentrations of the base region 71 and the high-concentration region 72 are adjusted by nitrogen. The base region 71 and the high-concentration region 72 may have n-type impurity concentrations adjusted by at least one pentavalent element. For example, the n-type impurity concentrations of the base region 71 and the high-concentration region 72 may be adjusted by at least one of nitrogen, phosphorus, arsenic, antimony, and bismuth.

[0121] 9, the outermost gate structure 15 among the plurality of gate structures 15 is a terminal gate structure 15A. In this embodiment, the plurality of gate structures 15 arranged in stripes extending along the second direction Y have one terminal gate structure 15A formed at the end of each of both sides (the third side surface 5C side and the fourth side surface 5D side) in the first direction X (see also FIGS. 3 and 4). In FIG. 9, the terminal gate structure 15A on the fourth side surface 5D side is shown.

[0122] In this embodiment, the terminal gate structure 15A includes a terminal first trench 16A, a terminal first insulating film 17A, and a terminal first buried electrode 18A. The terminal first trench 16A is a boundary trench that forms a peripheral boundary 19, which is the boundary between the active region 8 and the peripheral region 9. The terminal gate structure 15A has the same structure as the remaining gate structures 15, except for its arrangement in stripes.

[0123] 6 and 9 to 11 , semiconductor device 1A includes a p-type outer well region 40 formed in a surface layer portion of first main surface 3 in peripheral region 9. A source potential is applied to outer well region 40. Outer well region 40 has a p-type impurity concentration higher than the n-type impurity concentration of second semiconductor region 7.

[0124] The p-type impurity concentration of the outer well region 40 is lower than the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the outer well region 40 is lower than the p-type impurity concentration of the gate contact region 27.

[0125] The p-type impurity concentration of the outer well region 40 may be approximately equal to the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the outer well region 40 may be higher than the p-type impurity concentration of the gate well region 25, or may be lower than the p-type impurity concentration of the gate well region 25.

[0126] The p-type impurity concentration of the outer well region 40 may be approximately equal to the p-type impurity concentration of the body region 10. It may be higher than the p-type impurity concentration of the body region 10, or may be lower than the p-type impurity concentration of the body region 10.

[0127] As described above, the outer well region 40 includes a first outer well region 42 and a plurality of second outer well regions 43. The first outer well region 42 and the plurality of second outer well regions 43 may be referred to as a "termination region" and a "field region," respectively. The first outer well region 42 and the plurality of second outer well regions 43 may also be collectively referred to as an "outer well region." The first outer well region 42 may also be referred to as a "termination well region," a "Junction Termination Extension region (JTE region)," or the like. The second outer well region 43 may also be referred to as a "guard region," a "field limit region," or the like.

[0128] A source potential is applied to the first outer well region 42. The first outer well region 42 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7.

[0129] 9 and 10 , the first outer well region 42 is formed in a surface layer portion of the second semiconductor region 7 and is electrically connected to the second semiconductor region 7. The first outer well region 42 is formed at a distance from the bottom of the second semiconductor region 7 toward the first main surface 3, and faces the first semiconductor region 6 across a part of the second semiconductor region 7. The first outer well region 42 is preferably formed at a distance from a depth position in the middle of the second semiconductor region 7 toward the first main surface 3.

[0130] The first outer well region 42 is formed deeper than the gate well region 25 along the outer boundary 19. The depth D1 of the first outer well region 42 may be, for example, greater than 0 μm and less than 4 μm. The depth D1 of the first outer well region 42 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 0.75 μm, 0.75 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, 1.75 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, and 3.5 μm to 4 μm.

[0131] When the first outer well region 42 is disposed at a distance from the first main surface 3 toward the bottom of the second semiconductor region 7 (when the first outer well region 42 is not exposed from the first main surface 3), the depth D1 of the first outer well region 42 may be referred to as the thickness of the first outer well region 42. Furthermore, the first outer well region 42 may have approximately the same depth as the gate well region 25.

[0132] In the horizontal direction along the first main surface 3, the first outer well region 42 at least partially covers the gate well region 25 of the terminal first trench 16A.

[0133] More specifically, the gate well region 25 includes a well side portion (in this embodiment, a bulging portion 25 a) extending in the thickness direction of the second semiconductor region 7, and a well bottom portion 25 b extending from the bulging portion 25 a in a direction along the first main surface 3. The first outer well region 42 selectively covers the bulging portion 25 a on the outer peripheral region 9 side (outside) of the gate well region 25 of the terminal first trench 16A. The bulging portion 25 a and the well bottom 25 b on the active region 8 side (inside) that are not covered by the first outer well region 42 are covered by the second semiconductor region 7 (in this embodiment, a high-concentration region 72).

[0134] The first outer well region 42 has a first upper end 42a on the first main surface 3 side, a first lower end 42b on the opposite side, and a first main body portion 42c between the first lower end 42b and the first upper end 42a.

[0135] The first upper end 42a extends horizontally along the first main surface 3 and is exposed from the first main surface 3. The first upper end 42a is located on the first main surface 3 side with respect to the depth position of the bottom of the gate structure 15. The first upper end 42a is located on the first main surface 3 side with respect to the depth position of the bottom of the gate well region 25. The first upper end 42a is located on the first main surface 3 side with respect to the depth position of the bottom of the body region 10. The first upper end 42a is located on the first main surface 3 side with respect to the depth position of a boundary 62 between the high-concentration region 72 and the base region 71.

[0136] The first upper end 42a is formed in a shape that protrudes in an arc from the first body portion 42c toward the first main surface 3. The first upper end 42a includes a central portion 63 exposed from the first main surface 3, and an end 64 that is disposed at a position spaced from the first main surface 3 toward the bottom of the second semiconductor region 7.

[0137] A gap 65 is formed between an end 64 of the first upper end 42a and the first main surface 3. The gap 65 is a region defined between the flat first main surface 3 and the arc-shaped first upper end 42a. A part of the second semiconductor region 7 (in this embodiment, the base region 71) fits into the gap 65. This part of the second semiconductor region 7 is sandwiched between the first main surface 3 and the first upper end 42a.

[0138] The first lower end 42b extends horizontally along the first main surface 3 and forms a pn junction with the second semiconductor region 7. In this embodiment, the first lower end 42b forms a pn junction with the base region 71. The first lower end 42b is located on the bottom side of the second semiconductor region 7 relative to the depth position of the bottom of the gate structure 15. The first lower end 42b is located on the bottom side of the second semiconductor region 7 relative to the depth position of the bottom of the gate well region 25. The first lower end 42b is located on the bottom side of the second semiconductor region 7 relative to the depth position of the bottom of the body region 10.

[0139] The first lower end 42b is formed in a flat shape that is approximately parallel to the first main surface 3. The first lower end 42b may be formed in a flat shape that extends in a direction perpendicular to the thickness direction of the second semiconductor region 7.

[0140] The first body portion 42c is sandwiched between the first upper end portion 42a and the first lower end portion 42b. The first body portion 42c may be a portion of the first outer well region 42 that covers the gate structure 15 and the gate well region 25.

[0141] The first body portion 42c includes a first side portion 42d connecting the first upper end portion 42a and the first lower end portion 42b. In this embodiment, the first side portion 42d is inclined toward the active region 8 from the first upper end portion 42a toward the first lower end portion 42b. For example, the first outer well region 42 may be formed in a mesa shape in cross section, having the first side portion 42d inclined such that the width W1 narrows from the first upper end portion 42a toward the first lower end portion 42b.

[0142] The first outer well region 42 has a width W1 (for example, the width of the first lower end 42b) that is larger than the width of the gate structure 15. The width W1 of the first outer well region 42 is larger than the width of the terminal gate structure 15A. The width W1 of the first outer well region 42 may be larger than the total width of the multiple terminal gate structures 15A. The width W1 of the first outer well region 42 may be larger than the total width of the multiple gate well regions 25.

[0143] The width W1 of the first outer well region 42 may be greater than 0 μm and less than 300 μm. The width W1 of the first outer well region 42 may have a value belonging to at least one of the ranges of greater than 0 μm and less than 25 μm, 25 μm to 50 μm, 50 μm to 75 μm, 75 μm to 100 μm, 100 μm to 125 μm, 125 μm to 150 μm, 150 μm to 175 μm, 175 μm to 200 μm, 200 μm to 225 μm, 225 μm to 250 μm, 250 μm to 275 μm, and 275 μm to 300 μm.

[0144] When a reverse bias voltage is applied, the first outer well region 42 spreads a depletion layer into the second semiconductor region 7. The depletion layer originating in the first outer well region 42 spreads in the horizontal and thickness directions, and relieves the electric field in the vicinity of the peripheral boundary 19 between the active region 8 and the peripheral region 9.

[0145] The first outer well region 42 of the semiconductor device 1A includes a stacked structure of a first region 12 and a second region 13. The stacked structure may be a two-layer structure including a lower layer made of the first region 12 and an upper layer made of the second region 13. The first region 12 may be referred to as a "base region," "base layer," etc. The second region 13 may be referred to as a "high concentration region," "high concentration layer," "outer body region," etc.

[0146] The first region 12 is formed closer to the second main surface 4 than the bottom of the body region 10 and away from the first main surface 3. The first region 12 is formed in a layer shape extending along the first main surface 3 at a position away from the first main surface 3 toward the second main surface 4. The first region 12 may be formed over the entire surface layer portion of the first outer well region 42 on the second main surface 4 side, and exposed from the first side portion 42d of the first outer well region 42. In other words, the first region 12 may have an outer end portion 12a located on the first side portion 42d (outer end portion) of the first outer well region 42.

[0147] The first region 12 may be formed to cross the bottom of the first trench 16 in the thickness direction of the second semiconductor region 7. The first region 12 may have an upper portion on the first main surface 3 side and a lower portion on the second main surface 4 side relative to the bottom of the first trench 16. The first region 12 may at least partially cover the gate well region 25 of the terminal first trench 16A.

[0148] An inner end 12b of the first region 12 forms a pn junction with the high concentration region 72. More specifically, the first region 12 may have a bottom 12c at the same depth as the bottom of the high concentration region 72, and may be in contact with the high concentration region 72 on its side and the base region 71 below.

[0149] The thickness of the first region 12 may be, for example, not less than 0.5 μm and not more than 5.0 μm, and is preferably not less than 1.0 μm and not more than 3.0 μm.

[0150] The p-type impurity concentration of the first region 12 may be lower than the p-type impurity concentration of the gate contact region 27. The p-type impurity concentration of the first region 12 may be higher than the p-type impurity concentration of the gate well region 25, or may be lower than the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the first region 12 may be lower than the p-type impurity concentration of the body region 10. The first region 12 has a p-type impurity concentration of 1×10 １６ cm －３ 1x10 or more １７ cm －３ The p-type impurity concentration may have the following peak value:

[0151] The second region 13 is formed closer to the first main surface 3 than the bottom of the body region 10 and is exposed from the first main surface 3. The second region 13 is formed in a layer extending along the first main surface 3. The second region 13 may be formed over the entire surface layer portion of the first outer well region 42 on the first main surface 3 side and exposed from the first side portion 42d of the first outer well region 42. In other words, the second region 13 may have an outer end portion 13a located on the first side portion 42d (outer end portion) of the first outer well region 42. As a result, the first outer well region 42 may have a layer structure in which the first region 12 having an annular shape in a planar view and the second region 13 having an annular shape in a planar view are stacked.

[0152] 12, the second region 13 may be an outer body region drawn out from the body region 10 toward the outer periphery region 9. In this embodiment, the second region 13 is drawn out from the body region 10 between adjacent gate structures 15 and formed in a ring shape surrounding the striped gate structures 15. In FIG. 12, the second region 13 (outer body region) is indicated by hatching.

[0153] The second region 13 may be formed closer to the first main surface 3 than the bottom of the first trench 16 in the thickness direction of the second semiconductor region 7. In this embodiment, the second region 13 forms the first upper end 42 a of the first outer well region 42.

[0154] The thickness of the second region 13 may be, for example, not less than 0.1 μm and not more than 1 μm, and is preferably not less than 0.1 μm and not more than 0.5 μm.

[0155] The p-type impurity concentration of the second region 13 may be lower than the p-type impurity concentration of the gate contact region 27. The p-type impurity concentration of the second region 13 may be higher than the p-type impurity concentration of the gate well region 25, or may be lower than the p-type impurity concentration of the gate well region 25. In this embodiment, the p-type impurity concentration of the second region 13 is equal to the p-type impurity concentration of the body region 10. The second region 13 has a p-type impurity concentration of 1×10 １７ cm －３ 1x10 or more １８ cm －３ The p-type impurity concentration may have the following peak value:

[0156] The semiconductor device 1A includes a p-type outer contact region 41 formed in the peripheral region 9 in a surface layer portion of the first main surface 3. A source potential is applied to the outer contact region 41. The outer contact region 41 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7 (high-concentration region 72). The p-type impurity concentration of the outer contact region 41 is higher than the p-type impurity concentrations of the body region 10 and the second region 13 of the first outer well region 42.

[0157] The p-type impurity concentration of the outer contact region 41 is higher than the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the outer contact region 41 may be approximately equal to the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the outer contact region 41 may be lower than the p-type impurity concentration of the gate well region 25.

[0158] The p-type impurity concentration of the outer contact region 41 may be approximately equal to the p-type impurity concentration of the gate contact region 27. The p-type impurity concentration of the outer contact region 41 may be higher than the p-type impurity concentration of the gate contact region 27, or may be lower than the p-type impurity concentration of the gate contact region 27.

[0159] The outer contact region 41 is formed in a surface layer portion of the first outer well region 42. That is, the outer contact region 41 is formed in a thickness range between the first main surface 3 and the bottom of the first outer well region 42. In this embodiment, the outer contact region 41 is selectively formed in the first upper end portion 42a of the first outer well region 42. The outer contact region 41 is selectively formed in a surface layer portion of the second region 13 of the first outer well region 42. The outer contact region 41 is formed on the first main surface 3 side of the boundary 60 between the first region 12 and the second region 13, and away from the boundary 60. The p-type impurity concentration of the first outer well region 42 is increased, thereby improving the electrical response speed of the first outer well region 42.

[0160] The outer contact region 41 extends in a strip shape along the terminal gate structure 15A in the second direction Y. The outer contact region 41 extends in a strip shape across the plurality of gate structures 15 in the first direction X.

[0161] In this embodiment, the outer contact region 41 is formed in a polygonal ring shape (a square ring shape in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view, and surrounds the inner portion (active region 8) of the first main surface 3. The outer contact region 41 may have an edge portion that connects the portion extending in the first direction X and the portion extending in the second direction Y in an arc shape (preferably a quadrant arc shape).

[0162] A plurality of outer contact regions 41 may be formed at intervals along the direction in which the terminal gate structure 15A extends and the direction crossing the plurality of gate structures 15A.

[0163] The outer contact region 41 has a width less than that of the first outer well region 42, and is formed within the first outer well region 42. The outer contact region 41 has an inner edge portion on the inner side of the first main surface 3 (the active region 8 side) and an outer edge portion on the peripheral side of the first main surface 3.

[0164] In this embodiment, the inner edge of the outer contact region 41 is connected to the terminal gate structure 15A. In this embodiment, the inner edge of the outer contact region 41 is connected to the gate well region 25 of the terminal first trench 16A. The inner edge of the outer contact region 41 extends along the terminal gate structure 15A (peripheral boundary 19) in the thickness direction of the second semiconductor region 7 and is connected to the gate well region 25 of the terminal first trench 16A. The first outer well region 42 is electrically connected to the body region 10 via the gate well region 25 of the terminal first trench 16A.

[0165] The first outer well region 42 may be formed at a distance from the terminal gate structure 15A. A boundary 60 between the first region 12 and the second region 13 extends from the inner edge of the outer contact region 41 along the first main surface 3 to a first side portion 42d, dividing the first outer well region 42 into upper and lower two.

[0166] The outer edge of the outer contact region 41 is formed at a distance from the outer edge of the first outer well region 42 toward the terminal gate structure 15A. The outer contact region 41 may have a portion that crosses the outer edge of the first outer well region 42 and is connected to the second semiconductor region 7.

[0167] The outer contact region 41 has a width greater than the width of the gate well region 25. The width of the outer contact region 41 is greater than the width of the terminal gate structure 15A. The width of the outer contact region 41 may be less than the width of the first outer well region 42. The width of the outer contact region 41 may be greater than the width of the first outer well region 42.

[0168] The width of the outer contact region 41 may be greater than 0 μm and less than 300 μm. The width of the outer contact region 41 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than 25 μm, 25 μm to 50 μm, 50 μm to 75 μm, 75 μm to 100 μm, 100 μm to 125 μm, 125 μm to 150 μm, 150 μm to 175 μm, 175 μm to 200 μm, 200 μm to 225 μm, 225 μm to 250 μm, 250 μm to 275 μm, and 275 μm to 300 μm.

[0169] The outer contact region 41 has an upper end located on the first main surface 3 side and a bottom located on the bottom side of the first outer well region 42. The upper end of the outer contact region 41 is exposed from the first main surface 3. The bottom of the outer contact region 41 is located on the first main surface 3 side with respect to the depth position of the bottom of the gate well region 25.

[0170] The bottom of the outer contact region 41 is located closer to the first main surface 3 than the depth position of the bottom of the first outer well region 42. The bottom of the outer contact region 41 may be located closer to the first main surface 3 than the depth position of the bottom of the body region 10, or may be located closer to the bottom of the first outer well region 42.

[0171] The depth (thickness) of the outer contact region 41 may be greater than 0 μm and less than or equal to 1 μm. The depth of the outer contact region 41 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than or equal to 0.1 μm, 0.1 μm to 0.2 μm, 0.2 μm to 0.3 μm, 0.3 μm to 0.4 μm, 0.4 μm to 0.5 μm, 0.5 μm to 0.6 μm, 0.6 μm to 0.7 μm, 0.7 μm to 0.8 μm, 0.8 μm to 0.9 μm, and 0.9 μm to 1 μm.

[0172] The second outer well region 43 is formed in an electrically floating state. A source potential may be applied to the second outer well region 43.

[0173] The number of second outer well regions 43 is arbitrary. The number of second outer well regions 43 may be 1 or more and 15 or less. The number of second outer well regions 43 may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. The number of second outer well regions 43 is typically 1 or more and 10 or less. In this embodiment, the semiconductor device 1A includes, as an example, four second outer well regions 43.

[0174] The second outer well region 43 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the second outer well region 43 may be approximately equal to the p-type impurity concentration of the first outer well region 42. The p-type impurity concentration of the second outer well region 43 may be higher than the p-type impurity concentration of the first outer well region 42, or may be lower than the p-type impurity concentration of the first outer well region 42.

[0175] The p-type impurity concentration of the second outer well region 43 may be lower than the p-type impurity concentration of the gate contact region 27. The p-type impurity concentration of the second outer well region 43 may be higher than the p-type impurity concentration of the gate well region 25, or may be lower than the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the second outer well region 43 may be higher than the p-type impurity concentration of the body region 10, or may be lower than the p-type impurity concentration of the body region 10.

[0176] In this embodiment, the p-type impurity concentrations of the second outer well regions 43 are approximately equal to each other. The p-type impurity concentrations of the second outer well regions 43 are arbitrary and can take various values ​​depending on the electric field to be relaxed. The p-type impurity concentrations of the second outer well regions 43 may also be different from each other.

[0177] 10 and 11 , the plurality of second outer well regions 43 are formed in a surface layer portion of the second semiconductor region 7 and are electrically connected to the second semiconductor region 7. The plurality of second outer well regions 43 are formed at intervals from the bottom of the second semiconductor region 7 toward the first main surface 3, and face the first semiconductor region 6 across a part of the second semiconductor region 7. The plurality of second outer well regions 43 are preferably formed at intervals from a depth position in the middle of the second semiconductor region 7 toward the first main surface 3.

[0178] The depth D2 of the second outer well region 43 may be approximately equal to the depth D1 of the first outer well region 42. The depth D2 of the second outer well region 43 may be deeper than the depth D1 of the first outer well region 42, or may be shallower than the depth D1 of the first outer well region 42.

[0179] The depth D2 of the second outer well region 43 may be, for example, greater than 0 μm and less than or equal to 4 μm. The depth D2 of the second outer well region 43 may have a value belonging to at least one of the ranges of greater than 0 μm and less than or equal to 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 0.75 μm, 0.75 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, 1.75 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, and 3.5 μm to 4 μm. When the second outer well region 43 is spaced apart from the first main surface 3 toward the bottom of the second semiconductor region 7 (when the second outer well region 43 is not exposed from the first main surface 3), the depth D2 of the second outer well region 43 may also be referred to as the thickness of the second outer well region 43.

[0180] In this embodiment, the depths D2 of the second outer well regions 43 are approximately equal to each other. The depths D2 of the second outer well regions 43 are arbitrary and can take various values ​​depending on the electric field to be relaxed. The depths D2 of the second outer well regions 43 may also be different from each other.

[0181] The depth D2 of the multiple second outer well regions 43 may increase sequentially toward the peripheral edge of the first main surface 3. The depth D2 of the multiple second outer well regions 43 may increase toward the peripheral edge of the first main surface 3 in units of two or more groups, each group including two or more second outer well regions 43.

[0182] The depth D2 of the multiple second outer well regions 43 may decrease in order toward the peripheral edge of the first main surface 3. The depth D2 of the multiple second outer well regions 43 may decrease toward the peripheral edge of the first main surface 3 in units of two or more groups, each group including two or more second outer well regions 43.

[0183] The second outer well regions 43 are formed at intervals in the region between the periphery of the first main surface 3 and the terminal gate structure 15A (peripheral boundary portion 19). The second outer well regions 43 are formed at intervals in the region between the periphery of the first main surface 3 and the first outer well region 42.

[0184] The second outer well region 43 has a second upper end 43a on the first main surface 3 side, a second lower end 43b on the opposite side, and a second main body portion 43c between the second lower end 43b and the second upper end 43a.

[0185] The second upper end 43a extends horizontally along the first main surface 3 and is exposed from the first main surface 3. The second upper end 43a is located on the first main surface 3 side with respect to the depth position of the bottom of the gate structure 15. The second upper end 43a is located on the first main surface 3 side with respect to the depth position of the bottom of the gate well region 25. The second upper end 43a is located on the first main surface 3 side with respect to the depth position of the bottom of the body region 10. The second upper end 43a is located on the first main surface 3 side with respect to the depth position of a boundary 62 between the high-concentration region 72 and the base region 71.

[0186] The second upper end 43a is formed in a shape that protrudes in an arc from the second body portion 43c toward the first main surface 3. The second upper end 43a includes a central portion 66 exposed from the first main surface 3, and an end portion 67 that is disposed at a position spaced from the first main surface 3 toward the bottom of the second semiconductor region 7.

[0187] A gap 68 is formed between an end 67 of the second upper end 43a and the first main surface 3. The gap 68 is a region defined between the flat first main surface 3 and the arc-shaped second upper end 43a. A part of the second semiconductor region 7 (in this embodiment, the base region 71) fits into the gap 68. This part of the second semiconductor region 7 is sandwiched between the first main surface 3 and the second upper end 43a.

[0188] The second lower end 43b extends horizontally along the first main surface 3 and forms a pn junction with the second semiconductor region 7. In this embodiment, the second lower end 43b forms a pn junction with the base region 71. The second lower end 43b is located on the bottom side of the second semiconductor region 7 with respect to the depth position of the bottom of the gate structure 15. The second lower end 43b is located on the bottom side of the second semiconductor region 7 with respect to the depth position of the bottom of the gate well region 25. The second lower end 43b is located on the bottom side of the second semiconductor region 7 with respect to the depth position of the bottom of the body region 10. The second lower end 43b is located on the bottom side of the second semiconductor region 7 with respect to the depth position of the boundary 62 between the high-concentration region 72 and the base region 71.

[0189] The second lower end 43b is formed in a flat shape that is approximately parallel to the first main surface 3. The second lower end 43b may be formed in a flat shape that extends in a direction perpendicular to the thickness direction of the second semiconductor region 7.

[0190] The second main body portion 43c is sandwiched between the second upper end portion 43a and the second lower end portion 43b. The second main body portion 43c includes a second side portion 43d connecting the second upper end portion 43a and the second lower end portion 43b. In this embodiment, the second side portion 43d is inclined from the second upper end portion 43a toward the second lower end portion 43b. For example, the second outer well region 43 may be formed in a mesa shape in cross section, having the second side portion 43d inclined such that the width W2 narrows from the second upper end portion 43a toward the second lower end portion 43b.

[0191] The plurality of second outer well regions 43 may have a width W2 that is less than the width W1 of the first outer well region 42. The width W2 of the plurality of second outer well regions 43 (for example, the width of the second lower end portion 43b) may be smaller than the width of the gate structure 15 or may be larger than the width of the gate structure 15. The width W2 of the second outer well region 43 may be smaller than the width of the gate well region 25 or may be larger than the width of the gate well region 25.

[0192] In this embodiment, the widths W2 of the second outer well regions 43 are approximately equal to each other. The widths W2 of the second outer well regions 43 are arbitrary and can take various values ​​depending on the electric field to be relaxed. The widths W2 of the second outer well regions 43 may also be different from each other.

[0193] The widths W2 of the multiple second outer well regions 43 may increase sequentially toward the peripheral edge of the first main surface 3. The widths W2 of the multiple second outer well regions 43 may increase toward the peripheral edge of the first main surface 3 in units of two or more groups, each group including two or more second outer well regions 43.

[0194] The widths W2 of the multiple second outer well regions 43 may decrease in order toward the peripheral edge of the first main surface 3. The widths W2 of the multiple second outer well regions 43 may decrease toward the peripheral edge of the first main surface 3 in units of two or more groups, each group including two or more second outer well regions 43.

[0195] The width W2 of the second outer well region 43 is narrower than the width W1 of the first outer well region 42. The width W2 of the second outer well region 43 may be greater than 0 μm and less than 5 μm. The width W2 of the second outer well region 43 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 0.75 μm, 0.75 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, 1.75 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, 3.5 μm to 4 μm, 4 μm to 4.5 μm, and 4.5 μm to 5 μm.

[0196] The spacing between the multiple second outer well regions 43 may be equal to or less than the width W2 of the second outer well regions 43. The spacing between the multiple second outer well regions 43 is preferably less than the width W2 of the second outer well regions 43. The spacing between the multiple second outer well regions 43 may be greater than the width W2 of the second outer well regions 43.

[0197] In this embodiment, the intervals between the second outer well regions 43 are approximately equal to each other. The intervals between the second outer well regions 43 are arbitrary and can take various values ​​depending on the electric field to be relaxed. The intervals between the second outer well regions 43 may also be different from each other.

[0198] The spacing between the multiple second outer well regions 43 may increase sequentially toward the peripheral edge of the first main surface 3. The spacing between the multiple second outer well regions 43 may increase toward the peripheral edge of the first main surface 3 in units of two or more groups, each group including two or more second outer well regions 43.

[0199] The intervals between the multiple second outer well regions 43 may decrease in order toward the periphery of the first main surface 3. The intervals between the multiple second outer well regions 43 may decrease toward the periphery of the first main surface 3 in units of two or more groups, each group including two or more second outer well regions 43.

[0200] The spacing between the second outer well regions 43 may be greater than 0 μm and less than 5 μm. The spacing may have a value belonging to at least one of the ranges of greater than 0 μm and less than 0.5 μm, 0.5 μm to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, 3.5 μm to 4 μm, 4 μm to 4.5 μm, and 4.5 μm to 5 μm.

[0201] The ratio of the spacing of the second outer well region 43 to the width W2 of the second outer well region 43 (spacing ratio) may be 0.1 or more and 5 or less. The spacing ratio may have a value belonging to at least one of the ranges of 0.1 or more and 0.5 or less, 0.5 or more and 1 or less, 1 or more and 1.5 or less, 1.5 or more and 2 or less, 2 or more and 2.5 or less, 2.5 or more and 3 or less, 3 or more and 3.5 or less, 3.5 or more and 4 or less, 4 or more and 4.5 or less, and 4.5 or more and 5 or less.

[0202] The second outer well regions 43 expand the depletion layer into the second semiconductor region 7 when a reverse bias voltage is applied. The depletion layer originating in the second outer well regions 43 expands in the horizontal and thickness directions and merges with the depletion layer originating in the first outer well region 42. The second outer well regions 43 expand the depletion layer originating in the first outer well region 42 toward the periphery of the first main surface 3, thereby alleviating the electric field in the periphery (peripheral region 9) of the first main surface 3.

[0203] The semiconductor device 1A includes a main surface insulating film 45 that selectively covers the first main surface 3. The main surface insulating film 45 may include at least one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. The main surface insulating film 45 preferably includes the same type of insulating material as the first insulating film 17. In this embodiment, the main surface insulating film 45 has a single-layer structure made of a silicon oxide film. It is particularly preferable that the main surface insulating film 45 includes a silicon oxide film made of an oxide of the chip 2.

[0204] The main surface insulating film 45 is connected to the first insulating films 17 of the plurality of gate structures 15 in the active region 8 , and exposes the first buried electrodes 18 of the plurality of gate structures 15 .

[0205] The main surface insulating film 45 covers the second semiconductor region 7, the first outer well region 42, the outer contact region 41, and the second outer well region 43 in the peripheral region 9. In this embodiment, the main surface insulating film 45 is continuous with the first to fourth side surfaces 5A to 5D in the peripheral portion of the first main surface 3. The main surface insulating film 45 may be formed at a distance inward from the peripheral portion of the first main surface 3, exposing the peripheral portion of the first main surface 3 (the second semiconductor region 7).

[0206] The semiconductor device 1A includes an insulating interlayer film 47 that selectively covers the first main surface 3 with the main surface insulating film 45 sandwiched therebetween. The interlayer film 47 may also be referred to as an "insulating film," an "interlayer insulating film," an "intermediate insulating film," or the like. The interlayer film 47 may include at least one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. The interlayer film 47 preferably includes a silicon oxide film.

[0207] The interlayer film 47 covers the plurality of gate structures 15 (first buried electrodes 18) on the active region 8 side. The interlayer film 47 covers the second semiconductor region 7, the first outer well region 42, the outer contact region 41, and the second outer well region 43 on the peripheral region 9 side, with the main surface insulating film 45 sandwiched therebetween.

[0208] In this embodiment, the interlayer film 47 is continuous with the first to fourth side surfaces 5A to 5D at the peripheral portion of the first main surface 3. The interlayer film 47 may be formed at a distance inward from the peripheral portion of the first main surface 3, exposing the peripheral portion of the first main surface 3 (the second semiconductor region 7).

[0209] The interlayer film 47 may have a thickness of 0.5 μm or more and 3 μm or less. The thickness of the interlayer film 47 may have a value belonging to at least one of the ranges of 0.5 μm or more and 1 μm or less, 1 μm or more and 1.5 μm or less, 1.5 μm or more and 2 μm or less, 2 μm or more and 2.5 μm or less, and 2.5 μm or more and 3 μm or less.

[0210] The semiconductor device 1A includes a plurality of gate openings (not shown) formed in the interlayer film 47 in the active region 8. The plurality of gate openings are formed in a one-to-many correspondence with a corresponding one of the gate structures 15. In this embodiment, the plurality of gate openings penetrate the interlayer film 47 and expose one end or the other end of each of the plurality of gate structures 15 (first buried electrodes 18).

[0211] The plurality of gate openings may each have an opening end curved in an arc shape. The plurality of gate openings may be formed in a quadrangular shape, a rectangular shape (strip shape) extending in the first direction X, a rectangular shape (strip shape) extending in the second direction Y, a circular shape, or the like in a plan view. The plurality of gate openings may each have an opening end curved in an arc shape.

[0212] The semiconductor device 1A includes a plurality of source openings 49 formed in the interlayer film 47 in the active region 8. For clarity, the source openings 49 are omitted from FIG. 10 . The source openings 49 are formed in portions of the interlayer film 47 that cover the active region 8. In this embodiment, the source openings 49 are formed in regions between adjacent gate structures 15, respectively, and expose the source regions 11 and the gate contact regions 27, respectively.

[0213] The plurality of source openings 49 penetrate the main surface insulating film 45 and the interlayer film 47, and expose the corresponding plurality of source regions 11 and the corresponding plurality of gate contact regions 27. Each of the plurality of source openings 49 may have an opening end that is curved in an arc shape.

[0214] The source openings 49 may be formed in a one-to-many correspondence with the regions between adjacent gate structures 15. In this case, the source openings 49 may be formed at intervals along the regions between the corresponding gate structures 15. In this case, the source openings 49 may be formed in a quadrangular, rectangular (strip-like), circular, or other shape in plan view.

[0215] The semiconductor device 1A includes at least one outer opening 50 (one in this embodiment) formed in the interlayer film 47 in the peripheral region 9. The outer opening 50 penetrates the main surface insulating film 45 and the interlayer film 47 to expose the outer contact region 41. The outer opening 50 extends in a strip shape along the outer contact region 41 in a plan view.

[0216] In this embodiment, the outer opening 50 is formed in a polygonal ring shape (specifically, a square ring shape) in plan view that surrounds the inner portion (active region 8) of the first main surface 3 along the outer contact region 41. The outer opening 50 may have an opening end that is curved in an arc shape.

[0217] The semiconductor device 1A may have a plurality of outer openings 50. In this case, the plurality of outer openings 50 may be formed at intervals along the outer contact region 41 so as to surround the inner portion (active region 8) of the first main surface 3. In this case, the plurality of outer openings 50 may be formed in a quadrangular (square), rectangular, hexagonal, circular, or other shape in plan view.

[0218] The semiconductor device 1A includes a source electrode 51 disposed on the first main surface 3. The source electrode 51 extends from above the interlayer film 47 into the plurality of source openings 49, and is electrically connected to the plurality of source regions 11 and the plurality of gate contact regions 27 within the plurality of source openings 49.

[0219] In this embodiment, the source electrode 51 has a layered structure including a lower electrode film 52 and a main electrode film 53, which are layered in this order from the chip 2 side. In this embodiment, the lower electrode film 52 has a layered structure including a first electrode film and a second electrode film. In this embodiment, the first electrode film includes a Ti film, and the second electrode film includes a TiN film. The lower electrode film 52 does not necessarily have to have a layered structure, and may have a single-layer structure consisting of either the first electrode film (Ti film) or the second electrode film (TiN film).

[0220] The lower electrode film 52 collectively covers the region of the interlayer film 47 where the plurality of source openings 49 are formed, and extends into the plurality of source openings 49 from above the interlayer film 47. The lower electrode film 52 has a portion that covers the insulating main surface of the interlayer film 47 in a film-like manner, a portion that covers the wall surfaces of the plurality of source openings 49 in a film-like manner, and a portion that covers the first main surface 3 in the plurality of source openings 49. The lower electrode film 52 is mechanically and electrically connected to the plurality of source regions 11 and the plurality of gate contact regions 27 in the source openings 49.

[0221] The main electrode film 53 contains a different conductive material from that of the lower electrode film 52. The main electrode film 53 may contain at least one of an Al film, an Al alloy film, a Cu film, and a Cu alloy film. The Al alloy film may contain at least one of an AlSi alloy film, an AlCu alloy film, and an AlSiCu alloy film. The main electrode film 53 has a thickness greater than the thickness (total thickness) of the lower electrode film 52. The thickness of the main electrode film 53 is preferably greater than the thickness of the interlayer film 47.

[0222] The thickness of the main electrode film 53 may be 0.5 μm or more and 5 μm or less. The thickness of the main electrode film 53 may have a value belonging to at least one of the ranges of 0.5 μm or more and 1 μm or less, 1 μm or more and 1.5 μm or less, 1.5 μm or more and 2 μm or less, 2 μm or more and 2.5 μm or less, 2.5 μm or more and 3 μm or less, 3 μm or more and 3.5 μm or less, 3.5 μm or more and 4 μm or less, 4 μm or more and 4.5 μm or less, and 4.5 μm or more and 5 μm or less.

[0223] The main electrode film 53 directly covers the lower electrode film 52. The main electrode film 53 collectively covers the region of the interlayer film 47 where the plurality of source openings 49 are formed, and backfills the plurality of source openings 49.

[0224] The main electrode film 53 has a portion that covers the insulating main surface of the interlayer film 47 with the lower electrode film 52 sandwiched therebetween, a portion that covers the wall surfaces of the plurality of source openings 49 with the lower electrode film 52 sandwiched therebetween, and a portion that covers the first main surface 3 with the lower electrode film 52 sandwiched therebetween. The main electrode film 53 is electrically connected to the plurality of source regions 11 and the plurality of gate contact regions 27 via the lower electrode film 52 within the plurality of source openings 49.

[0225] The semiconductor device 1A includes a source wiring 56 disposed on the interlayer film 47 around the source electrode 51 .

[0226] The source wiring 56 is drawn from the active region 8 to the peripheral region 9, and has a portion facing the outer contact region 41 across the interlayer film 47. The source wiring 56 enters the outer opening 50 from above the interlayer film 47, and is electrically connected to the outer contact region 41 within the outer opening 50. In other words, the source wiring 56 is electrically connected to the first outer well region 42 via the outer contact region 41.

[0227] The source wiring 56 has an inner edge portion on the inner side (active region 8 side) of the first main surface 3 and an outer edge portion on the peripheral side of the first main surface 3. The inner edge portion of the source wiring 56 is located within the active region 8 and faces one or more (multiple in this embodiment) gate structures 15 with the interlayer film 47 interposed therebetween. The inner edge portion of the source wiring 56 faces at least the terminal gate structure 15A with the interlayer film 47 interposed therebetween.

[0228] The outer edge of the source wiring 56 is formed at a distance inward (toward the active region 8) from the periphery of the first main surface 3. The outer edge of the source wiring 56 is formed at a distance inward from the innermost second outer well region 43 among the plurality of second outer well regions 43. In other words, the source wiring 56 does not face the plurality of second outer well regions 43 across the interlayer film 47.

[0229] With this configuration, the electric field dispersion path is prevented from being blocked by the source wiring 56 in the region above the multiple second outer well regions 43, and the electric field (electric force lines) are appropriately dispersed by the multiple second outer well regions 43.

[0230] Like the source electrode 51, the source wiring 56 has a laminated structure including a lower electrode film 52 and a main electrode film 53 laminated in this order from the chip 2 side.

[0231] The lower electrode film 52 collectively covers the region of the interlayer film 47 where the outer opening 50 is formed, and extends into the outer opening 50 from above the interlayer film 47. The lower electrode film 52 has a portion that covers the insulating main surface of the interlayer film 47 in a film-like manner, a portion that covers the wall surface of the outer opening 50 in a film-like manner, and a portion that covers the first main surface 3 within the outer opening 50 in a film-like manner. The lower electrode film 52 is mechanically and electrically connected to the outer contact region 41 within the outer opening 50.

[0232] The main electrode film 53 directly covers the lower electrode film 52. The main electrode film 53 collectively covers the region of the interlayer film 47 where the outer opening 50 is formed, and backfills the outer opening 50.

[0233] The main electrode film 53 has a portion that covers the insulating main surface of the interlayer film 47 with the lower electrode film 52 in between, a portion that covers the wall surface of the outer opening 50 with the lower electrode film 52 in between, and a portion that covers the first main surface 3 with the lower electrode film 52 in between. The main electrode film 53 is electrically connected to the outer contact region 41 within the outer opening 50 via the lower electrode film 52.

[0234] Although the cross-sectional structure is omitted, the aforementioned gate electrode 57 and gate wiring 58 (see Figure 1) also have a laminated structure including a lower electrode film 52 and a main electrode film 53 laminated in this order from the chip 2 side, similar to the source electrode 51 and source wiring 56.

[0235] The concentration gradients of the n-type impurity concentration and the p-type impurity concentration in the impurity region in the chip 2 will be specifically described below.

[0236] The numerical values ​​of impurity concentration, thickness, etc. shown below are examples for explaining the basic configuration of the outer contact region 41, the first outer well region 42 (the first region 12 and the second region 13), and the second semiconductor region 7 (the base region 71 and the high-concentration region 72) based on the concentration gradient, and are not intended to uniquely limit the configuration of the outer contact region 41, the first outer well region 42 (the first region 12 and the second region 13), and the second semiconductor region 7 (the base region 71 and the high-concentration region 72). The impurity concentration, thickness, etc. are adjusted to various values ​​depending on the implantation conditions (dose, implantation temperature, implantation energy, etc.) of the trivalent or pentavalent element. Furthermore, the term "concentration gradient" may be completely replaced with the term "concentration profile."

[0237] Fig. 13A is a graph showing an example of the concentration gradient of p-type impurities in the region along line XIII-XIII shown in Fig. 9. In Fig. 13A, the vertical axis represents the p-type impurity concentration of the outer contact region 41 and the outer well region 40 (first outer well region 42), and the horizontal axis represents the depth in the thickness direction of the second semiconductor region 7, with the upper end (first main surface 3) of the second semiconductor region 7 as the reference (zero point).

[0238] 13A, the outer contact region 41 has a concentration gradient specific to an impurity region formed by random implantation. Fig. 13A shows the concentration gradient of the outer contact region 41 when a predetermined trivalent element (here, aluminum) is introduced into the second semiconductor region 7 in a random direction with an implantation energy of 190 KeV. The random direction is a direction (for example, the vertical direction Z) that is not parallel (almost parallel) to the axial channel of the second semiconductor region 7. The depth (thickness) of the outer contact region 41 is about 0.5 μm, and the dose of the trivalent element is 1×10 １３ cm －２ is.

[0239] The outer contact region 41 has a sudden increase portion 73, a peak portion 74 (peak value P0), and a sudden decrease portion 75 within a range of 0.5 μm.

[0240] The sudden increase portion 73 is a portion where the impurity concentration suddenly increases from the first main surface 3 toward the peak portion 74. The sudden decrease portion 75 is a portion where the impurity concentration suddenly decreases from the peak portion 74 toward the first lower end 42b of the first outer well region 42. For example, the depth position of the peak portion 74 is 0.2 μm or more and 0.3 μm or less. The outer contact region 41 may have the sudden increase portion 73 and the sudden decrease portion 75 in the range of 0.1 μm or more and 0.2 μm or less on the shallower and deeper sides of the peak portion 74, respectively.

[0241] The sudden increase portion 73 has a thickness of 0.1 μm or more and 0.2 μm or less, and has a density change rate of 100% or more within this thickness range.Similarly, the sudden decrease portion 75 has a thickness of 0.1 μm or more and 0.2 μm or less, and has a density change rate of 100% or more within this thickness range.

[0242] The second region 13 of the first outer well region 42 has a concentration gradient specific to an impurity region formed by random implantation. Figure 13A shows the concentration gradient of the second region 13 when a predetermined trivalent element (here, aluminum) is introduced into the second semiconductor region 7 in a random direction with an implantation energy of 500 KeV. The random direction is a direction (for example, the vertical direction Z) that is not parallel (almost parallel) to the axial channel of the second semiconductor region 7. The depth (thickness) of the second region 13 is about 0.5 μm, and the dose of the trivalent element is 1 × 10 １３ cm －２ is.

[0243] The second region 13 has a sudden increase portion 94, a peak portion 95 (peak value P1), and a sudden decrease portion 96 within a range of 0.5 μm.

[0244] The sudden increase portion 94 is a portion where the impurity concentration suddenly increases from the first main surface 3 toward the peak portion 95. The sudden decrease portion 96 is a portion where the impurity concentration suddenly decreases from the peak portion 95 toward the first lower end 42b of the first outer well region 42. For example, the depth position of the peak portion 95 is 0.2 μm or more and 0.3 μm or less from the boundary with the outer contact region 41. The second region 13 may have the sudden increase portion 94 and the sudden decrease portion 96 in the range of 0.1 μm or more and 0.2 μm or less on the shallower and deeper sides of the peak portion 95, respectively.

[0245] The sudden increase portion 94 has a thickness of 0.1 μm or more and 0.2 μm or less, and has a density change rate of 100% or more within this thickness range. Similarly, the sudden decrease portion 96 has a thickness of 0.1 μm or more and 0.2 μm or less, and has a density change rate of 100% or more within this thickness range.

[0246] The first region 12 of the first outer well region 42 has a concentration gradient specific to an impurity region formed by channeling implantation. Fig. 13A shows the concentration gradient of the first region 12 when a predetermined trivalent element (here, aluminum) is introduced into the second semiconductor region 7 parallel or nearly parallel to the axial channel of the second semiconductor region 7 with an implantation energy of 650 KeV. The depth (thickness) of the first region 12 from the boundary 60 is about 2.5 µm, and the dose of the trivalent element is 1 × 10 １３ cm －２ is.

[0247] The p-type impurity concentration of the first region 12 has a concentration gradient from the first upper end 42a side toward the first lower end 42b, including a gradually increasing portion 20, a peak portion 21, a gradual portion 22, and a gradually decreasing portion 23. The gradually increasing portion 20 is a portion that forms the boundary portion 60 of the first region 12, and is a portion where the p-type impurity concentration gradually increases from the first upper end 42a side toward the first lower end 42b side to the peak portion 21 at a relatively steep rate of increase.

[0248] The peak portion 21 is a portion having a peak value P2 (maximum value) of the p-type impurity concentration. The peak portion 21 is also a convex main concentration transition portion including a series of concentration changes (inflection points) where the p-type impurity concentration changes from an increase (increasing trend) to a decrease (decreasing trend). The depth position of the peak portion 21 from the boundary portion 60 is 0.5 μm or more and 1 μm or less.

[0249] The gradual portion 22 is formed in a region closer to the first lower end 42b than the peak portion 21, and is a portion where the impurity concentration gradually decreases at a relatively gradual rate. In other words, the gradual portion 22 is a portion where a constant p-type impurity concentration is maintained within a certain depth range, and forms the main body of the first region 12. The p-type impurity concentration of the gradual portion 22 gradually decreases within a concentration range that is less than the p-type impurity concentration of the peak portion 21.

[0250] The gradual portion 22 is defined as a portion having a concentration decrease rate of 50% or less in a thickness range of at least 1 μm. In this example, the gradual portion 22 has a thickness of 0.7 μm or more and 1.5 μm or less, and has a concentration decrease rate of 50% or less in this thickness range. In this example, the p-type impurity concentration of the gradual portion 22 is 4.5×10 １６ cm －３ 9 x 10 or more １６ cm －３ The concentration range is as follows:

[0251] The gradually decreasing portion 23 is a portion that forms the first lower end 42b of the first outer well region 42. The gradually decreasing portion 23 has a concentration decrease rate that is greater than that of the gradual portion 22, and is a portion where the p-type impurity concentration gradually decreases from the gradual portion 22 toward the first lower end 42b. The concentration decrease rate per unit thickness of the gradually decreasing portion 23 is greater than the concentration decrease rate per unit thickness of the gradual portion 22. The p-type impurity concentration of the gradually decreasing portion 23 is 1×10 １５ cm －３ It is gradually decreasing to.

[0252] 13B is a graph showing an example of the concentration gradient of n-type impurities in a region along line XIII-XIII shown in FIG. 13B shows the concentration gradient of n-type impurities across the first outer well region 42 in the depth direction of the chip 2 from the first main surface 3. In FIG. 13B, the vertical axis represents the n-type impurity concentrations of the outer contact region 41, the outer well region 40 (first outer well region 42), and the second semiconductor region 7, and the horizontal axis represents the depth in the thickness direction of the second semiconductor region 7, with the upper end (first main surface 3) of the second semiconductor region 7 as the reference (zero point).

[0253] 13B , in the depth direction of the second semiconductor region 7, the first outer well region 42 is a p-type impurity region but has a background concentration gradient of n-type impurities. More specifically, the second semiconductor region 7 is replaced with various impurity regions in the target region by ion implantation after epitaxial growth, but the n-type impurity ions added during the epitaxial growth of the second semiconductor region 7 remain at the concentration at the time of growth. This allows the second semiconductor region 7 to provide an n-type background concentration within a range that does not impair the characteristics (electrical behavior) of the various impurity regions. On the other hand, even if only a small amount of n-type or p-type impurity ions are implanted into the second semiconductor region 7, the characteristics of the second semiconductor region 7 are maintained in the region, and the second semiconductor region 7 remains.

[0254] On the other hand, the area below the first outer well region 42 in the depth direction of the second semiconductor region 7 is a region in which the n-type characteristics of the second semiconductor region 7 are maintained, and provides a concentration gradient of the n-type impurity concentration of the second semiconductor region 7.

[0255] 13B includes a high-concentration section 97 and a low-concentration section 98. The n-type impurity concentrations in the high-concentration section 97 and the low-concentration section 98 may be substantially constant in the thickness direction. Of course, the n-type impurity concentrations in the high-concentration section 97 and the low-concentration section 98 may have a concentration gradient that gradually increases and / or gradually decreases in the thickness direction (crystal growth direction) of the chip 2.

[0256] The n-type impurity concentration in the high concentration section 97 is relatively higher than the n-type impurity concentration in the low concentration section 98. For example, when the n-type impurity concentration in the high concentration section 97 is 1×10 １７ cm －３ 1x10 or more １８ cm －３ The n-type impurity concentration in the low concentration section 98 is 1×10 １６ cm －３ 1x10 or more １７ cm －３ It may be the following:

[0257] In this embodiment, the high concentration section 97 is formed within the first outer well region 42, and the low concentration section 98 is formed in part of the first outer well region 42 and outside the first outer well region 42. That is, in the entirety or part of the first outer well region 42 in the depth direction of the second semiconductor region 7, the background concentration of the first outer well region 42 has the impurity concentration in the high concentration section 97. In this embodiment, the background concentration of the first region 12 of the first outer well region 42 has the impurity concentration in the high concentration section 97. Of course, the background concentration of the second region 13 of the first outer well region 42 may also have the impurity concentration in the high concentration section 97.

[0258] Fig. 14 is a graph showing an example of the concentration gradient of n-type impurities in the regions along line XIV-XIV shown in Fig. 9. In Fig. 14, the vertical axis represents the n-type impurity concentration of the source region 11, the high-concentration region 72, and the base region 71, and the horizontal axis represents the depth in the thickness direction of the second semiconductor region 7, with the upper end (first main surface 3) of the second semiconductor region 7 as the reference (zero point).

[0259] 14 , in the depth direction of the second semiconductor region 7, the second semiconductor region 7 has a first concentration gradient 76 based on a high-concentration region 72 in a relatively shallow portion, and a second concentration gradient 77 based on a base region 71 in a portion deeper than the first concentration gradient 76. The second semiconductor region 7 exhibits a two-stage concentration gradient including the first concentration gradient 76 and the second concentration gradient 77. Note that in FIG. 14 , the concentration gradient 78 is a concentration gradient based on the n-type source region 11. The n-type impurity concentrations of the first concentration gradient 76 and the second concentration gradient 77 may be approximately constant in the thickness direction. Of course, the n-type impurity concentrations of the first concentration gradient 76 and the second concentration gradient 77 may have a concentration gradient that gradually increases and / or decreases in the thickness direction (crystal growth direction) of the chip 2.

[0260] For example, when the n-type impurity concentration in the first concentration gradient 76 is 1×10 １７ cm －３ 1x10 or more １８ cm －３ The n-type impurity concentration in the second concentration gradient 77 is 1×10１６ cm －３ 1x10 or more １７ cm －３ It may be the following:

[0261] 13B and 14, in the depth direction of the chip 2, the background concentration gradient (high concentration section 97) in the first outer well region 42 shown in Fig. 13B is equal to the first concentration gradient 76 of the high concentration region 72 shown in Fig. 14. Here, the concentration gradients being equal may be defined as, for example, showing approximately the same concentration profile when the impurity concentration in the depth direction of the chip 2 is analyzed by secondary ion mass spectrometry (SIMS).

[0262] 9, the high concentration region 72 extends along the first major surface 3 across the peripheral boundary 19 to the first outer well region 42, providing an n-type background concentration in the first outer well region 42. For clarity, the high concentration region 72 that provides the background concentration in the first outer well region 42 is shown hatched in FIG.

[0263] Fig. 15 is a graph showing an example of the concentration gradient of n-type impurities in a region along line XV-XV shown in Fig. 10. Fig. 15 shows the concentration gradient of n-type impurities when passing through the side of the first outer well region 42 (a region where the first outer well region 42 is not formed) in the depth direction of the chip 2 from the first main surface 3. In Fig. 15, the vertical axis represents the n-type impurity concentration in the base region 71, and the horizontal axis represents the depth in the thickness direction of the second semiconductor region 7, with the upper end (first main surface 3) of the second semiconductor region 7 as the reference (zero point).

[0264] 15 , in this region, a base region 71 is formed from the first main surface 3 throughout the second semiconductor region 7 in the depth direction of the second semiconductor region 7. Therefore, the second semiconductor region 7 has the second concentration gradient 77 shown in FIG. 14 throughout the entire depth direction. The n-type impurity concentration of the second concentration gradient 77 may be approximately constant in the thickness direction. Of course, the n-type impurity concentration of the second concentration gradient 77 may have a concentration gradient that gradually increases and / or gradually decreases in the thickness direction (crystal growth direction) of the chip 2.

[0265] 13B and 15, in the depth direction of the chip 2, the background concentration gradient (low concentration section 98) in the first outer well region 42 shown in Fig. 13B is equal to the second concentration gradient 77 shown in Fig. 15. In this embodiment, the background concentration of the second region 13 of the first outer well region 42 has a background concentration gradient (low concentration section 98) equal to the second concentration gradient 77.

[0266] Fig. 16 is a graph showing an example of the concentration gradient in the region along line XVI-XVI shown in Fig. 11. In Fig. 16, the vertical axis represents the p-type impurity concentration in the outer well region 40 (second outer well region 43), and the horizontal axis represents the depth in the thickness direction of the second semiconductor region 7, with the upper end (first main surface 3) of the second semiconductor region 7 as the reference (zero point).

[0267] 16, the second outer well region 43 has a concentration gradient specific to an impurity region formed by channeling implantation. Fig. 16 shows the concentration gradient of the second outer well region 43 when a predetermined trivalent element (here, aluminum) is introduced into the second semiconductor region 7 parallel or nearly parallel to the axial channel of the second semiconductor region 7 with an implantation energy of 650 KeV. The depth (thickness) of the second outer well region 43 is about 3 μm, and the dose of the trivalent element is 1×10 １３ cm －２ is.

[0268] The p-type impurity concentration of the second outer well region 43 has a concentration gradient from the second upper end 43a to the second lower end 43b, including a gradually increasing portion 85, a peak portion 86, a gradual portion 87, and a gradually decreasing portion 88. The gradually increasing portion 85 is a portion that forms the second upper end 43a of the second outer well region 43, and is a portion where the p-type impurity concentration gradually increases from the second upper end 43a toward the second lower end 43b to the peak portion 86 at a relatively steep rate of increase.

[0269] The peak portion 86 is a portion having a peak value P4 (maximum value) of the p-type impurity concentration. The peak portion 86 is also a convex main concentration transition portion including a series of concentration changes (inflection points) where the p-type impurity concentration changes from an increase (increasing trend) to a decrease (decreasing trend). The depth position of the peak portion 86 is 0.5 μm or more and 1 μm or less.

[0270] The gradual portion 87 is formed in a region closer to the second lower end 43b than the peak portion 86, and is a portion where the impurity concentration gradually decreases at a relatively gradual rate. In other words, the gradual portion 87 is a portion where a constant p-type impurity concentration is maintained within a certain depth range, and forms the main body of the second outer well region 43. The p-type impurity concentration of the gradual portion 87 gradually decreases within a concentration range that is less than the p-type impurity concentration of the peak portion 86.

[0271] The gradual portion 87 is defined as a portion having a concentration drop rate of 50% or less in a thickness range of at least 1 μm. In this example, the gradual portion 87 has a thickness of 0.7 μm or more and 1.5 μm or less, and has a concentration drop rate of 50% or less in this thickness range. The p-type impurity concentration of the gradual portion 87 is 4.5×10 １６ cm －３ 9 x 10 or more １６ cm －３ The concentration range is as follows:

[0272] The gradually decreasing portion 88 is a portion that forms the second lower end 43b of the second outer well region 43. The gradually decreasing portion 88 has a concentration decrease rate that is greater than the concentration decrease rate in the gradual portion 87, and is a portion where the p-type impurity concentration gradually decreases from the gradual portion 87 toward the second lower end 43b. The concentration decrease rate per unit thickness of the gradually decreasing portion 88 is greater than the concentration decrease rate per unit thickness of the gradual portion 87. The p-type impurity concentration of the gradually decreasing portion 88 decreases from the gradual portion 87 by 1×10 １５ cm －３ It is gradually decreasing to.

[0273] As described above, the semiconductor device 1A has a two-layer structure including a lower layer made of a relatively low-concentration first region 12 and an upper layer made of a relatively higher-concentration second region 13 than the first region 12, as shown in FIG. This allows the depletion layer to extend along the first main surface 3 to the first side 42d (outer end) of the first outer well region 42. As a result, the electric field with respect to the terminal gate structure 15A and the bottom of the gate structure 15 near the terminal gate structure 15A can be alleviated, thereby suppressing a decrease in breakdown voltage (breakdown voltage) due to electric field concentration. In other words, a decrease in breakdown voltage originating from the peripheral boundary 19 between the active region 8 and the peripheral region 9 can be suppressed.

[0274] 9 and 13B , the high concentration region 72 extends along the first main surface 3 across the outer boundary 19 to the first outer well region 42, providing an n-type background concentration to the first outer well region 42. By selectively increasing the n-type background concentration of the first outer well region 42 in this manner, the dielectric breakdown field value of the first outer well region 42 can be increased. As a result, the avalanche resistance can be improved.

[0275] The p-type impurity concentration of the first outer well region 42 formed by channeling implantation has a gradually increasing portion 20, a peak portion 21, a gradual portion 22, and a gradually decreasing portion 23. The gradual portion 22 occupies a thickness range of at least one-quarter of the first outer well region 42 and is located within the second semiconductor region 7. Specifically, the proportion of the gradual portion 22 in the first outer well region 42 is at least one-third. The proportion of the gradual portion 22 in the first outer well region 42 is typically at most one-half (less than one-half). The proportion of the gradual portion 22 in the first outer well region 42 may be at least one-half.

[0276] On the other hand, if the outer contact region 41 is formed by random implantation, it is difficult to realize a concentration gradient similar to the concentration gradient having the gradually increasing portion 20, the peak portion 21, the gradual portion 22, and the gradually decreasing portion 23 described above.

[0277] Therefore, when forming the first outer well region 42 shown in FIG. 9 by the random implantation method, it is necessary to employ a multi-stage random implantation method. In the multi-stage random implantation method, a process of introducing a trivalent element into the second semiconductor region 7 at different depths using multiple implantation energies is performed. For example, the trivalent element is introduced into the second semiconductor region 7 using different implantation energies, such as three stages, five stages, and seven stages. In this process, the trivalent element can be introduced to the desired depth, but the thickness of the region into which the trivalent element can be introduced is narrow. Therefore, to implant the element deeper, the number of steps in the random implantation method must be increased, complicating the manufacturing process. As a result, the design of the first outer well region 42 becomes complicated, and the increased number of ion implantation steps also increases the burden on the device.

[0278] In contrast, with the channeling implantation method, a first outer well region 42 having a relatively thick gentle portion 22 can be formed by a single ion implantation process. The first outer well region 42 for improving the breakdown voltage can be formed with fewer steps than when the random implantation method is used. As a result, the design of the first outer well region 42 can be simplified, and the burden on the device can be reduced.

[0279] Similarly, the p-type impurity concentration of the second outer well region 43 also has a gradually increasing portion 85, a peak portion 86, a gradual portion 87, and a gradually decreasing portion 88. Therefore, the design of the second outer well region 43 can be simplified, and the load on the device can also be reduced.

[0280] 17 to 20 are cross-sectional views showing outer well regions 40 according to the second to fifth embodiments. The semiconductor device 1A may include at least one of the outer well regions 40 according to the first to fifth embodiments. The semiconductor device 1A may simultaneously include at least two of the outer well regions 40 according to the first to fifth embodiments in the same cross-sectional region or different cross-sectional regions.

[0281] 17 (second embodiment), the first lower end 42b of the first outer well region 42 of the semiconductor device 1A may be located closer to the bottom of the second semiconductor region 7 with respect to the depth position of a boundary 62 between the high-concentration region 72 and the base region 71. The first lower end 42b may be a portion of the first outer well region 42 that protrudes further toward the bottom of the second semiconductor region 7 than the boundary 62 between the high-concentration region 72 and the base region 71 in the thickness direction of the second semiconductor region 7. As a result, the inner end 12b of the first region 12 may cross the boundary 62 between the high-concentration region 72 and the base region 71 in the thickness direction of the second semiconductor region 7 and be in contact with both side portions of the high-concentration region 72 and the base region 71.

[0282] 18 (third embodiment), the first lower end 42b of the first outer well region 42 of the semiconductor device 1A may be located closer to the first main surface 3 than the depth position of the boundary 62 between the high-concentration region 72 and the base region 71. The first lower end 42b may be spaced apart from the boundary 62 between the high-concentration region 72 and the base region 71 toward the first main surface 3 in the thickness direction of the second semiconductor region 7. As a result, the high-concentration region 72 may have an extension 14 that extends across the outer periphery boundary 19 into the outer periphery region 9 and covers the first lower end 42b of the first outer well region 42 from the second main surface 4 side. The extension 14 contacts the first lower end 42b of the first outer well region 42 along the first main surface 3, forming a flat boundary along the first main surface 3.

[0283] 19 (fourth embodiment), the semiconductor device 1A may include a first outer well region 42 having a first side portion 42d extending vertically from a first upper end portion 42a to a first lower end portion 42b. That is, the first side portion 42d does not have to be inclined with respect to the first main surface 3.

[0284] 20 (fifth embodiment), the semiconductor device 1A may include a second outer well region 43 having a second side portion 43 d extending vertically from a second upper end portion 43 a toward a second lower end portion 43 b. That is, the second side portion 43 d does not need to be inclined with respect to the first main surface 3.

[0285] Fig. 21 is a graph showing the concentration gradient of the outer well region 40 according to the second embodiment. In Fig. 21, the vertical axis represents the p-type impurity concentration of the outer well region 40 (first outer well region 42 and second outer well region 43), and the horizontal axis represents the depth in the thickness direction of the second semiconductor region 7, with the upper end (first main surface 3) of the second semiconductor region 7 as the reference (zero point).

[0286] 21 is a graph showing the concentration gradient of the outer well region 40 formed by random implantation. This graph shows the concentration gradient of the outer well region 40 when a predetermined trivalent element (aluminum in this case) is introduced into the second semiconductor region 7 in a random direction with implantation energies of 190 KeV, 380 KeV, 650 KeV, 960 KeV, or 2000 KeV. The random direction is a direction (for example, the vertical direction Z) that is not parallel (or substantially parallel) to the axial channel of the second semiconductor region 7.

[0287] That is, the outer well region 40 may be formed to a predetermined depth (for example, a depth deeper than the gate well region 25) by the multi-stage random implantation method. In this case, it becomes difficult to directly enjoy the effects of simplifying the design of the first outer well region 42 and reducing the load on the device.

[0288] However, as shown in FIG. 9, if the first outer well region 42 has a two-layer structure including the first region 12 and the second region 13, even if the injection method is changed, the electric field with respect to the terminal gate structure 15A and the bottom of the gate structure 15 near the terminal gate structure 15A can be alleviated, and a decrease in breakdown voltage due to electric field concentration can be suppressed.

[0289] Fig. 22 is a plan view showing an example of the layout of a chip of a semiconductor device 1B according to a second embodiment of the present disclosure. Fig. 23 is an enlarged plan view showing a main portion of the first main surface 3 shown in Fig. 22. Fig. 24 is an enlarged plan view showing a main portion of the first main surface 3 shown in Fig. 22. Fig. 25 is a cross-sectional view taken along line XXV-XXV shown in Fig. 23. Fig. 26 is a cross-sectional view taken along line XXVI-XXVI shown in Fig. 23. Fig. 27 is a cross-sectional view taken along line XXVII-XXVII shown in Fig. 24.

[0290] 22 to 27, semiconductor device 1B has a configuration in which a configuration of a plurality of source structures 90 and a configuration of a plurality of isolation structures 30 are introduced into semiconductor device 1B.

[0291] The semiconductor device 1B includes a plurality of trench-type (trench electrode-type) source structures 90 formed in an inner portion of the first main surface 3. The source structures 90 may be referred to as "first source structures," "source structures," "second trench structures," etc. A source potential is applied to the plurality of source structures 90.

[0292] The plurality of source structures 90 are formed in the inner part of the first main surface 3 at intervals from the periphery (first to fourth side surfaces 5A to 5D) of the first main surface 3, and are not formed in the outer peripheral region 9. The plurality of source structures 90 are arranged at intervals in the first direction X (= m-axis direction) in plan view, and each extends in a strip shape in the second direction Y (= a-axis direction).

[0293] The source structures 90 are arranged in regions between the gate structures 15 at intervals in the first direction X from the gate structures 15, and face the gate structures 15 in the first direction X. That is, the source structures 90 are arranged alternately with the gate structures 15 in the first direction X, and extend in a strip-like manner in the second direction Y. The source structures 90 are arranged in a strip-like manner extending in the second direction Y.

[0294] The extension direction of the source structures 90 coincides with the off-direction of the SiC single crystal. With respect to the second direction Y, both ends of the source structures 90 may be located in a region between the periphery of the body region 10 and the periphery of the source region 11. The source structures 90 may be arranged at intervals in the second direction Y according to the extension direction of the gate structures 15, and may each extend in a strip shape in the first direction X.

[0295] The plurality of source structures 90 penetrate the body region 10 and the source region 11 to reach the second semiconductor region 7. The plurality of source structures 90 are formed at intervals from the bottom of the second semiconductor region 7 toward the first main surface 3, and face the first semiconductor region 6 with a part of the second semiconductor region 7 in between.

[0296] The multiple source structures 90 may be formed at intervals from a depth position of an intermediate portion of the second semiconductor region 7 toward the first main surface 3, or may be located on the bottom side of the second semiconductor region 7 with respect to the depth position of the intermediate portion of the second semiconductor region 7. The multiple source structures 90 are formed substantially perpendicular to the first main surface 3. The multiple source structures 90 may be formed in a shape that tapers toward the bottom of the second semiconductor region 7.

[0297] The side walls of the plurality of source structures 90 are each formed by the m-plane ((1-100) plane) of the SiC single crystal. The side walls of the plurality of source structures 90 may be formed by the a-plane ((11-20) plane) of the SiC single crystal depending on the extension direction of the source structures 90. The bottom walls of the plurality of source structures 90 are formed by the c-plane (Si-plane) of the SiC single crystal. It is preferable that the bottom walls of the plurality of source structures 90 extend substantially flat in the horizontal direction. The bottom walls of the plurality of source structures 90 may be curved in an arc shape toward the second main surface 4.

[0298] The inclination angle (absolute value) of the sidewall of the source structure 90 relative to the vertical line may be 85° or more and 95° or less. The inclination angle may have a value belonging to at least one of the ranges of 85° or more and 87.5° or less, 87.5° or more and 90° or less, 90° or more and 92.5° or less, and 92.5° or more and 95° or less. The inclination angle is preferably 87° or more and 93° or less.

[0299] The source structure 90 has a width that is approximately equal to the width of the gate structure 15. The width of the source structure 90 may be greater than the width of the gate structure 15 or may be less than the width of the gate structure 15.

[0300] The width of the source structure 90 may be 0.1 μm to 2 μm, and may have a value belonging to at least one of the ranges of 0.1 μm to 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 0.75 μm, 0.75 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, and 1.75 μm to 2 μm.

[0301] The source structure 90 has a depth approximately equal to the depth of the gate structure 15. The depth of the source structure 90 is measured from the first main surface 3. The depth of the source structure 90 may be greater than the depth of the gate structure 15 or may be less than the depth of the gate structure 15.

[0302] The ratio (depth ratio) of the depth of the source structure 90 to the depth of the gate structure 15 may be 0.8 to 1.2. The depth ratio may have a value belonging to at least one of the ranges of 0.8 to 0.85, 0.85 to 0.9, 0.9 to 0.95, 0.95 to 1, 1 to 1.05, 1.05 to 1.1, 1.1 to 1.15, and 1.15 to 1.2. The depth ratio is preferably 0.95 to 1.05.

[0303] The depth of the source structure 90 may be 0.1 μm or more and 3 μm or less. The depth of the source structure 90 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.5 μm or less, 0.5 μm or more and 1 μm or less, 1 μm or more and 1.5 μm or less, 1.5 μm or more and 2 μm or less, 2 μm or more and 2.5 μm or less, and 2.5 μm or more and 3 μm or less. The depth of the source structure 90 is preferably 0.5 μm or more and 1.5 μm or less.

[0304] The source structure 90 may have an aspect ratio of 1 to 3, inclusive. The aspect ratio of the source structure 90 is the ratio of the depth of the source structure 90 to the width of the source structure 90. The aspect ratio may have a value belonging to at least one of the following ranges: 1 to 1.25, 1.25 to 1.5, 1.5 to 1.75, 1.75 to 2, 2 to 2.25, 2.25 to 2.5, 2.5 to 2.75, and 2.75 to 3, inclusive. Preferably, the aspect ratio is 1.5 to 2.5, inclusive.

[0305] The pitch between the central portions of the source structures 90 and the gate structures 15 may be 0.1 μm to 2.5 μm. The pitch may have a value belonging to at least one of the ranges of 0.1 μm to 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, 1.75 μm to 2 μm, 2 μm to 2.25 μm, and 2.25 μm to 2.5 μm.

[0306] Each of the plurality of source structures 90 includes a second trench 91, a second insulating film 92, and a second buried electrode 93. The second trench 91 is formed in the first main surface 3 and defines the wall surfaces (sidewalls and bottom wall) of the source structure 90.

[0307] The second insulating film 92 may include at least one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. The second insulating film 92 preferably includes the same insulating material as the insulating material of the first insulating film 17. In this embodiment, the second insulating film 92 has a single-layer structure made of a silicon oxide film. It is particularly preferable that the second insulating film 92 includes a silicon oxide film made of an oxide of the chip 2.

[0308] The second insulating film 92 covers the wall surface of the second trench 91. The second insulating film 92 includes a first film portion and a second film portion. The first film portion covers the side wall of the second trench 91 in a film-like manner. The second film portion covers the bottom wall of the second trench 91 in a film-like manner and is continuous with the first film portion.

[0309] The second film portion has a thickness greater than that of the first film portion. The thickness of the second film portion may be approximately equal to the thickness of the first film portion. The thickness of the first film portion of the second insulating film 92 may be approximately equal to the thickness of the first film portion of the first insulating film 17. The thickness of the second film portion of the second insulating film 92 may be approximately equal to the thickness of the second film portion of the first insulating film 17.

[0310] The second insulating film 92 may have a thickness of 10 nm to 150 nm, and may have a thickness in at least one range of 10 nm to 25 nm, 25 nm to 50 nm, 50 nm to 75 nm, 75 nm to 100 nm, 100 nm to 125 nm, and 125 nm to 150 nm.

[0311] The second buried electrode 93 is buried in the second trench 91 with the second insulating film 92 sandwiched therebetween. The second buried electrode 93 may contain either or both of p-type conductive polysilicon and n-type conductive polysilicon. The second buried electrode 93 preferably contains the same type of conductive material as the conductive material of the first buried electrode 18. The second buried electrode 93 faces the second semiconductor region 7, the body region 10, and the source region 11 with the second insulating film 92 sandwiched therebetween.

[0312] The second buried electrode 93 has an electrode surface exposed from the second trench 91. The electrode surface is located closer to the bottom wall of the second trench 91 with respect to the height position of the first main surface 3. The electrode surface is located closer to the first main surface 3 with respect to the depth position of the bottom of the source region 11. The electrode surface has a recess in an inner portion that tapers toward the bottom wall of the second trench 91.

[0313] The semiconductor device 1B includes a plurality of source well regions 26 formed in regions below the plurality of source structures 90 within the chip 2 (second semiconductor region 7) of the active region 8. The source well regions 26 may also be referred to as "second well regions" or the like. A source potential is applied to the source well regions 26.

[0314] The source well region 26 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the source well region 26 may be higher than the p-type impurity concentration of the body region 10 or may be lower than the p-type impurity concentration of the body region 10.

[0315] The p-type impurity concentration of the source well region 26 may be approximately equal to the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the source well region 26 may be higher than the p-type impurity concentration of the gate well region 25, or may be lower than the p-type impurity concentration of the gate well region 25. The p-type impurity (trivalent element) of the source well region 26 is preferably aluminum.

[0316] The multiple source well regions 26 are formed in the second semiconductor region 7 in regions below (specifically, directly below) the multiple source structures 90, spaced apart in the horizontal direction (first direction X) from the multiple gate well regions 25. The multiple source well regions 26 are formed in the thickness range between the bottom of the second semiconductor region 7 and the bottom walls of the multiple source structures 90, and overlap the multiple source structures 90 in a one-to-one correspondence in the thickness direction.

[0317] The multiple source well regions 26 each extend in a strip shape in the second direction Y in plan view, following the extension direction of the corresponding source structure 90. In other words, the multiple source well regions 26 are arranged in stripes extending in the second direction Y in plan view.

[0318] The extension direction of the multiple source well regions 26 coincides with the off-direction of the SiC single crystal. The multiple source well regions 26 may extend in the first direction X according to the extension direction of the multiple source structures 90. In this case, the multiple source well regions 26 intersect (specifically, are perpendicular to) the off-direction.

[0319] The multiple source well regions 26 are formed at intervals inward from the periphery of the active region 8. In the second direction Y, both ends of the multiple source well regions 26 may be located inward of the multiple source structures 90 with respect to both ends of the multiple source structures 90, or may be located closer to the periphery of the active region 8 with respect to both ends of the multiple source structures 90.

[0320] The plurality of source well regions 26 are formed at intervals from the bottom of the second semiconductor region 7 toward the bottom wall sides of the plurality of source structures 90, and face the first semiconductor region 6 across a part of the second semiconductor region 7. The plurality of source well regions 26 each have an upper end located on the bottom wall side of the corresponding source structure 90, and a bottom located on the bottom side of the second semiconductor region 7.

[0321] The upper ends of the plurality of source well regions 26 may be connected to the bottom walls of the corresponding source structures 90. The upper ends of the plurality of source well regions 26 may extend along the sidewalls of the corresponding source structures 90 and be connected to the body region 10. The upper ends of the plurality of source well regions 26 may be formed at intervals from the bottom walls of the corresponding source structures 90 toward the bottom of the second semiconductor region 7.

[0322] The bottoms of the multiple source well regions 26 may be located on the bottom wall side of the multiple source structures 90 relative to the intermediate portion of the second semiconductor region 7, or may be located on the bottom side of the second semiconductor region 7 (the side of the second main surface 4) relative to the intermediate portion of the second semiconductor region 7.

[0323] Each of the plurality of source well regions 26 has a bulging portion 26 a. The bulging portion 26 a extends in an arc shape horizontally from a region directly below the corresponding source structure 90 to both sides of the corresponding source structure 90. Each of the plurality of source well regions 26 is formed in a tapered shape from the bulging portion 26 a to the bottom.

[0324] The source well region 26 may have a width approximately equal to the width of the gate well region 25. The width of the source well region 26 may be greater than the width of the gate well region 25 or less than the width of the gate well region 25. The width of the source well region 26 may be greater than the width of the source structure 90 or less than the width of the source structure 90.

[0325] The width of the source well region 26 may be 0.1 μm or more and 2 μm or less. The width of the source well region 26 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.25 μm or less, 0.25 μm or more and 0.5 μm or less, 0.5 μm or more and 0.75 μm or less, 0.75 μm or more and 1 μm or less, 1 μm or more and 1.25 μm or less, 1.25 μm or more and 1.5 μm or less, 1.5 μm or more and 1.75 μm or less, and 1.75 μm or more and 2 μm or less.

[0326] The source well region 26 may have a depth approximately equal to that of the gate well region 25. That is, the bottom of the source well region 26 may be located at a depth approximately equal to that of the bottom of the gate well region 25. The depth of the source well region 26 is the depth of the source well region 26 when referenced to the bottom wall of the source structure 90. The depth of the source well region 26 may be greater than or less than the depth of the gate well region 25.

[0327] The depth of the source well region 26 may be greater than 0 μm and less than or equal to 5 μm. The depth of the source well region 26 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than or equal to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, 3.5 μm to 4 μm, 4 μm to 4.5 μm, and 4.5 μm to 5 μm.

[0328] The source well regions 26 may have an aspect ratio greater than 0 and less than or equal to 2. The aspect ratio of the source well regions 26 is the ratio of the depth of the source well regions 26 to the width of the source well regions 26.

[0329] The aspect ratio may have a value belonging to at least one of the ranges of greater than 0 and less than or equal to 0.25, 0.25 or more and less than or equal to 0.5, 0.5 or more and less than or equal to 0.75, 0.75 or more and less than or equal to 1, 1 or more and less than or equal to 1.25, 1.25 or more and less than or equal to 1.5, 1.5 or more and less than or equal to 1.75, and 1.75 or more and less than or equal to 2.

[0330] The pitch between the centers of the source well regions 26 and the gate well regions 25 (the pitch of the source well regions 26) is approximately equal to the pitch of the source structures 90 and the gate structures 15. The pitch of the source well regions 26 may be 0.1 μm or more and 2.5 μm or less.

[0331] The pitch of the source well regions 26 may have a value belonging to at least one of the ranges of 0.1 μm to 0.25 μm, 0.25 μm to 0.5 μm, 0.5 μm to 1 μm, 1 μm to 1.25 μm, 1.25 μm to 1.5 μm, 1.5 μm to 1.75 μm, 1.75 μm to 2 μm, 2 μm to 2.25 μm, and 2.25 μm to 2.5 μm.

[0332] The source well region 26 forms a pn junction with the second semiconductor region 7. The source well region 26 spreads a depletion layer into the second semiconductor region 7 when a reverse bias voltage is applied. The depletion layer originating from the source well region 26 spreads in the horizontal and thickness directions, alleviating the electric field with respect to the active region 8 (source structure 90). The depletion layer originating from the source well region 26 merges with the depletion layer originating from the gate well region 25.

[0333] The semiconductor device 1B includes a plurality of source contact regions 28 formed in the chip 2 (second semiconductor region 7). The source contact regions 28 may also be referred to as "second contact regions," etc. A source potential is applied to the source contact regions 28.

[0334] The source contact region 28 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the source contact region 28 is higher than the p-type impurity concentration of the body region 10.

[0335] The p-type impurity concentration of the source contact region 28 is higher than the p-type impurity concentration of the source well region 26. The p-type impurity concentration of the source contact region 28 may be approximately equal to the p-type impurity concentration of the gate contact region 27. The p-type impurity concentration of the source contact region 28 may be higher than the p-type impurity concentration of the gate contact region 27 or may be lower than the p-type impurity concentration of the gate contact region 27.

[0336] The source contact regions 28 are formed in regions along the source structures 90, spaced apart from the gate structures 15. The source contact regions 28 have a planar layout that differs from the planar layout of the gate contact regions 27. In this embodiment, the source contact regions 28 are formed in a one-to-one correspondence with the source structures 90.

[0337] The source contact regions 28 extend in a strip shape in the second direction Y in accordance with the extension direction of the corresponding source structures 90. In other words, the source contact regions 28 are formed in a stripe shape extending along the source structures 90 in a plan view.

[0338] The source contact regions 28 have lengths in the second direction Y that are greater than the lengths of the gate contact regions 27 and cross the gate contact regions 27 in the second direction Y. The source contact regions 28 may have lengths in the second direction Y that are greater than the lengths of the source structures 90 or may have lengths that are less than the lengths of the source structures 90.

[0339] The plurality of source contact regions 28 preferably have a total planar area greater than the total planar area of ​​the plurality of gate contact regions 27. The total planar area of ​​the plurality of source contact regions 28 may be greater than the channel area or less than the channel area.

[0340] The source contact regions 28 may be formed in a one-to-many correspondence with the source structures 90, similar to the gate contact regions 27. In this case, with respect to one and the other source structures 90, the gate contact regions 27 along one source structure 90 may face the source contact regions 28 along the other source structure 90 in the first direction X in plan view.

[0341] That is, the multiple source contact regions 28 may be generally arranged in a matrix with gaps in the first direction X and the second direction Y in a plan view. One of the multiple source contact regions 28 may face a region between the other multiple source contact regions 28 in the first direction X in a plan view. That is, the multiple source contact regions 28 may be generally arranged in a staggered pattern with gaps in the first direction X and the second direction Y in a plan view.

[0342] The plurality of source contact regions 28 are respectively interposed in regions between the bottom wall of the corresponding source structure 90 and the bottom of the corresponding source well region 26. The plurality of source contact regions 28 are respectively connected to the bottom wall of the corresponding source structure 90 and the corresponding source well region 26.

[0343] The plurality of source contact regions 28 increase the p-type impurity concentration at the upper end of the corresponding source well region 26. The plurality of source contact regions 28 extend from the region directly below the source structure 90 to both sides of the source structure 90 and have extensions that extend along the sidewalls of the source structure 90.

[0344] The thickness in the horizontal direction (first direction X) of the portion (extension) of the source contact region 28 along the side wall of the source structure 90 may be less than the thickness in the vertical direction Z of the portion of the source contact region 28 along the bottom wall of the source structure 90.

[0345] The extension of the source contact region 28 is electrically connected to the body region 10 in the surface layer portion of the first main surface 3, and electrically connects the corresponding source well region 26 to the body region 10. This prevents the source well region 26 from being electrically floating, and improves the electrical response characteristics of the source well region 26.

[0346] The source contact region 28 has an upper end exposed from the first main surface 3. In this embodiment, the upper end of the source contact region 28 is exposed from the sidewall of the second trench 91 at the opening end of the second trench 91. The upper end of the source contact region 28 may extend horizontally in the surface portion of the body region 10.

[0347] The upper end of the source contact region 28 is electrically connected to the upper end of the adjacent gate contact regions 27 in the body region 10. In this embodiment, the upper end of the source contact region 28 is integrally formed with the upper end of the gate contact region 27.

[0348] The semiconductor device 1B includes one or more (in this embodiment, multiple) trench-type (trench electrode-type) isolation structures 30 formed on the first main surface 3 in the active region 8. The isolation structures 30 may also be referred to as "trench structures," "third trench structures," "dummy structures," etc.

[0349] The number of isolation structures 30 is arbitrary. The number of isolation structures 30 may be 1 or more and 15 or less. The number of isolation structures 30 may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. The number of isolation structures 30 is typically 1 or more and 10 or less. In this embodiment, the semiconductor device 1B includes five isolation structures 30, as an example.

[0350] At least one or all of the plurality of isolation structures 30 may be formed in an electrically floating state. A source potential may be applied to at least one or all of the plurality of isolation structures 30. The plurality of isolation structures 30 may include one or more isolation structures 30 formed in an electrically floating state and one or more isolation structures 30 to which a source potential is applied.

[0351] The plurality of isolation structures 30 are formed in the inner part of the first main surface 3 at intervals from the periphery (first to fourth side surfaces 5A to 5D) of the first main surface 3. The plurality of isolation structures 30 define an active region 8 on the inner side of the first main surface 3, and define an outer periphery region 9 on the peripheral side of the first main surface 3. The active region 8 is located inward of the outermost isolation structure 30A (terminal isolation structure 30A), and the outer periphery region 9 is located outward of the terminal isolation structure 30A.

[0352] The plurality of isolation structures 30 are arranged on the periphery of the active region 8 at intervals from the plurality of gate structures 15 and the plurality of source structures 90. The plurality of isolation structures 30 are arranged at intervals from one another and are adjacent to one another in the horizontal direction with part of the chip 2 sandwiched between them. The plurality of isolation structures 30 each extend in a strip shape along the periphery of the first main surface 3. The plurality of isolation structures 30 have a portion extending in the first direction X and a portion extending in the second direction Y.

[0353] That is, the plurality of isolation structures 30 have portions extending in the extension direction (second direction Y) of the plurality of gate structures 15 (plurality of source structures 90) and portions extending in a direction (first direction X) intersecting the extension direction of the plurality of gate structures 15 (plurality of source structures 90). The plurality of isolation structures 30 may be formed in the shape of a polygonal ring (quadrilateral ring) that collectively surrounds the plurality of gate structures 15 and the plurality of source structures 90 in a plan view.

[0354] The plurality of isolation structures 30 are formed in a region outside the source region 11 and penetrate only the body region 10. The plurality of isolation structures 30 may also penetrate the source region 11. The plurality of isolation structures 30 are formed at intervals from the bottom of the second semiconductor region 7 toward the first main surface 3, and face the first semiconductor region 6 with part of the second semiconductor region 7 in between.

[0355] The plurality of isolation structures 30 may be formed at intervals from a depth position of an intermediate portion of the second semiconductor region 7 toward the first main surface 3, or may be located on the bottom side of the second semiconductor region 7 with respect to the depth position of the intermediate portion of the second semiconductor region 7. The plurality of isolation structures 30 are formed substantially perpendicular to the first main surface 3. The plurality of isolation structures 30 may be formed in a shape tapering toward the bottom of the second semiconductor region 7.

[0356] The side walls of the plurality of isolation structures 30 are formed by the m-plane ((1-100) plane) of the SiC single crystal and the a-plane ((11-20) plane) of the SiC single crystal. The bottom walls of the plurality of isolation structures 30 are formed by the c-plane (Si-plane) of the SiC single crystal. The bottom walls of the plurality of isolation structures 30 preferably extend substantially flat in the horizontal direction. The bottom walls of the plurality of isolation structures 30 may be curved in an arc shape toward the second main surface 4.

[0357] The inclination angle (absolute value) of the sidewall of the isolation structure 30 relative to the vertical line may be 85° or more and 95° or less. The inclination angle may have a value belonging to at least one of the ranges of 85° or more and 87.5° or less, 87.5° or more and 90° or less, 90° or more and 92.5° or less, and 92.5° or more and 95° or less. The inclination angle is preferably 87° or more and 93° or less.

[0358] The isolation structure 30 may have a width that is approximately equal to the width of the gate structure 15. The width of the isolation structure 30 may be greater than or less than the width of the gate structure 15. The width of the isolation structure 30 may be approximately equal to the width of the source structure 90. The width of the isolation structure 30 may be greater than or less than the width of the source structure 90.

[0359] The width of the isolation structure 30 may be 0.1 μm or more and 2 μm or less. The width of the isolation structure 30 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.25 μm or less, 0.25 μm or more and 0.5 μm or less, 0.5 μm or more and 0.75 μm or less, 0.75 μm or more and 1 μm or less, 1 μm or more and 1.25 μm or less, 1.25 μm or more and 1.5 μm or less, 1.5 μm or more and 1.75 μm or less, and 1.75 μm or more and 2 μm or less.

[0360] The isolation structure 30 may have a depth equal to or greater than the depth of the gate structure 15. The depth of the isolation structure 30 is measured from the first main surface 3. The depth of the isolation structure 30 may be greater than the depth of the gate structure 15 or may be less than the depth of the gate structure 15. In this embodiment, the depth of the isolation structure 30 is approximately equal to the depth of the gate structure 15.

[0361] The isolation structures 30 may have a depth equal to or greater than the depth of the source structures 90. The depth of the isolation structures 30 may be greater than or less than the depth of the source structures 90. In this embodiment, the depth of the isolation structures 30 is approximately equal to the depth of the source structures 90.

[0362] The ratio (depth ratio) of the depth of the isolation structure 30 to the depth of the gate structure 15 (source structure 90) may be 0.8 to 1.2. The depth ratio may have a value belonging to at least one of the following ranges: 0.8 to 0.85, 0.85 to 0.9, 0.9 to 0.95, 0.95 to 1, 1 to 1.05, 1.05 to 1.1, 1.1 to 1.15, and 1.15 to 1.2. The depth ratio is preferably 0.95 to 1.05.

[0363] The depth of the isolation structure 30 may be 0.1 μm or more and 3 μm or less. The depth of the isolation structure 30 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.5 μm or less, 0.5 μm or more and 1 μm or less, 1 μm or more and 1.5 μm or less, 1.5 μm or more and 2 μm or less, 2 μm or more and 2.5 μm or less, and 2.5 μm or more and 3 μm or less. The depth of the isolation structure 30 is preferably 0.5 μm or more and 1.5 μm or less.

[0364] The isolation structure 30 may have an aspect ratio of 1 to 3. The aspect ratio of the isolation structure 30 is the ratio of the depth of the isolation structure 30 to the width of the isolation structure 30. The aspect ratio may have a value belonging to at least one of the ranges of 1 to 1.25, 1.25 to 1.5, 1.5 to 1.75, 1.75 to 2, 2 to 2.25, 2.25 to 2.5, 2.5 to 2.75, and 2.75 to 3. The aspect ratio is preferably 1.5 to 2.5.

[0365] The pitch of the centers of the isolation structures 30 (the pitch of the isolation structures 30) is preferably less than the pitch of the gate structures 15 and the source structures 90. The pitch of the isolation structures 30 may be greater than the pitch of the gate structures 15 and the source structures 90.

[0366] The pitch of the isolation structures 30 may be 0.1 μm or more and 2.5 μm or less. The pitch of the isolation structures 30 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.25 μm or less, 0.25 μm or more and 0.5 μm or less, 0.5 μm or more and 1 μm or less, 1 μm or more and 1.25 μm or less, 1.25 μm or more and 1.5 μm or less, 1.5 μm or more and 1.75 μm or less, 1.75 μm or more and 2 μm or less, 2 μm or more and 2.25 μm or less, and 2.25 μm or more and 2.5 μm or less.

[0367] Each of the multiple isolation structures 30 includes a third trench 31, a third insulating film 32, and a third buried electrode 33. The third trench 31 is formed in the first main surface 3 and defines the wall surfaces (sidewalls and bottom wall) of the isolation structure 30. The third trench 31 is a boundary trench that forms the peripheral boundary portion 19, which is the boundary portion between the active region 8 and the peripheral region 9. The terminal isolation structure 30A includes a terminal third trench 31A, a terminal third insulating film 32A, and a terminal third buried electrode 33A. Of the multiple third trenches 31, the terminal third trench 31A may be a boundary trench.

[0368] The third insulating film 32 may include at least one of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. The third insulating film 32 preferably includes the same insulating material as the insulating material of the first insulating film 17 (second insulating film 92). In this embodiment, the third insulating film 32 has a single-layer structure made of a silicon oxide film. It is particularly preferable that the third insulating film 32 includes a silicon oxide film made of an oxide of the chip 2.

[0369] The third insulating film 32 covers the wall surface of the third trench 31. The third insulating film 32 includes a first film portion and a second film portion. The first film portion covers the side wall of the third trench 31 in a film-like manner. The second film portion covers the bottom wall of the third trench 31 in a film-like manner and is continuous with the first film portion.

[0370] The second film portion has a thickness greater than that of the first film portion. The thickness of the second film portion may be approximately equal to the thickness of the first film portion. The thickness of the first film portion of the third insulating film 32 may be approximately equal to the thickness of the first film portion of the first insulating film 17. The thickness of the second film portion of the third insulating film 32 may be approximately equal to the thickness of the second film portion of the first insulating film 17.

[0371] The third insulating film 32 may have a thickness of 10 nm to 150 nm, and may have a thickness in at least one range of 10 nm to 25 nm, 25 nm to 50 nm, 50 nm to 75 nm, 75 nm to 100 nm, 100 nm to 125 nm, and 125 nm to 150 nm.

[0372] The third buried electrode 33 is buried in the third trench 31 with the third insulating film 32 sandwiched therebetween. The third buried electrode 33 may include either or both of p-type conductive polysilicon and n-type conductive polysilicon. The third buried electrode 33 preferably includes the same type of conductive material as the conductive material of the first buried electrode 18. The third buried electrode 33 faces the second semiconductor region 7 and the body region 10 with the third insulating film 32 sandwiched therebetween. The third buried electrode 33 may have a portion facing the source region 11.

[0373] The third buried electrode 33 has an electrode surface exposed from the third trench 31. The electrode surface is located closer to the bottom wall of the third trench 31 with respect to the height position of the first main surface 3. The electrode surface is located closer to the first main surface 3 with respect to the depth position of the bottom of the source region 11. The electrode surface has a recess in an inner portion that tapers toward the bottom wall of the third trench 31.

[0374] The semiconductor device 1B includes one or more (four in this embodiment) isolation well regions 35 formed in the chip 2 (second semiconductor region 7). The isolation well regions 35 may also be referred to as "third well regions," "first isolation well regions," etc. A source potential is applied to the isolation well regions 35. The number of isolation well regions 35 is less than the number of isolation structures 30.

[0375] The isolation well region 35 has a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the isolation well region 35 may be higher than the p-type impurity concentration of the body region 10 or may be lower than the p-type impurity concentration of the body region 10.

[0376] The p-type impurity concentration of the isolation well region 35 may be approximately equal to the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the isolation well region 35 may be higher than the p-type impurity concentration of the gate well region 25, or may be lower than the p-type impurity concentration of the gate well region 25.

[0377] The p-type impurity concentration of the isolation well region 35 may be approximately equal to the p-type impurity concentration of the source well region 26. The p-type impurity concentration of the isolation well region 35 may be higher than the p-type impurity concentration of the source well region 26, or may be lower than the p-type impurity concentration of the source well region 26. The p-type impurity (trivalent element) of the isolation well region 35 is preferably aluminum.

[0378] The plurality of isolation well regions 35 are formed in regions below (specifically, directly below) the plurality of isolation structures 30 so as to be adjacent to one another in the horizontal direction within the second semiconductor region 7. The plurality of isolation well regions 35 are formed in regions below a plurality (four in this embodiment) of the plurality of isolation structures 30 that are located on the active region 8 side.

[0379] The multiple isolation well regions 35 are each formed in a thickness range between the bottom of the second semiconductor region 7 and the bottom walls of the multiple isolation structures 30, and overlap the multiple isolation structures 30 in a one-to-one correspondence in the thickness direction.

[0380] The plurality of isolation well regions 35 extend in a strip shape along the corresponding isolation structures 30 in plan view. The plurality of isolation well regions 35 have portions that extend in a first direction X along the corresponding isolation structures 30 in plan view, and portions that extend in a second direction Y along the corresponding isolation structures 30. In this embodiment, the plurality of isolation well regions 35 each extend in a polygonal ring shape (a square ring in this embodiment) along the corresponding isolation structures 30 in plan view.

[0381] The plurality of isolation well regions 35 are formed at intervals in the horizontal direction from the plurality of gate well regions 25 and the plurality of source well regions 26. In this embodiment, the plurality of isolation well regions 35 are connected to one another in the horizontal direction. The plurality of isolation well regions 35 may be formed at intervals in the horizontal direction and may face one another in the horizontal direction with a part of the second semiconductor region 7 sandwiched therebetween.

[0382] The plurality of isolation well regions 35 are formed at intervals from the bottom of the second semiconductor region 7 toward the bottom wall sides of the plurality of isolation structures 30, and face the first semiconductor region 6 across a part of the second semiconductor region 7. The plurality of isolation well regions 35 each have an upper end located on the bottom wall side of the corresponding isolation structure 30, and a bottom located on the bottom side of the second semiconductor region 7.

[0383] The upper ends of the plurality of isolation well regions 35 may be connected to the bottom walls of the corresponding isolation structures 30. The upper ends of the plurality of isolation well regions 35 may extend along the side walls of the corresponding isolation structures 30 and be connected to the body region 10. The upper ends of the plurality of isolation well regions 35 may be formed at intervals from the bottom walls of the corresponding isolation structures 30 toward the bottom of the second semiconductor region 7.

[0384] The bottoms of the multiple isolation well regions 35 may be located on the bottom wall side of the corresponding isolation structure 30 relative to the intermediate portion of the second semiconductor region 7, or may be located on the bottom side of the second semiconductor region 7 (the side of the second main surface 4) relative to the intermediate portion of the second semiconductor region 7.

[0385] Each of the isolation well regions 35 has a bulging portion 35a. The bulging portion 35a extends horizontally in an arc shape from the region directly below the corresponding isolation structure 30 to both sides of the corresponding isolation structure 30. The bulging portions 35a are connected to each other in the horizontal direction. Each of the isolation well regions 35 is formed in a tapered shape from the bulging portion 35a to the bottom.

[0386] The isolation well region 35 may have a width greater than or less than the width of the isolation structure 30. The width of the isolation well region 35 may be greater than or less than the width of the gate structure 15. The width of the isolation well region 35 may be greater than or less than the width of the source structure 90.

[0387] The width of the isolation well region 35 may be approximately equal to the width of the gate well region 25. The width of the isolation well region 35 may be greater than the width of the gate well region 25 or less than the width of the gate well region 25. The width of the isolation well region 35 may be approximately equal to the width of the source well region 26. The width of the isolation well region 35 may be greater than the width of the source well region 26 or less than the width of the source well region 26.

[0388] The width of the separation well region 35 may be 0.1 μm or more and 2 μm or less. The width of the separation well region 35 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.25 μm or less, 0.25 μm or more and 0.5 μm or less, 0.5 μm or more and 0.75 μm or less, 0.75 μm or more and 1 μm or less, 1 μm or more and 1.25 μm or less, 1.25 μm or more and 1.5 μm or less, 1.5 μm or more and 1.75 μm or less, and 1.75 μm or more and 2 μm or less.

[0389] The isolation well region 35 may have a depth approximately equal to that of the gate well region 25. The depth of the isolation well region 35 is the depth of the isolation well region 35 when referenced to the bottom wall of the isolation structure 30. The bottom of the isolation well region 35 may be located at a depth approximately equal to that of the bottom of the gate well region 25. The depth of the isolation well region 35 may be greater than or less than the depth of the gate well region 25.

[0390] The depth of the isolation well region 35 may be approximately equal to the depth of the source well region 26. The bottom of the isolation well region 35 may be located at a depth approximately equal to the bottom of the source well region 26. The depth of the isolation well region 35 may be greater than or less than the depth of the source well region 26.

[0391] The depth of the separation well region 35 may be greater than 0 μm and less than or equal to 5 μm. The depth of the separation well region 35 may have a value belonging to at least one of the following ranges: greater than 0 μm and less than or equal to 1 μm, 1 μm to 1.5 μm, 1.5 μm to 2 μm, 2 μm to 2.5 μm, 2.5 μm to 3 μm, 3 μm to 3.5 μm, 3.5 μm to 4 μm, 4 μm to 4.5 μm, and 4.5 μm to 5 μm.

[0392] The isolation well region 35 may have an aspect ratio greater than 0 and less than or equal to 2. The aspect ratio of the isolation well region 35 is the ratio of the depth of the isolation well region 35 to the width of the isolation well region 35.

[0393] The aspect ratio may have a value belonging to at least one of the ranges of greater than 0 and less than or equal to 0.25, 0.25 or more and less than or equal to 0.5, 0.5 or more and less than or equal to 0.75, 0.75 or more and less than or equal to 1, 1 or more and less than or equal to 1.25, 1.25 or more and less than or equal to 1.5, 1.5 or more and less than or equal to 1.75, and 1.75 or more and less than or equal to 2.

[0394] The pitch of the centers of the isolation well regions 35 (the pitch of the isolation well regions 35) is approximately equal to the pitch of the isolation structures 30. In this embodiment, the pitch of the isolation well regions 35 is less than the pitch of the gate structures 15 and the source structures 90. The pitch of the isolation well regions 35 may be approximately equal to the pitch of the gate structures 15 and the source structures 90, or may be greater than the pitch of the gate structures 15 and the source structures 90.

[0395] In this embodiment, the pitch of the isolation well regions 35 is less than the pitch of the gate well regions 25 and the source well regions 26. The pitch of the isolation well regions 35 may be approximately equal to the pitch of the gate well regions 25 and the source well regions 26, or may be greater than the pitch of the gate well regions 25 and the source well regions 26.

[0396] The pitch of the separation well regions 35 may be 0.1 μm or more and 2.5 μm or less. The pitch of the separation well regions 35 may have a value belonging to at least one of the ranges of 0.1 μm or more and 0.25 μm or less, 0.25 μm or more and 0.5 μm or less, 0.5 μm or more and 1 μm or less, 1 μm or more and 1.25 μm or less, 1.25 μm or more and 1.5 μm or less, 1.5 μm or more and 1.75 μm or less, 1.75 μm or more and 2 μm or less, 2 μm or more and 2.25 μm or less, and 2.25 μm or more and 2.5 μm or less.

[0397] The isolation well region 35 forms a pn junction with the second semiconductor region 7. The isolation well region 35 expands a depletion layer into the second semiconductor region 7 when a reverse bias voltage is applied. The depletion layer originating from the isolation well region 35 expands in the horizontal and thickness directions and merges with the depletion layer originating from the body region 10 (inner portion of the active region 8). The isolation well region 35 expands the depletion layer originating from the body region 10 toward the periphery of the first main surface 3, thereby alleviating the electric field in the multiple isolation structures 30 (periphery portion of the active region 8).

[0398] The semiconductor device 1B includes one or more (five in this embodiment) isolation contact regions 37 formed in the chip 2 (second semiconductor region 7). The isolation contact regions 37 may also be referred to as "third contact regions," etc. A source potential is applied to the isolation contact regions 37. The isolation contact regions 37 have a p-type impurity concentration higher than the n-type impurity concentration of the second semiconductor region 7. The p-type impurity concentration of the isolation contact regions 37 is higher than the p-type impurity concentration of the body region 10.

[0399] The p-type impurity concentration of the isolation contact region 37 is higher than the p-type impurity concentration of the isolation well region 35. The p-type impurity concentration of the isolation contact region 37 is higher than the p-type impurity concentration of the gate well region 25. The p-type impurity concentration of the isolation contact region 37 is higher than the p-type impurity concentration of the source well region 26.

[0400] The p-type impurity concentration of the isolation contact region 37 may be approximately equal to the p-type impurity concentration of the gate contact region 27. The p-type impurity concentration of the isolation contact region 37 may be higher than the p-type impurity concentration of the gate contact region 27, or may be lower than the p-type impurity concentration of the gate contact region 27.

[0401] The p-type impurity concentration of the isolation contact region 37 may be approximately equal to the p-type impurity concentration of the source contact region 28. The p-type impurity concentration of the isolation contact region 37 may be higher than the p-type impurity concentration of the source contact region 28, or may be lower than the p-type impurity concentration of the source contact region 28.

[0402] The plurality of isolation contact regions 37 are formed in regions along the plurality of isolation structures 30 for the isolation well region 35. The plurality of isolation contact regions 37 are formed at intervals from one another in regions between the plurality of isolation structures 30, and face one another with part of the second semiconductor region 7 interposed therebetween. The plurality of isolation contact regions 37 may be connected to one another in the regions between the plurality of isolation structures 30.

[0403] The plurality of isolation contact regions 37 are formed spaced apart from the plurality of gate structures 15 and the plurality of source structures 90. The plurality of isolation contact regions 37 are formed in a one-to-one correspondence with the plurality of isolation structures 30. The plurality of isolation contact regions 37 are interposed in regions between the bottom wall of the corresponding isolation structure 30 and the bottom of the corresponding isolation well region 35, and extend in strips along the corresponding isolation structure 30.

[0404] Each of the plurality of isolation contact regions 37 has a portion that extends in the first direction X along the corresponding isolation structure 30 in plan view, and a portion that extends in the second direction Y along the corresponding isolation structure 30. In this embodiment, each of the plurality of isolation contact regions 37 extends in a polygonal ring shape (a square ring in this embodiment) along the corresponding isolation structure 30 in plan view.

[0405] The plurality of isolation contact regions 37 may be formed at intervals following the extension direction of the corresponding isolation structures 30. In this case, the plurality of isolation contact regions 37 may each extend in a strip shape following the extension direction of the corresponding isolation structures 30.

[0406] The plurality of isolation contact regions 37 are respectively connected to the bottom walls of the corresponding isolation structures 30 and the corresponding isolation well regions 35. The plurality of isolation contact regions 37 increase the p-type impurity concentration at the upper end portions of the corresponding isolation well regions 35. The plurality of isolation contact regions 37 extend from the regions directly below the isolation structures 30 to both sides of the isolation structures 30, and have extensions that extend along the sidewalls of the corresponding isolation structures 30.

[0407] The thickness in the horizontal direction (first direction X) of the portions (extensions) of the multiple isolation contact regions 37 that extend along the side walls of the isolation structure 30 may be less than the thickness in the vertical direction Z of the portions of the multiple isolation contact regions 37 that extend along the bottom wall of the isolation structure 30.

[0408] The extensions of the plurality of isolation contact regions 37 are electrically connected to the body region 10 in the surface layer portion of the first main surface 3, and electrically connect the corresponding isolation well regions 35 to the body region 10. This prevents the plurality of isolation well regions 35 from being electrically floating, and improves the electrical response characteristics of the plurality of isolation well regions 35.

[0409] The plurality of isolation contact regions 37 each have an upper end portion exposed from the first main surface 3. In this embodiment, the upper ends of the plurality of isolation contact regions 37 are exposed from the sidewall of the third trench 31 at the opening end of the third trench 31.

[0410] The upper ends of the multiple isolation contact regions 37 may extend horizontally in the surface layer portion of the body region 10. The upper ends of the multiple isolation contact regions 37 are electrically connected to each other within the body region 10. In this embodiment, the upper ends of the multiple isolation contact regions 37 are integrally formed within the body region 10.

[0411] The first outer well region 42 is formed deeper than the isolation well region 35 along the outer periphery boundary 19. The first outer well region 42 may also be approximately the same depth as the isolation well region 35.

[0412] In the horizontal direction along the first main surface 3, the first outer well region 42 partially covers at least the isolation well region 35 of the terminal third trench 31A.

[0413] More specifically, the isolation well region 35 includes a well side portion (in this embodiment, a bulging portion 35a) extending in the thickness direction of the second semiconductor region 7, and a well bottom portion 35b extending from the bulging portion 35a in a direction along the first main surface 3. The first outer well region 42 selectively covers the bulging portion 35a on the outer peripheral region 9 side (outside) of the isolation well region 35 of the terminal third trench 31A. The bulging portion 35a and the well bottom 35b on the active region 8 side (inside) that are not covered by the first outer well region 42 are covered by the second semiconductor region 7 (in this embodiment, a high-concentration region 72).

[0414] The outer contact region 41 extends in a strip shape along the terminal isolation structure 30A in the second direction Y. In this embodiment, the inner edge of the outer contact region 41 is connected to the terminal isolation structure 30A. In this embodiment, the inner edge of the outer contact region 41 is connected to the isolation well region 35 of the terminal third trench 31A. The inner edge of the outer contact region 41 extends along the terminal isolation structure 30A (peripheral boundary 19) in the thickness direction of the second semiconductor region 7 and is connected to the isolation well region 35 of the terminal third trench 31A. The first outer well region 42 is electrically connected to the body region 10 via the isolation well region 35 of the terminal third trench 31A.

[0415] The semiconductor device 1B includes an outer wiring 46 disposed on the main surface insulating film 45 in the peripheral region 9. The outer wiring 46 may also be referred to as "wiring," "main surface wiring," "peripheral wiring," "side wiring," etc. The outer wiring 46 may include either or both of p-type conductive polysilicon and n-type conductive polysilicon. The outer wiring 46 preferably has the same type of conductive material (conductivity type) as at least one of the first buried electrode 18, the second buried electrode 93, and the third buried electrode 33.

[0416] The outer wiring 46 is arranged in the peripheral region 9 at a distance from the periphery of the first main surface 3 toward the active region 8. The outer wiring 46 is arranged on the outer well region 40 (first outer well region 42) and faces the first outer well region 42 with the main surface insulating film 45 interposed therebetween.

[0417] The outer wiring 46 extends in a strip shape along the periphery of the first main surface 3 (the periphery of the active region 8) in the same direction as the first outer well region 42 in a plan view. The outer wiring 46 has a portion extending in the first direction X and a portion extending in the second direction Y.

[0418] In this embodiment, the outer wiring 46 is formed in a polygonal ring shape (a square ring shape in this embodiment) having four sides parallel to the periphery of the chip 2 in a plan view, and surrounds the inner portion (active region 8) of the first main surface 3. The outer wiring 46 may have an edge portion that connects the portion extending in the first direction X and the portion extending in the second direction Y in an arc shape (preferably a quadrant arc shape). The outer wiring 46 may be either terminated or endless.

[0419] The outer wiring 46 has an inner edge portion on the inner side (active region 8 side) of the first main surface 3 and an outer edge portion on the peripheral side of the first main surface 3. The inner edge portion of the outer wiring 46 is drawn out from the outer periphery region 9 into the active region 8. The inner edge portion of the outer wiring 46 covers one or more isolation structures 30 and is connected to one or more isolation structures 30.

[0420] In this embodiment, the inner edge of the outer wiring 46 covers the terminal isolation structure 30A and is connected to the third buried electrode 33 of the terminal isolation structure 30A.

[0421] The outer wiring 46 may be connected to at least one or all of the plurality of isolation structures 30 for the isolation well region 35. The outer wiring 46 is formed integrally with the third buried electrode 33 of the isolation structure 30. In other words, the outer wiring 46 is formed as an extension portion of the third buried electrode 33, and is routed over the main surface insulating film 45.

[0422] The outer edge of the outer wiring 46 is formed at a distance inward from the outer edge of the first outer well region 42. In this embodiment, the outer edge of the outer wiring 46 is disposed at a distance inward from the outer edge of the outer contact region 41, and has a portion facing the outer contact region 41 across the main surface insulating film 45. The outer edge of the outer wiring 46 may have a portion facing the first outer well region 42 in the stacking direction.

[0423] The semiconductor device 1B includes a plurality of gate openings 48 formed in an interlayer film 47 in the active region 8 (see FIG. 22 ). The plurality of gate openings 48 are formed in a one-to-many correspondence with a corresponding one of the gate structures 15. In this embodiment, the plurality of gate openings 48 penetrate the interlayer film 47 and expose one end or the other end of each of the plurality of gate structures 15 (first buried electrodes 18). The arrangement of the gate openings 48 relative to the gate structures 15 shown in FIG. 22 may be applied to the gate structure 15 of FIG. 3 .

[0424] The plurality of gate openings 48 may each have an opening end curved in an arc shape. The plurality of gate openings 48 may be formed in a quadrangular shape, a rectangular shape (strip shape) extending in the first direction X, a rectangular shape (strip shape) extending in the second direction Y, a circular shape, or the like in a plan view. The plurality of gate openings 48 may each have an opening end curved in an arc shape.

[0425] The semiconductor device 1B includes a plurality of source openings 49 formed in the interlayer film 47 in the active region 8. The plurality of source openings 49 are formed in a portion of the interlayer film 47 that covers the active region 8. The plurality of source openings 49 are formed in a one-to-one correspondence with the plurality of source structures 90 in regions between the plurality of gate structures 15. The plurality of source openings 49 each extend in a strip shape in the second direction Y along the corresponding source structure 90.

[0426] The plurality of source openings 49 penetrate the main surface insulating film 45 and the interlayer film 47, and expose a corresponding source structure 90, a source region 11, a plurality of gate contact regions 27, and a plurality of source contact regions 28. Each of the plurality of source openings 49 may have an opening end curved in an arc shape.

[0427] The plurality of source openings 49 may be formed in a one-to-many correspondence with a corresponding one of the source structures 90. In this case, the plurality of source openings 49 may be formed at intervals along the corresponding one of the source structures 90. In this case, the plurality of source openings 49 may be formed in a quadrangular shape, a rectangular shape (strip shape), a circular shape, or the like in a plan view.

[0428] 27 , the semiconductor device 1B has a two-layer structure including a lower layer made of a first region 12 with a relatively low concentration and an upper layer made of a second region 13 with a relatively higher concentration than the first region 12. This allows the depletion layer to extend along the first main surface 3 to the first side 42d (outer end) of the first outer well region 42. As a result, the electric field with respect to the terminal isolation structure 30A and the bottom of the isolation structure 30 near the terminal isolation structure 30A can be alleviated, thereby suppressing a decrease in breakdown voltage due to electric field concentration. In other words, a decrease in breakdown voltage originating from the peripheral boundary 19 between the active region 8 and the peripheral region 9 can be suppressed.

[0429] Furthermore, similar to the semiconductor device 1A, the high concentration region 72 extends along the first main surface 3, across the outer boundary 19, and into the first outer well region 42, providing an n-type background concentration to the first outer well region 42. In this manner, by selectively increasing the n-type background concentration of the first outer well region 42, it is possible to increase the dielectric breakdown field value of the first outer well region 42. As a result, it is possible to improve the avalanche resistance.

[0430] The above-described embodiment (including its modified examples) can be implemented in other embodiments. For example, in the above-described second embodiment, the outer wiring 46 is connected to the source electrode 51. However, the outer wiring 46 may be electrically separated from the source electrode 51. In this case, the outer wiring 46 may be formed in an electrically floating state as a floating wiring or a field wiring (a so-called field preplate).

[0431] In the above-described embodiments, the chip 2 includes a SiC single crystal. However, the chip 2 may include a silicon single crystal. Similarly, the first semiconductor region 6 may include a silicon single crystal. Similarly, the second semiconductor region 7 may include a silicon single crystal.

[0432] In each of the above-described embodiments, a structure may be adopted in which the conductivity type of an “n-type” semiconductor region is inverted to “p-type” and the conductivity type of a “p-type” semiconductor region is inverted to “n-type.” A specific configuration in this case can be obtained by replacing “n-type” with “p-type” and “p-type” with “n-type” in the above description and accompanying drawings.

[0433] In each of the above-described embodiments, a p-type collector region may be formed in a surface layer portion of the second main surface 4 of the chip 2. In this case, the transistor structure Tr includes an IGBT (Insulated Gate Bipolar Transistor) structure instead of the MISFET structure. A specific configuration in this case can be obtained by replacing the "source" of the MISFET structure with the "emitter" of the IGBT structure and the "drain" of the MISFET structure with the "collector" of the IGBT structure in the above description. In this case, the chip 2 may have a single-layer structure made of an n-type semiconductor substrate.

[0434] Below, examples of features extracted from this specification and the drawings are shown. Below, alphanumeric characters in parentheses represent corresponding components in the above-mentioned embodiments, but are not intended to limit the scope of each clause to the embodiments. The "semiconductor device" in the following items may be replaced with "semiconductor device," "wide bandgap semiconductor device," "semiconductor switching device," "semiconductor rectifier device," "MISFET device," "IGBT device," "diode device," etc., as necessary.

[0435] [Supplementary Note 1-1] A SiC chip (2) having a main surface (3), a semiconductor region (7) of a first conductivity type formed in a surface layer portion of the main surface (3), an active region (8) provided in the main surface (3), an outer peripheral region (9) provided in the main surface (3) and surrounding the periphery of the active region (8), a device structure (Tr) formed in the active region (8), the device structure (Tr) including a body region (10) of a second conductivity type formed in a surface layer portion of the semiconductor region (7) and a source region (11) of a first conductivity type formed in a surface layer portion of the body region (10), and an outer well region (40) of a second conductivity type formed in a surface layer portion of the semiconductor region (7) in the outer peripheral region (9), the outer well region (40) including a first outer well region (42) formed along a peripheral boundary portion (19) between the active region (8) and the outer peripheral region (9), The semiconductor device (1A, 1B) includes a first region (12) having a first impurity concentration, and a second region (13) formed closer to the main surface (3) than the first region (12) and having a second impurity concentration higher than the first impurity concentration.

[0436] [Supplementary Note 1-2] The semiconductor device (1A, 1B) according to Supplementary Note 1-1 further includes a trench structure (15) extending from the main surface (3) toward the inside of the semiconductor region (7) in the active region (8), and the first outer well region (42) has a layer structure of a second conductivity type including a lower layer made of the first region (12) and an upper layer made of the second region (13).

[0437] [Appendix 1-3] The semiconductor device (1A, 1B) according to appendix 1-2, wherein the second region (13) has an outer end (13a) located at the outer end (42d) of the first outer well region (42).

[0438] [Appendix 1-4] The semiconductor device (1A, 1B) according to Appendix 1-2 or Appendix 1-3, further comprising a bottom well region (25) of a second conductivity type formed at the bottom of the trench structure (15), and the first outer well region (42) is formed so as to cover a portion of the bottom well region (25).

[0439] [Appendix 1-5] The semiconductor device (1A, 1B) according to Appendix 1-4, further comprising an outer contact region (41) formed in a surface layer portion of the second region (13) and having a higher impurity concentration than the second region (13) and the first region (12), the outer contact region (41) extending along the trench structure (15) in a thickness direction of the semiconductor region (7) and connected to the bottom well region (25).

[0440] [Appendix 1-6] The semiconductor device (1A, 1B) according to Appendix 1-5, wherein a boundary (60) between the first region (12) and the second region (13) extends along the main surface (3) from a portion of the outer contact region (41) that contacts a side of the trench structure (15).

[0441] [Supplementary Note 1-7] The semiconductor device (1A, 1B) according to any one of Supplementary Note 1-2 to Supplementary Note 1-6, wherein the device structure (Tr) includes a plurality of gate trenches (16) arranged in a stripe pattern, each of which penetrates the source region (11) and the body region (10) to reach the semiconductor region (7), a gate insulating film (17) formed on the inner surface of the gate trenches (16), and a plurality of trench gate structures (15) having gate electrodes (18) embedded in the gate trenches (16) via the gate insulating film (17), and the plurality of trench gate structures (15) are formed as a plurality of the trench structures (15).

[0442] [Appendix 1-8] The semiconductor device (1A) according to Appendix 1-7, wherein a terminal gate trench (16A) consisting of the gate trench (16) of the outermost trench gate structure (15A) among the plurality of trench gate structures (15) is a boundary trench separating the active region (8) and the peripheral region (9).

[0443] [Note 1-9] The second region (13) has a second conductivity type impurity concentration of 1×10 １７ cm －３ 1x10 or more １８ cm －３ the impurity concentration of the second conductivity type in the first region (12) is 1×10１６ cm －３ 1x10 or more １７ cm －３ The semiconductor device (1A, 1B) according to any one of Supplementary Notes 1-1 to 1-8 below.

[0444] [Appendix 1-10] The semiconductor device (1A, 1B) according to any one of Appendices 1-1 to 1-9, wherein the first outer well region (42) has a first upper end (42a) on the main surface (3) side and a first lower end (42b) on the opposite side thereof, and has a first concentration gradient of the second conductivity type that gradually decreases from the first upper end (42a) toward the first lower end (42b).

[0445] [Appendix 1-11] The semiconductor device (1A, 1B) described in Appendix 1-10, wherein the first concentration gradient includes a peak value (P2) on the side of the first upper end (42a) and a gradual portion (22) in which the impurity concentration gradually decreases at a gradual rate of decrease in a region closer to the first lower end (42b) than the peak value (P2).

[0446] [Supplementary Note 1-12] The semiconductor device (1A, 1B) according to Supplementary Note 1-11, wherein the gentle portion (22) occupies a thickness range of at least ¼ of the first outer well region (42).

[0447] [Appendix 1-13] The semiconductor device (1A, 1B) according to appendix 1-12, wherein the gentle portion (22) has a thickness of 0.5 μm or more and 2.0 μm or less, and has a concentration reduction rate of 50% or less within the thickness range.

[0448] [Appendix 1-14] The semiconductor device (1A, 1B) according to any one of Appendices 1-10 to 1-13, wherein the first outer well region (42) has a first side (42d) that connects the first lower end (42b) and the first upper end (42a) and slopes toward the active region (8) from the first upper end (42a) toward the first lower end (42b).

[0449] [Supplementary Note 1-15] The semiconductor device (1A, 1B) according to any one of Supplementary Note 1-1 to Supplementary Note 1-14, wherein the outer well region (40) is formed in a ring shape surrounding the active region (8).

[0450] [Appendix 1-16] The semiconductor device (1A, 1B) according to any one of Appendices 1-1 to 1-15, wherein the outer well region (40) is formed outside the first outer well region (42) and physically and electrically isolated from the second region (13), and includes a plurality of second outer well regions (43) surrounding the first outer well region (42).

[0451] [Appendix 1-17] The semiconductor device (1A, 1B) according to Appendix 1-16, wherein the plurality of second outer well regions (43) have the same depth as the first outer well region (42), and the second outer well region (43) has a second upper end (43a) on the main surface (3) side and a second lower end (43b) on the opposite side thereof, and has a second concentration gradient of the second conductivity type that gradually decreases from the second upper end (43a) to the second lower end (43b).

[0452] [Appendix 1-18] The semiconductor device (1A, 1B) according to Appendix 1-16 or Appendix 1-17, wherein the second outer well region (43) is formed in a mesa shape in cross section, having a second side portion (43d) that connects the second lower end portion (43b) and the second upper end portion (43a) and that slopes so that its width narrows from the second upper end portion (43a) toward the second lower end portion (43b).

[0453] [Appendix 1-19] The semiconductor device (1A, 1B) according to any one of Appendices 1-2 to 1-8, wherein the semiconductor region (7) includes a base region (71) spanning the active region (8) and the peripheral region (9), and a high-concentration region (72) having a higher impurity concentration than the base region (71), the high-concentration region (72) being formed in the active region (8) on a surface layer of the base region (71) so as to cover a bottom of the trench structure (15).

[0454] [Appendix 1-20] The semiconductor device (1A, 1B) according to Appendix 1-19, wherein a background concentration gradient of the first conductivity type impurity in the first outer well region (42) in a depth direction of the SiC chip (2) is equal to a concentration gradient of the first conductivity type impurity concentration in the high concentration region (72) in the same direction.

[0455] [Appendix 1-21] The semiconductor device (1A, 1B) according to any one of Appendices 1-1 to 1-20, wherein a chip concentration gradient of the first conductivity type impurity concentration when crossing the first outer well region (42) from the main surface (3) in a depth direction of the SiC chip (2) includes a high concentration section (97) within the first outer well region (42) and a low concentration section (98) outside the first outer well region (42) that is lower in concentration than the high concentration section (97).

[0456] [Supplementary Note 2-1] A SiC chip (2) having a main surface (3), a semiconductor region (7) of a first conductivity type formed in a surface layer portion of the main surface (3), an active region (8) provided on the main surface (3) and having a device structure (Tr) formed therein, a peripheral region (9) provided on the main surface (3) and surrounding the periphery of the active region (8), a device structure (Tr) formed in the active region (8), the device structure (Tr) including a body region (10) of a second conductivity type formed in a surface layer portion of the semiconductor region (7) and a source region (11) of a first conductivity type formed in a surface layer portion of the body region (10), and an outer well region (40) of a second conductivity type formed in a surface layer portion of the semiconductor region (7) in the peripheral region (9), the outer well region (40) including a first outer well region (42) formed along a peripheral boundary (19) between the active region (8) and the peripheral region (9), The semiconductor device (1A, 1B) according to Appendix 1-19, wherein the semiconductor region (7) includes a base region (71) spanning the active region (8) and the peripheral region (9), and a high-concentration region (72) formed in the active region (8) in a surface layer portion of the base region (71) and having a higher impurity concentration than the base region (71), and wherein, in a depth direction of the SiC chip (2), a background concentration gradient of the first conductivity type impurity in the first outer well region (42) includes a concentration gradient equal to a concentration gradient of the first conductivity type impurity concentration in the high-concentration region (72) in the same direction.

[0457] [Supplementary Note 2-2] The impurity concentration of the high concentration region (72) and the background impurity concentration are 1×10 １７ cm －３ 1x10 or more１８ cm －３ The impurity concentration of the base region (71) is 1×10 or less. １６ cm －３ 1x10 or more １７ cm －３ The following is the semiconductor device (1A, 1B) in Appendix 2-1.

[0458] [Supplementary Note 2-3] A SiC chip (2) having a main surface (3), a semiconductor region (7) of a first conductivity type formed in a surface layer portion of the main surface (3), an active region (8) provided on the main surface (3) and having a device structure (Tr) formed therein, a peripheral region (9) provided on the main surface (3) and surrounding the periphery of the active region (8), the device structure (Tr) formed in the active region (8), the device structure (Tr) including a body region (10) of a second conductivity type formed in a surface layer portion of the semiconductor region (7) and a source region (11) of a first conductivity type formed in a surface layer portion of the body region (10), and an outer well region (40) of a second conductivity type formed in a surface layer portion of the semiconductor region (7) in the peripheral region (9), the outer well region (40) including a first outer well region (42) formed along a peripheral boundary (19) between the active region (8) and the peripheral region (9), A semiconductor device (1A, 1B) wherein a first chip concentration gradient of a first conductivity type impurity concentration when crossing the first outer well region (42) from the main surface (3) in a depth direction of the SiC chip (2) includes a high concentration section (97) within the first outer well region (42) and a low concentration section (98) outside the first outer well region (42) that is lower in concentration than the high concentration section (97).

[0459] [Supplementary Note 2-4] The impurity concentration of the first conductivity type in the high concentration section (97) is 1×10 １７ cm －３ 1x10 or more １８ cm －３ the impurity concentration of the first conductivity type in the low concentration section (98) is 1×10 １６ cm －３ 1x10 or more １７ cm －３ The following is the semiconductor device (1A, 1B) in Appendix 2-3.

[0460] [Supplementary Note 2-5] The semiconductor device (1A, 1B) according to Supplementary Note 2-3 or Supplementary Note 2-4, wherein a second chip concentration gradient of the first conductivity type impurity concentration when passing through a side of the first outer well region (42) from the main surface (3) in a depth direction of the SiC chip (2) includes a concentration gradient equal to that of the low concentration section (98) over the entire section adjacent to the first outer well region (42).

[0461] [Supplementary Note 2-6] The semiconductor device (1A, 1B) according to any one of Supplementary Note 2-1 to Supplementary Note 2-5, wherein the device structure (Tr) includes a plurality of gate trenches (16) arranged in a stripe pattern, the gate trenches (16) penetrating the source region (11) and the body region (10) to reach the semiconductor region (7), gate insulating films (17) formed on the inner surfaces of the plurality of gate trenches (16), and gate electrodes (18) embedded in the plurality of gate trenches (16) via the gate insulating films (17).

[0462] [Appendix 2-7] The semiconductor device (1A) according to Appendix 2-6, wherein an end gate trench (16A) consisting of the gate trench (16) of the outermost trench gate structure (15A) among the plurality of trench gate structures (15) is a boundary trench separating the active region (8) and the peripheral region (9).

[0463] [Appendix 2-8] The semiconductor device (1A, 1B) according to any one of Appendices 2-1 to 2-7, wherein the first outer well region (42) has a first upper end (42a) on the main surface (3) side and a first lower end (42b) on the opposite side thereof, and has a first concentration gradient of the second conductivity type that gradually decreases from the first upper end (42a) toward the first lower end (42b).

[0464] [Appendix 2-9] The semiconductor device (1A, 1B) according to Appendix 2-8, wherein the first concentration gradient includes a peak value on the side of the first upper end (42 a) and a gradual portion (22) in which the impurity concentration gradually decreases at a gradual rate of decrease in a region on the side of the first lower end (42 b) from the peak value.

[0465] [Supplementary Note 2-10] The semiconductor device (1A, 1B) according to Supplementary Note 2-9, wherein the gentle portion (22) occupies a thickness range of at least ¼ of the first outer well region (42).

[0466] [Appendix 2-11] The semiconductor device (1A, 1B) according to appendix 2-10, wherein the gentle portion (22) has a thickness of 0.5 μm or more and 2.0 μm or less, and has a concentration reduction rate of 50% or less within the thickness range.

[0467] [Appendix 2-12] The semiconductor device (1A, 1B) according to any one of Appendices 2-8 to 2-11, wherein the first outer well region (42) has a first side (42d) that connects the first lower end (42b) and the first upper end (42a) and slopes toward the active region (8) from the first upper end (42a) to the first lower end (42b).

[0468] [Supplementary Note 2-13] The semiconductor device (1A, 1B) according to any one of Supplementary Note 2-1 to Supplementary Note 2-12, wherein the outer well region (40) is formed in a ring shape surrounding the active region (8).

[0469] [Appendix 2-14] The semiconductor device (1A, 1B) according to any one of Appendices 2-1 to 2-13, wherein the outer well region (40) is formed outside the first outer well region (42) and includes a plurality of second outer well regions (43) surrounding the first outer well region (42).

[0470] [Appendix 2-15] The semiconductor device (1A, 1B) according to Appendix 2-14, wherein the plurality of second outer well regions (43) have the same depth as the first outer well region (42), and the second outer well region (43) has a second upper end (43a) on the main surface (3) side and a second lower end (43b) on the opposite side thereof, and has a second concentration gradient of the second conductivity type that gradually decreases from the second upper end (43a) to the second lower end (43b).

[0471] [Appendix 2-16] The semiconductor device (1A, 1B) according to Appendix 2-14 or Appendix 2-15, wherein the second outer well region (43) is formed in a mesa shape in cross section, having a second side portion (43d) that connects the second lower end portion (43b) and the second upper end portion (43a) and that slopes so that its width narrows from the second upper end portion (43a) toward the second lower end portion (43b).

[0472] 1A: Semiconductor device 1B: Semiconductor device 2: Chip 3: First main surface 4: Second main surface 5A: First side surface 5B: Second side surface 5C: Third side surface 5D: Fourth side surface 6: First semiconductor region 7: Second semiconductor region 8: Active region 9: Peripheral region 10: Body region 11: Source region 12: First region 12a: Outer end 12b: Inner end 12c: Bottom 13: Second region 13a: Outer end 14: Extension 15: Gate structure 15A: Terminal gate structure 16: First trench 16A: Terminal first trench 17: First insulating film 17A: Terminal first insulating film 18: First buried electrode 18A: Terminal first buried electrode 19 : Peripheral boundary portion 20 : Gradual increase portion 21 : Peak portion 22 : Gradual decrease portion 23 : Gradual decrease portion 25 : Gate well region 25a : Bulging portion 25b : Well bottom 26 : Source well region 26a : Bulging portion 27 : Gate contact region 28 : Source contact region 30 : Isolation structure 30A : Terminal isolation structure 31 : Third trench 31A : Terminal third trench 32 : Third insulating film 32A : Terminal third insulating film 33 : Third buried electrode 33A : Terminal third buried electrode 35 : Isolation well region 35a : Bulging portion 35b : Well bottom 37 : Isolation contact region 40 : Outer well region 41 : Outer contact region 42 : First outer well region 42a : First upper end portion 42b : First lower end 42c : First main body portion 42d : First side portion 43 : Second outer well region 43a : Second upper end 43b : Second lower end 43c : Second main body portion 43d : Second side portion 45 : Main surface insulating film 46 : Outer wiring 47 : Interlayer film 48 : Gate opening 49 : Source opening 50 : Outer opening 51 : Source electrode 51a : First pad portion 51b : Second pad portion 51c : Third pad portion 52 : Lower electrode film 53 : Main electrode film 56 : Source wiring 57 : Gate electrode 58 : Gate wiring 59 : Drain electrode 60 : Boundary portion 62 : Boundary portion 63 : Central portion 64 : End portion 65 : Gap 66 : Central portion 67 : End portion68: Gap 71: Base region 72: High concentration region 73: Rapid increase portion 74: Peak portion 75: Rapid decrease portion 76: First concentration gradient 77: Second concentration gradient 78: Concentration gradient 85: Gradual increase portion 86: Peak portion 87: Gradual decrease portion 88: Gradual decrease portion 90: Source structure 91: Second trench 92: Second insulating film 93: Second buried electrode 94: Rapid increase portion 95: Peak portion 96: Rapid decrease portion 97: High concentration section 98: Low concentration section 99: Concentration gradient

Claims

1. A semiconductor device comprising: a SiC chip having a main surface; a semiconductor region of a first conductivity type formed in a surface layer portion of the main surface; an active region provided on the main surface; a peripheral region provided on the main surface and surrounding the periphery of the active region; a device structure formed in the active region, the device structure including a body region of a second conductivity type formed in a surface layer portion of the semiconductor region and a source region of the first conductivity type formed in a surface layer portion of the body region; and an outer well region of a second conductivity type formed in a surface layer portion of the semiconductor region in the peripheral region, the outer well region including a first outer well region formed along the peripheral boundary between the active region and the peripheral region, the first outer well region including a first region having a first impurity concentration, and a second region formed closer to the main surface than the first region and having a second impurity concentration higher than the first impurity concentration.

2. The semiconductor device according to claim 1, further comprising a trench structure in said active region extending from said main surface into said semiconductor region, and said first outer well region having a layer structure of a second conductivity type including a lower layer made of said first region and an upper layer made of said second region.

3. The semiconductor device according to claim 2, wherein said second region has an outer end located at an outer end of said first outer well region.

4. The semiconductor device according to claim 2 or 3, further comprising a bottom well region of a second conductivity type formed at the bottom of said trench structure, said first outer well region being formed so as to cover a portion of said bottom well region.

5. The semiconductor device according to claim 4, further comprising an outer contact region formed in a surface layer portion of the second region and having a higher impurity concentration than the second region and the first region, the outer contact region extending along the trench structure in the thickness direction of the semiconductor region and connected to the bottom well region.

6. The semiconductor device according to claim 5, wherein the boundary between said first region and said second region extends along said main surface from a portion of said outer contact region that contacts a side portion of said trench structure.

7. The semiconductor device according to any one of claims 2 to 6, wherein the device structure includes a plurality of gate trenches arranged in a stripe pattern, which penetrate through the source region and the body region to reach the semiconductor region, a gate insulating film formed on the inner surface of the plurality of gate trenches, and a plurality of trench gate structures each having a gate electrode embedded in the plurality of gate trenches via the gate insulating film, and the plurality of trench gate structures are formed as a plurality of the trench structures.

8. The semiconductor device according to claim 7, wherein an end gate trench consisting of the gate trench of the outermost trench gate structure among the plurality of trench gate structures is a boundary trench separating the active region from the peripheral region.

9. The second region has a second conductivity type impurity concentration of 1×10 １７ cm －３ 1x10 or more １８ cm －３ the impurity concentration of the second conductivity type in the first region is 1×10 １６ cm －３ 1x10 or more １７ cm －３ 9. The semiconductor device according to claim 1, wherein:

10. A semiconductor device according to any one of claims 1 to 9, wherein the first outer well region has a first upper end on the main surface side and a first lower end on the opposite side, and has a first concentration gradient of the second conductivity type that gradually decreases from the first upper end toward the first lower end.

11. The semiconductor device according to claim 10, wherein the first concentration gradient includes a peak value on the first upper end side and a gradual portion in which the impurity concentration gradually decreases at a gradual rate of decrease in a region on the first lower end side of the peak value.

12. The semiconductor device according to claim 11, wherein the loose portion occupies a thickness range of at least one-fourth of the first outer well region.

13. The semiconductor device according to claim 12, wherein the gradual portion has a thickness of 0.5 μm or more and 2.0 μm or less, and has a concentration reduction rate of 50% or less within this thickness range.

14. A semiconductor device according to any one of claims 10 to 13, wherein the first outer well region has a first side portion that connects the first lower end portion and the first upper end portion and slopes from the first upper end portion toward the active region from the first lower end portion.

15. The semiconductor device according to any one of claims 1 to 14, wherein the outer well region is formed in a ring shape surrounding the active region.

16. A semiconductor device according to any one of claims 1 to 15, wherein the outer well region is formed outside the first outer well region and physically and electrically isolated from the second region, and includes a plurality of second outer well regions surrounding the first outer well region.

17. The semiconductor device described in claim 16, wherein the plurality of second outer well regions have the same depth as the first outer well region, and the second outer well region has a second upper end on the main surface side and a second lower end on the opposite side, and has a second concentration gradient of the second conductivity type that gradually decreases from the second upper end toward the second lower end.

18. A semiconductor device as described in claim 16 or 17, wherein the second outer well region is formed in a mesa shape in cross section, connecting the second lower end and the second upper end, and having a second side portion that slopes so that its width narrows from the second upper end toward the second lower end.

19. A semiconductor device according to any one of claims 2 to 8, wherein the semiconductor region includes a base region spanning the active region and the peripheral region, and a high-concentration region formed in the active region on a surface layer of the base region so as to cover the bottom of the trench structure and having a higher impurity concentration than the base region.

20. The semiconductor device according to claim 19, wherein a background concentration gradient of the first conductivity type impurity in the first outer well region in the depth direction of the SiC chip is equal to a concentration gradient of the first conductivity type impurity concentration in the high concentration region in the same direction.

21. A semiconductor device according to any one of claims 1 to 20, wherein a chip concentration gradient of the first conductivity type impurity concentration when crossing the first outer well region from the main surface in the depth direction of the SiC chip includes a high concentration section within the first outer well region and a low concentration section outside the first outer well region that is lower in concentration than the high concentration section.

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