JP2017050516A - Silicon carbide semiconductor device - Google Patents

Silicon carbide semiconductor device Download PDF

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JP2017050516A
JP2017050516A JP2015175131A JP2015175131A JP2017050516A JP 2017050516 A JP2017050516 A JP 2017050516A JP 2015175131 A JP2015175131 A JP 2015175131A JP 2015175131 A JP2015175131 A JP 2015175131A JP 2017050516 A JP2017050516 A JP 2017050516A
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electric field
trench gate
field relaxation
semiconductor device
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JP6453188B2 (en
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佐智子 青井
Sachiko Aoi
佐智子 青井
侑佑 山下
Yusuke Yamashita
侑佑 山下
渡辺　行彦
Yukihiko Watanabe
行彦 渡辺
雅裕 杉本
Masahiro Sugimoto
雅裕 杉本
康裕 海老原
Yasuhiro Ebihara
康裕 海老原
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Denso Corp
Toyota Motor Corp
Toyota Central R&D Labs Inc
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Toyota Motor Corp
Toyota Central R&D Labs Inc
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    • H01L29/0696—Surface layout of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
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Abstract

PROBLEM TO BE SOLVED: To provide a silicon carbide semiconductor device which has a low saturation current.SOLUTION: A silicon carbide semiconductor device 1 includes a semiconductor substrate 10 which has: an ntype drift region 12; a ptype electric field relaxation region 13 which is provided on the drift region 12 and provided so as to cover a bottom face of a trench gate 30; an ntype current dispersion region 14 which is provided on the electric field relaxation region 13 and contacts a lateral face of the trench gate 30 and the drift region 12; a ptype body region 15 which is provided on the current dispersion region 14 and contacts the lateral face of the trench gate 30; and an ntype source region 17 which is provided on the body region 15 and contacts the lateral face of the trench gate 30. The electric field relaxation region 13 is formed to be short circuited with the body region 15.SELECTED DRAWING: Figure 1

Description

本明細書で開示する技術は、トレンチゲートを備える炭化珪素半導体装置に関する。   The technology disclosed in this specification relates to a silicon carbide semiconductor device including a trench gate.

特許文献１は、トレンチゲートの底面を覆うように設けられているｐ型の電界緩和領域を備える炭化珪素半導体装置を開示する。このような電界緩和領域は、トレンチゲートの底面に集中する電界を緩和することができる。これにより、炭化珪素半導体装置の耐圧が向上する。特許文献１はさらに、そのような電界緩和領域によってチャネル抵抗が増加するのを抑えるために、ドリフト領域よりも不純物濃度が濃いｎ型の電流分散領域を設ける技術を提案する。電流分散領域は、電界緩和領域上に設けられており、トレンチゲートの側面とドリフト領域の双方に接するように配置されている。これにより、電流は、電界緩和領域を迂回するように電流分散領域を介して流れることができる。このため、特許文献１に開示される炭化珪素半導体装置は、高耐圧と低オン抵抗を両立することができる。   Patent Document 1 discloses a silicon carbide semiconductor device including a p-type electric field relaxation region provided so as to cover the bottom surface of a trench gate. Such an electric field relaxation region can relax an electric field concentrated on the bottom surface of the trench gate. Thereby, the breakdown voltage of the silicon carbide semiconductor device is improved. Patent Document 1 further proposes a technique of providing an n-type current distribution region having an impurity concentration higher than that of the drift region in order to suppress an increase in channel resistance due to such an electric field relaxation region. The current distribution region is provided on the electric field relaxation region and is disposed so as to contact both the side surface of the trench gate and the drift region. Thereby, the current can flow through the current dispersion region so as to bypass the electric field relaxation region. For this reason, the silicon carbide semiconductor device disclosed in Patent Document 1 can achieve both high breakdown voltage and low on-resistance.

特開２０１５−７２９９９７号公報Japanese Patent Laying-Open No. 2015-729997

炭化珪素半導体装置がオンしているときに、例えば負荷が短絡することによって炭化珪素半導体装置に高電圧が印加されることがある。このような場合、高電圧が印加された状態で電流が流れるので、炭化珪素半導体装置を流れる電流は飽和電流となる。このような事態に備えるために、炭化珪素半導体装置の飽和電流を小さくすることが望まれている。   When the silicon carbide semiconductor device is on, a high voltage may be applied to the silicon carbide semiconductor device, for example, due to a short circuit of the load. In such a case, since a current flows in a state where a high voltage is applied, the current flowing through the silicon carbide semiconductor device becomes a saturation current. In order to prepare for such a situation, it is desired to reduce the saturation current of the silicon carbide semiconductor device.

特許文献１の炭化珪素半導体装置では、電流分散領域の不純物濃度が濃く調整されている。このような電流分散領域は、空乏化され難い。このため、電流分散領域は、高電圧が印加されたとしても、空乏化されずに、電流経路を提供してしまう。このように、電界緩和領域と電流分散領域を組合せる技術は、高耐圧と低オン抵抗を両立することができるものの、飽和電流を小さくすることが難しいという問題がある。本明細書は、電界緩和領域と電流分散領域を備える炭化珪素半導体装置において、飽和電流を小さくする技術を提供することを目的とする。   In the silicon carbide semiconductor device of Patent Document 1, the impurity concentration in the current dispersion region is adjusted to be high. Such a current distribution region is not easily depleted. For this reason, even if a high voltage is applied, the current distribution region is not depleted and provides a current path. As described above, although the technique of combining the electric field relaxation region and the current dispersion region can achieve both high withstand voltage and low on-resistance, there is a problem that it is difficult to reduce the saturation current. An object of the present specification is to provide a technique for reducing a saturation current in a silicon carbide semiconductor device including an electric field relaxation region and a current dispersion region.

本明細書で開示する半導体装置の一実施形態は、炭化珪素の半導体基板及び半導体基板の上面から深部に向けて伸びるトレンチゲートを備える。半導体基板は、第１導電型のドリフト領域、第２導電型の電界緩和領域、第１導電型の電流分散領域、第２導電型のボディ領域及び第１導電型のソース領域を有する。電界緩和領域は、ドリフト領域上に設けられており、トレンチゲートの底面を覆うように設けられている。電流分散領域は、電界緩和領域上に設けられており、トレンチゲートの側面とドリフト領域に接しており、ドリフト領域よりも高濃度である。ボディ領域は、電流分散領域上に設けられており、トレンチゲートの側面に接する。ソース領域は、ボディ領域上に設けられており、トレンチゲートの側面に接しており、ボディ領域によって電流分散領域から隔てられている。電界緩和領域が、ボディ領域に短絡するように構成されている。   One embodiment of a semiconductor device disclosed in the present specification includes a silicon carbide semiconductor substrate and a trench gate extending from an upper surface of the semiconductor substrate toward a deep portion. The semiconductor substrate has a first conductivity type drift region, a second conductivity type electric field relaxation region, a first conductivity type current distribution region, a second conductivity type body region, and a first conductivity type source region. The electric field relaxation region is provided on the drift region and is provided so as to cover the bottom surface of the trench gate. The current distribution region is provided on the electric field relaxation region, is in contact with the side surface of the trench gate and the drift region, and has a higher concentration than the drift region. The body region is provided on the current distribution region and contacts the side surface of the trench gate. The source region is provided on the body region, is in contact with the side surface of the trench gate, and is separated from the current distribution region by the body region. The electric field relaxation region is configured to be short-circuited to the body region.

上記実施形態の炭化珪素半導体装置では、電界緩和領域がボディ領域に短絡するように構成されているので、高電圧が印加されたときに、電界緩和領域と電流分散領域のｐｎ接合面から電流分散領域内に向けて空乏層が良好に伸展することができる。これにより、上記実施形態の炭化珪素半導体装置では、高電圧が印加されたときに、電流分散領域の電流経路が狭められ、飽和電流が小さくなる。   In the silicon carbide semiconductor device of the above embodiment, since the electric field relaxation region is configured to be short-circuited to the body region, when a high voltage is applied, the current dispersion from the pn junction surface of the electric field relaxation region and the current dispersion region The depletion layer can extend well into the region. Thereby, in the silicon carbide semiconductor device of the said embodiment, when a high voltage is applied, the current path of a current dispersion area | region is narrowed and a saturation current becomes small.

実施例の半導体装置の要部断面図を模式的に示しており、図３，４，５のI-I線に対応した断面図である。FIG. 6 is a schematic cross-sectional view of a main part of the semiconductor device of the example, corresponding to the II line in FIGS. 3, 4, and 5. 実施例の半導体装置の要部断面図を模式的に示しており、図３，４，５のII-II線に対応した断面図である。FIG. 3 is a schematic cross-sectional view of a main part of the semiconductor device of the example, corresponding to the II-II line of FIGS. 実施例の半導体装置の要部断面図を模式的に示しており、図１，２のIII-III線に対応した断面図である。FIG. 3 schematically illustrates a cross-sectional view of a main part of a semiconductor device according to an embodiment, corresponding to a line III-III in FIGS. 実施例の半導体装置の要部断面図を模式的に示しており、図１，２のIV-IV線に対応した断面図である。FIG. 4 schematically illustrates a cross-sectional view of a main part of a semiconductor device according to an embodiment, corresponding to a line IV-IV in FIGS. 実施例の半導体装置の要部断面図を模式的に示しており、図１，２のV-V線に対応した断面図である。FIG. 5 schematically shows a cross-sectional view of a main part of the semiconductor device of the example, corresponding to the VV line of FIGS. 実施例の半導体装置の要部断面図を模式的に示しており、電界緩和領域と電流分散領域とボディ領域の積層部分の拡大図である。The principal part sectional drawing of the semiconductor device of an Example is shown typically, and is an enlarged view of the lamination | stacking part of an electric field relaxation area | region, a current dispersion area | region, and a body area | region. 変形例の半導体装置の要部断面図を模式的に示す。The principal part sectional drawing of the semiconductor device of a modification is typically shown. 変形例の半導体装置の要部断面図を模式的に示す。The principal part sectional drawing of the semiconductor device of a modification is typically shown. 変形例の半導体装置の要部断面図を模式的に示す。The principal part sectional drawing of the semiconductor device of a modification is typically shown. 実施例の半導体装置の製造過程の要部断面図を模式的に示す。The principal part sectional drawing of the manufacturing process of the semiconductor device of an Example is shown typically. 実施例の半導体装置の製造過程の要部断面図を模式的に示す。The principal part sectional drawing of the manufacturing process of the semiconductor device of an Example is shown typically. 実施例の半導体装置の製造過程の要部断面図を模式的に示す。The principal part sectional drawing of the manufacturing process of the semiconductor device of an Example is shown typically. 実施例の半導体装置の製造過程の要部断面図を模式的に示す。The principal part sectional drawing of the manufacturing process of the semiconductor device of an Example is shown typically. 実施例の半導体装置の製造過程の要部断面図を模式的に示す。The principal part sectional drawing of the manufacturing process of the semiconductor device of an Example is shown typically. 実施例の半導体装置の製造過程の要部断面図を模式的に示す。The principal part sectional drawing of the manufacturing process of the semiconductor device of an Example is shown typically.

以下、本明細書で開示される技術の特徴を整理する。なお、以下に記す事項は、各々単独で技術的な有用性を有している。   The technical features disclosed in this specification will be summarized below. The items described below have technical usefulness independently.

本明細書で開示する炭化珪素半導体装置としては、ＭＯＳＦＥＴ（Metal Oxide Semiconductor Field Effect Transistor）及びＩＧＢＴ（Insulated Gate Bipolar Transistor）が例示される。これらの炭化珪素半導体装置の一実施形態は、炭化珪素の半導体基板及び半導体基板の上面から深部に向けて伸びるトレンチゲートを備えていてもよい。これら炭化珪素半導体装置の一実施形態は、典型的には縦型であり、半導体基板の上面及び下面の各々に一対の主電極を備えていてもよい。半導体基板は、第１導電型のドリフト領域、第２導電型の電界緩和領域、第１導電型の電流分散領域、第２導電型のボディ領域及び第１導電型のソース領域を有していてもよい。電界緩和領域は、ドリフト領域上に設けられており、トレンチゲートの底面を覆うように設けられている。電流分散領域は、電界緩和領域上に設けられており、トレンチゲートの側面とドリフト領域に接しており、ドリフト領域よりも高濃度である。ボディ領域は、電流分散領域上に設けられており、トレンチゲートの側面に接する。ソース領域は、ボディ領域上に設けられており、トレンチゲートの側面に接しており、ボディ領域によって電流分散領域から隔てられている。電界緩和領域が、ボディ領域に短絡するように構成されている。   Examples of the silicon carbide semiconductor device disclosed in this specification include a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor). One embodiment of these silicon carbide semiconductor devices may include a silicon carbide semiconductor substrate and a trench gate extending from the upper surface of the semiconductor substrate toward a deep portion. One embodiment of these silicon carbide semiconductor devices is typically a vertical type, and may include a pair of main electrodes on each of an upper surface and a lower surface of a semiconductor substrate. The semiconductor substrate has a first conductivity type drift region, a second conductivity type electric field relaxation region, a first conductivity type current spreading region, a second conductivity type body region, and a first conductivity type source region. Also good. The electric field relaxation region is provided on the drift region and is provided so as to cover the bottom surface of the trench gate. The current distribution region is provided on the electric field relaxation region, is in contact with the side surface of the trench gate and the drift region, and has a higher concentration than the drift region. The body region is provided on the current distribution region and contacts the side surface of the trench gate. The source region is provided on the body region, is in contact with the side surface of the trench gate, and is separated from the current distribution region by the body region. The electric field relaxation region is configured to be short-circuited to the body region.

電界緩和領域と電流分散領域とボディ領域は、トレンチゲートの側方において、半導体基板の厚み方向に沿って積層していてもよい。この場合、電流分散領域の厚みが一定であるのが望ましい。この炭化珪素半導体装置では、積層部分において、厚み一定の電流分散領域が電界緩和領域とボディ領域によって挟まれる。このため、炭化珪素半導体装置に高電圧が印加されたときに、積層部分において、電流分散領域の電流経路が上下から空乏層によって狭められるので、飽和電流が小さくなる。   The electric field relaxation region, the current distribution region, and the body region may be stacked along the thickness direction of the semiconductor substrate on the side of the trench gate. In this case, it is desirable that the thickness of the current distribution region is constant. In this silicon carbide semiconductor device, a constant current distribution region is sandwiched between the electric field relaxation region and the body region in the stacked portion. For this reason, when a high voltage is applied to the silicon carbide semiconductor device, the current path in the current distribution region is narrowed from above and below by the depletion layer in the stacked portion, so that the saturation current is reduced.

電界緩和領域と電流分散領域とボディ領域の積層部分を有する炭化珪素半導体装置では、電流分散領域の厚みが、トレンチゲートの側面に直交する方向において電流分散領域と電界緩和領域が接する長さよりも小さいのが望ましい。この形態によると、炭化珪素半導体装置に高電圧が印加されたときに、積層部分において、電流分散領域の電流経路が空乏層によって良好に狭められるので、飽和電流が小さくなる。   In a silicon carbide semiconductor device having a laminated portion of an electric field relaxation region, a current distribution region, and a body region, the thickness of the current distribution region is smaller than the length of contact between the current distribution region and the electric field relaxation region in the direction perpendicular to the side surface of the trench gate. Is desirable. According to this embodiment, when a high voltage is applied to the silicon carbide semiconductor device, the current path in the current distribution region is satisfactorily narrowed by the depletion layer in the stacked portion, so that the saturation current is reduced.

電流分散領域は、隣り合うトレンチゲートの間において離間していてもよい。この場合、ドリフト領域とボディ領域が、電流分散領域の離間部分を介して接するのが望ましい。さらに、電流分散領域の全範囲が、電界緩和領域とボディ領域によって挟まれているのが望ましい。この形態によると、電流分散領域の電気抵抗値が高くなるので、飽和電流が小さくなる。   The current distribution regions may be separated between adjacent trench gates. In this case, it is desirable that the drift region and the body region are in contact with each other through a separated portion of the current dispersion region. Furthermore, it is desirable that the entire range of the current distribution region is sandwiched between the electric field relaxation region and the body region. According to this embodiment, since the electric resistance value in the current dispersion region is increased, the saturation current is decreased.

トレンチゲートは、半導体基板の上面に直交する方向から観測したときに、一方向に沿って伸びていてもよい。この場合、電界緩和領域とボディ領域は、トレンチゲートの長手方向の端部において、接するように構成されているのが望ましい。この形態によると、電界緩和領域とボディ領域が直接的に接することで、電界緩和領域とボディ領域が短絡する。   The trench gate may extend along one direction when observed from a direction orthogonal to the upper surface of the semiconductor substrate. In this case, it is desirable that the electric field relaxation region and the body region are configured to contact each other at the end in the longitudinal direction of the trench gate. According to this configuration, the electric field relaxation region and the body region are in direct contact with each other, so that the electric field relaxation region and the body region are short-circuited.

電界緩和領域とボディ領域はさらに、トレンチゲートの長手方向の両端部の間において、複数箇所で接するように構成されているのが望ましい。この形態によると、電界緩和領域の電位は、トレンチゲートの長手方向の広い範囲でボディ領域の電位に安定することができる。   It is desirable that the electric field relaxation region and the body region are further configured to be in contact at a plurality of locations between both ends in the longitudinal direction of the trench gate. According to this embodiment, the electric potential of the electric field relaxation region can be stabilized to the electric potential of the body region in a wide range in the longitudinal direction of the trench gate.

図１に示されるように、炭化珪素半導体装置１は、ＭＯＳＦＥＴと称されるパワー半導体素子であり、半導体基板１０、半導体基板１０の下面を被覆するドレイン電極２２、半導体基板１０の上面を被覆するソース電極２４及び半導体基板１０の上層部に設けられているトレンチゲート３０を備える。トレンチゲート３０は、半導体基板１０の上面に対して直交する方向から観測したときに、ストライプ状に配置されている（図３，４，５参照）。   As shown in FIG. 1, silicon carbide semiconductor device 1 is a power semiconductor element called MOSFET, and covers semiconductor substrate 10, drain electrode 22 covering the lower surface of semiconductor substrate 10, and upper surface of semiconductor substrate 10. The source electrode 24 and the trench gate 30 provided in the upper layer part of the semiconductor substrate 10 are provided. The trench gates 30 are arranged in a stripe shape when observed from a direction orthogonal to the upper surface of the semiconductor substrate 10 (see FIGS. 3, 4, and 5).

半導体基板１０は、炭化珪素（ＳｉＣ）を材料とする基板であり、ｎ+型のドレイン領域１１、ｎ-型のドリフト領域１２、ｐ+型の電界緩和領域１３、ｎ+型の電流分散領域１４、ｐ型のボディ領域１５、ｐ+型のボディコンタクト領域１６及びｎ+型のソース領域１７を有する。 The semiconductor substrate 10 is a substrate made of silicon carbide (SiC), and includes an n + type drain region 11, an n − type drift region 12, a p + type electric field relaxation region 13, and an n + type current distribution region. 14 includes a p-type body region 15, a p + -type body contact region 16, and an n + -type source region 17.

ドレイン領域１１は、半導体基板１０の下層部に配置されており、半導体基板１０の下面に露出する。ドレイン領域１１は、後述するドリフト領域１２がエピタキシャル成長するための下地基板でもある。ドレイン領域１１は、半導体基板１０の下面を被膜するドレイン電極２２にオーミック接触する。一例では、ドレイン領域１１の不純物濃度は約１×１０19ｃｍ-3以上であるのが望ましい。 The drain region 11 is disposed in the lower layer portion of the semiconductor substrate 10 and is exposed on the lower surface of the semiconductor substrate 10. The drain region 11 is also a base substrate for epitaxial growth of a drift region 12 described later. The drain region 11 is in ohmic contact with the drain electrode 22 that coats the lower surface of the semiconductor substrate 10. In one example, the drain region 11 preferably has an impurity concentration of about 1 × 10 19 cm −3 or more.

ドリフト領域１２は、ドレイン領域１１上に設けられている。ドリフト領域１２は、エピタキシャル成長技術を利用して、ドレイン領域１１の表面から結晶成長して形成される。ドリフト領域１２の不純物濃度は、半導体基板１０の厚み方向に一定である。一例では、ドリフト領域１２の不純物濃度は約１×１０15〜５×１０16ｃｍ-3であるのが望ましい。 The drift region 12 is provided on the drain region 11. The drift region 12 is formed by crystal growth from the surface of the drain region 11 using an epitaxial growth technique. The impurity concentration of the drift region 12 is constant in the thickness direction of the semiconductor substrate 10. In one example, the impurity concentration of the drift region 12 is desirably about 1 × 10 15 to 5 × 10 16 cm −3 .

電界緩和領域１３は、ドリフト領域１２上に設けられており、トレンチゲート３０の底面を覆うように設けられている（図３参照）。より詳細には、電界緩和領域１３は、トレンチゲート３０の底面の全範囲に接するとともに、トレンチゲート３０の底面から側方にも突出してトレンチゲート３０の側面の一部にも接するように設けられている。電界緩和領域１３は、トレンチゲート３０とドリフト領域１２を隔てるように構成されている。電界緩和領域１３は、イオン注入技術を利用して、ドリフト領域１２の表層部にアルミニウムを導入して形成される。一例では、電界緩和領域１３のドーズ量は約５×１０11〜５×１０12ｃｍ-2であり、ピーク濃度が約１×１０17〜５×１０18ｃｍ-3であるのが望ましい。 The electric field relaxation region 13 is provided on the drift region 12, and is provided so as to cover the bottom surface of the trench gate 30 (see FIG. 3). More specifically, the electric field relaxation region 13 is provided so as to be in contact with the entire range of the bottom surface of the trench gate 30 and to protrude sideways from the bottom surface of the trench gate 30 so as to be in contact with a part of the side surface of the trench gate 30. ing. The electric field relaxation region 13 is configured to separate the trench gate 30 and the drift region 12. The electric field relaxation region 13 is formed by introducing aluminum into the surface layer portion of the drift region 12 using an ion implantation technique. In one example, it is desirable that the dose amount of the electric field relaxation region 13 is about 5 × 10 11 to 5 × 10 12 cm −2 and the peak concentration is about 1 × 10 17 to 5 × 10 18 cm −3 .

電流分散領域１４は、ドリフト領域１２及び電界緩和領域１３上に設けられている。電流分散領域１４は、トレンチゲート３０の側面とドリフト領域１２の双方に接するように構成されている。電流分散領域１４は、隣り合うトレンチゲート３０の間を連続して延びており、厚みが一定である。電流分散領域１４の不純物濃度は、ドリフト領域１２の不純物濃度よりも濃い。電流分散領域１４は、イオン注入技術を利用して、電界緩和領域１３及びドリフト領域１２の表層部に窒素又はリンを導入して形成される。一例では、電流分散領域１４のドーズ量は約１×１０10〜１×１０12ｃｍ-2であり、ピーク濃度が約１×１０16〜１×１０18ｃｍ-3であるのが望ましい。一例では、電流分散領域１４の厚みは約０．５〜１．５μｍであるのが望ましい。 The current distribution region 14 is provided on the drift region 12 and the electric field relaxation region 13. The current distribution region 14 is configured to contact both the side surface of the trench gate 30 and the drift region 12. The current distribution region 14 extends continuously between adjacent trench gates 30 and has a constant thickness. The impurity concentration of the current dispersion region 14 is higher than the impurity concentration of the drift region 12. The current distribution region 14 is formed by introducing nitrogen or phosphorus into the surface layer portions of the electric field relaxation region 13 and the drift region 12 using an ion implantation technique. In one example, the dose amount of the current dispersion region 14 is preferably about 1 × 10 10 to 1 × 10 12 cm −2 and the peak concentration is preferably about 1 × 10 16 to 1 × 10 18 cm −3 . In one example, the thickness of the current spreading region 14 is desirably about 0.5 to 1.5 μm.

電流分散領域１４は、トレンチゲート３０の長手方向の端部近傍に形成されていない（図４参照）。このため、電界緩和領域１３は、トレンチゲート３０の長手方向の端部において、ボディ領域１５に接触しており、ボディ領域１５に短絡するように構成されている（図２参照）。   The current distribution region 14 is not formed near the end in the longitudinal direction of the trench gate 30 (see FIG. 4). For this reason, the electric field relaxation region 13 is in contact with the body region 15 at the end in the longitudinal direction of the trench gate 30 and is configured to be short-circuited to the body region 15 (see FIG. 2).

ボディ領域１５は、電流分散領域１４上に設けられており、半導体基板１０の上層部に配置されている。ボディ領域１５は、トレンチゲート３０の側面に接する。ボディ領域１５は、エピタキシャル成長技術を利用して、電流分散領域１４の表面から結晶成長して形成される。一例では、ボディ領域１５の不純物濃度は、半導体基板１０の厚み方向に一定である。一例では、ボディ領域１５の不純物濃度は約１×１０16〜１×１０18ｃｍ-3であるのが望ましい。 The body region 15 is provided on the current distribution region 14 and is disposed in the upper layer portion of the semiconductor substrate 10. Body region 15 is in contact with the side surface of trench gate 30. The body region 15 is formed by crystal growth from the surface of the current distribution region 14 using an epitaxial growth technique. In one example, the impurity concentration of the body region 15 is constant in the thickness direction of the semiconductor substrate 10. In one example, the impurity concentration of the body region 15 is desirably about 1 × 10 16 to 1 × 10 18 cm −3 .

ボディコンタクト領域１６は、ボディ領域１５上に設けられており、半導体基板１０の上層部に配置されており、半導体基板１０の上面に露出する。ボディコンタクト領域１６は、イオン注入技術を利用して、半導体基板１０の上層部にアルミニウムを導入して形成される。ボディコンタクト領域１６は、半導体基板１０の上面を被膜するソース電極２４にオーミック接触する。一例では、ボディコンタクト領域１６のドーズ量は約１×１０14〜１×１０15ｃｍ-2であり、ピーク濃度が約１×１０19〜２×１０20ｃｍ-3であるのが望ましい。 The body contact region 16 is provided on the body region 15, is disposed on the upper layer portion of the semiconductor substrate 10, and is exposed on the upper surface of the semiconductor substrate 10. The body contact region 16 is formed by introducing aluminum into the upper layer portion of the semiconductor substrate 10 using an ion implantation technique. The body contact region 16 is in ohmic contact with the source electrode 24 that coats the upper surface of the semiconductor substrate 10. In one example, the dose of the body contact region 16 is preferably about 1 × 10 14 to 1 × 10 15 cm −2 and the peak concentration is preferably about 1 × 10 19 to 2 × 10 20 cm −3 .

ソース領域１７は、ボディ領域１５上に設けられており、半導体基板１０の上層部に配置されており、半導体基板１０の上面に露出する。ソース領域１７は、ボディ領域１５によってドリフト領域１２から隔てられている。ソース領域１７は、トレンチゲート３０の側面に接する。ソース領域１７は、トレンチゲート３０の長手方向の端部近傍に形成されていない（図５参照）。換言すると、トレンチゲート３０のうちのソース領域１７が接していない部分を端部という。このように、トレンチゲート３０の端部にソース領域１７が接していないので、トレンチゲート３０の端部においてソース領域１７からゲート電極３４に電子が流入するリークが抑えられる。ソース領域１７は、イオン注入技術を利用して、半導体基板１０の上層部に窒素又はリンを導入して形成される。ソース領域１７は、半導体基板１０の上面を被膜するソース電極２４にオーミック接触する。一例では、ソース領域１７のドーズ量は約１×１０14〜５×１０15ｃｍ-2であり、ピーク濃度が約１×１０19〜５×１０20ｃｍ-3であるのが望ましい。 The source region 17 is provided on the body region 15, is disposed on the upper layer portion of the semiconductor substrate 10, and is exposed on the upper surface of the semiconductor substrate 10. Source region 17 is separated from drift region 12 by body region 15. The source region 17 is in contact with the side surface of the trench gate 30. The source region 17 is not formed near the end in the longitudinal direction of the trench gate 30 (see FIG. 5). In other words, a portion of the trench gate 30 where the source region 17 is not in contact is referred to as an end portion. Thus, since the source region 17 is not in contact with the end portion of the trench gate 30, leakage of electrons flowing from the source region 17 into the gate electrode 34 at the end portion of the trench gate 30 is suppressed. The source region 17 is formed by introducing nitrogen or phosphorus into the upper layer portion of the semiconductor substrate 10 using an ion implantation technique. The source region 17 is in ohmic contact with the source electrode 24 that coats the upper surface of the semiconductor substrate 10. In one example, it is desirable that the dose amount of the source region 17 is about 1 × 10 14 to 5 × 10 15 cm −2 and the peak concentration is about 1 × 10 19 to 5 × 10 20 cm −3 .

トレンチゲート３０は、半導体基板１０の上面から深部に向けて伸びており、ゲート絶縁膜３２及びゲート電極３４を有する。トレンチゲート３０は、ソース領域１７、ボディ領域１５及び電流分散領域１４を貫通して電界緩和領域１３に達する。ソース領域１７、ボディ領域１５及び電流分散領域１４はトレンチゲート３０の側面に接しており、電界緩和領域１３はトレンチゲート３０の底面及び側面に接する。ゲート絶縁膜３２は、酸化シリコンである。ゲート電極３４は、ゲート絶縁膜３２で被覆されており、不純物を含むポリシリコンである。   The trench gate 30 extends from the upper surface of the semiconductor substrate 10 toward a deep portion, and includes a gate insulating film 32 and a gate electrode 34. The trench gate 30 passes through the source region 17, the body region 15, and the current distribution region 14 and reaches the electric field relaxation region 13. The source region 17, the body region 15, and the current distribution region 14 are in contact with the side surface of the trench gate 30, and the electric field relaxation region 13 is in contact with the bottom surface and the side surface of the trench gate 30. The gate insulating film 32 is silicon oxide. The gate electrode 34 is covered with a gate insulating film 32 and is polysilicon containing impurities.

次に、図１を参照し、炭化珪素半導体装置１の動作を説明する。ドレイン電極２２に正電圧が印加され、ソース電極２４が接地され、トレンチゲート３０のゲート電極３４が接地されていると、炭化珪素半導体装置１はオフである。炭化珪素半導体装置１では、電界緩和領域１３がトレンチゲート３０の底面を覆うように設けられている。さらに、電界緩和領域１３がボディ領域１５に短絡しているので、電界緩和領域１３が接する部分のトレンチゲート３０のゲート絶縁膜３２に電界が加わらない。炭化珪素半導体装置１は、トレンチゲート３０の底面において電界集中が緩和され、高い耐圧を有することができる。   Next, the operation of silicon carbide semiconductor device 1 will be described with reference to FIG. When a positive voltage is applied to drain electrode 22, source electrode 24 is grounded, and gate electrode 34 of trench gate 30 is grounded, silicon carbide semiconductor device 1 is off. In silicon carbide semiconductor device 1, electric field relaxation region 13 is provided so as to cover the bottom surface of trench gate 30. Furthermore, since the electric field relaxation region 13 is short-circuited to the body region 15, no electric field is applied to the gate insulating film 32 of the trench gate 30 in contact with the electric field relaxation region 13. Silicon carbide semiconductor device 1 has a high breakdown voltage because electric field concentration is reduced at the bottom surface of trench gate 30.

ドレイン電極２２に正電圧が印加され、ソース電極２４が接地され、トレンチゲート３０のゲート電極３４にソース電極２４よりも正となる電圧が印加されていると、炭化珪素半導体装置１はオンである。このとき、ソース領域１７と電流分散領域１４を隔てるボディ領域１５のうちのトレンチゲート３０の側面に対向する部分に反転層が形成される。ソース領域１７から供給される電子は、その反転層を経由して電流分散領域１４に達する。電流分散領域１４に達した電子は、電流分散領域１４を経由してドリフト領域１２に流れる。このように、炭化珪素半導体装置１では、トレンチゲート３０の底面を覆うように電界緩和領域１３が設けられていても、電界緩和領域１３を迂回するように電流分散領域１４を介して電流が流れるので、チャネル抵抗が低く抑えられる。   When a positive voltage is applied to drain electrode 22, source electrode 24 is grounded, and a voltage that is more positive than source electrode 24 is applied to gate electrode 34 of trench gate 30, silicon carbide semiconductor device 1 is on. . At this time, an inversion layer is formed in a portion of the body region 15 that separates the source region 17 and the current spreading region 14 from the side facing the side surface of the trench gate 30. Electrons supplied from the source region 17 reach the current distribution region 14 via the inversion layer. The electrons that have reached the current distribution region 14 flow to the drift region 12 via the current distribution region 14. Thus, in silicon carbide semiconductor device 1, even if electric field relaxation region 13 is provided so as to cover the bottom surface of trench gate 30, a current flows through current distribution region 14 so as to bypass electric field relaxation region 13. Therefore, the channel resistance can be kept low.

例えば、炭化珪素半導体装置１がオンしているときに、負荷が短絡することによって炭化珪素半導体装置１に高電圧が印加されることがある。このような場合、炭化珪素半導体装置１では、電界緩和領域１３がボディ領域１５に短絡しているので、電界緩和領域１３の電位はボディ領域１５の電位（接地電位）に安定している。このため、炭化珪素半導体装置１に高電圧が印加されたときに、電界緩和領域１３と電流分散領域１４のｐｎ接合から電流分散領域１４内に向けて空乏層が良好に伸展することができる。例えば、電界緩和領域１３の電位がフローティングの場合、電界緩和領域１３の電位が不安定であり、炭化珪素半導体装置１に高電圧が印加されたとしても、電界緩和領域１３と電流分散領域１４のｐｎ接合から電流分散領域１４内に向けて伸びる空乏層幅が小さくなる。一方、本実施例の炭化珪素半導体装置１では、高電圧が印加されたときに、電流分散領域１４の電流経路が空乏層によって狭められ、飽和電流が小さくなる。   For example, when the silicon carbide semiconductor device 1 is on, a high voltage may be applied to the silicon carbide semiconductor device 1 due to a short circuit of the load. In such a case, in silicon carbide semiconductor device 1, since electric field relaxation region 13 is short-circuited to body region 15, the potential of electric field relaxation region 13 is stable to the potential of body region 15 (ground potential). For this reason, when a high voltage is applied to silicon carbide semiconductor device 1, the depletion layer can be favorably extended from the pn junction of electric field relaxation region 13 and current distribution region 14 into current distribution region 14. For example, when the electric potential of the electric field relaxation region 13 is floating, the electric potential of the electric field relaxation region 13 is unstable, and even if a high voltage is applied to the silicon carbide semiconductor device 1, the electric field relaxation region 13 and the current spreading region 14 The width of the depletion layer extending from the pn junction toward the current distribution region 14 is reduced. On the other hand, in the silicon carbide semiconductor device 1 of the present embodiment, when a high voltage is applied, the current path of the current distribution region 14 is narrowed by the depletion layer, and the saturation current is reduced.

図６に示されるように、炭化珪素半導体装置１では、トレンチゲート３０の側方において、電界緩和領域１３と電流分散領域１４とボディ領域１５が積層した積層部分が形成されている。換言すると、電流分散領域１４は、電界緩和領域１３とボディ領域１５によって挟まれている。この積層部分では、電流分散領域１４の厚みを１４Ｔとし、トレンチゲート３０の側面に直交する方向（紙面左右方向）において電流分散領域１４と電界緩和領域１３が接する長さを１４Ｌとすると、厚み１４Ｔが長さ１４Ｌよりも小さい関係が成立する。このような積層部分では、炭化珪素半導体装置１に高電圧が印加されたときに、電流分散領域１４の電流経路が上下から伸びる空乏層によって良好に狭められ、飽和電流が小さくなる。   As shown in FIG. 6, in silicon carbide semiconductor device 1, a laminated portion in which electric field relaxation region 13, current spreading region 14, and body region 15 are laminated is formed on the side of trench gate 30. In other words, the current spreading region 14 is sandwiched between the electric field relaxation region 13 and the body region 15. In this laminated portion, when the thickness of the current distribution region 14 is 14T, and the length where the current distribution region 14 and the electric field relaxation region 13 are in contact with each other in the direction orthogonal to the side surface of the trench gate 30 (left and right in the drawing) is 14L. Is smaller than the length 14L. In such a laminated portion, when a high voltage is applied to the silicon carbide semiconductor device 1, the current path of the current distribution region 14 is satisfactorily narrowed by the depletion layer extending from above and below, and the saturation current is reduced.

図７に示されるように、電界緩和領域１３は、トレンチゲート３０の長手方向に沿って、複数箇所で電流分散領域１４から露出するように構成されているのが望ましい。換言すると、電界緩和領域１３とボディ領域１５は、トレンチゲート３０の長手方向の両端部の間において、複数箇所で接するように構成されているのが望ましい。この形態によると、電界緩和領域１３の電位は、トレンチゲート３０の長手方向の広い範囲でボディ領域１５の電位に安定することができる。これにより、上記した電界緩和領域１３の電界緩和機能及び空乏層伸展機能がトレンチゲート３０の長手方向の広い範囲で発揮される。   As shown in FIG. 7, the electric field relaxation region 13 is desirably configured to be exposed from the current distribution region 14 at a plurality of locations along the longitudinal direction of the trench gate 30. In other words, it is desirable that the electric field relaxation region 13 and the body region 15 are configured to be in contact with each other at a plurality of positions between both end portions in the longitudinal direction of the trench gate 30. According to this embodiment, the potential of the electric field relaxation region 13 can be stabilized to the potential of the body region 15 in a wide range in the longitudinal direction of the trench gate 30. Thereby, the above-described electric field relaxation function and depletion layer extension function of the electric field relaxation region 13 are exhibited in a wide range in the longitudinal direction of the trench gate 30.

図８に示されるように、電流分散領域１４は、隣り合うトレンチゲート３０の間において離間していてもよい。この場合、ドリフト領域１２とボディ領域１５が、電流分散領域１４の離間部分を介して接する。この形態によると、電流分散領域１４の電流経路の電気抵抗が高くなるので、炭化珪素半導体装置１の飽和電流がさらに小さくなる。   As shown in FIG. 8, the current distribution regions 14 may be separated between adjacent trench gates 30. In this case, the drift region 12 and the body region 15 are in contact with each other through the separated portion of the current spreading region 14. According to this embodiment, since the electric resistance of the current path in current distribution region 14 is increased, the saturation current of silicon carbide semiconductor device 1 is further reduced.

図９に示されるように、電流分散領域１４は、半導体基板１０の上面に対して直交する方向から観測したときに、電界緩和領域１３の範囲内に収まるのが望ましい。換言すると、電流分散領域１４の全範囲が、電界緩和領域１３とボディ領域１５によって挟まれているのが望ましい。この形態によると、電流分散領域１４の電流経路の電気抵抗がさらに高くなるので、炭化珪素半導体装置１の飽和電流がさらに小さくなる。   As shown in FIG. 9, the current distribution region 14 is preferably within the range of the electric field relaxation region 13 when observed from a direction orthogonal to the upper surface of the semiconductor substrate 10. In other words, it is desirable that the entire range of the current spreading region 14 is sandwiched between the electric field relaxation region 13 and the body region 15. According to this embodiment, since the electric resistance of the current path in current distribution region 14 is further increased, the saturation current of silicon carbide semiconductor device 1 is further decreased.

次に、実施例の炭化珪素半導体装置１の製造方法を説明する。まず、図１０Ａに示されるように、ドレイン領域１１とドリフト領域１２が積層した半導体基板を準備する。この半導体基板は、エピタキシャル成長技術を利用して、ドレイン領域１１からドリフト領域１２を結晶成長して形成される。   Next, the manufacturing method of the silicon carbide semiconductor device 1 of an Example is demonstrated. First, as shown in FIG. 10A, a semiconductor substrate in which a drain region 11 and a drift region 12 are stacked is prepared. This semiconductor substrate is formed by crystal growth of the drift region 12 from the drain region 11 using an epitaxial growth technique.

次に、図１０Ｂに示されるように、イオン注入技術を利用して、ドリフト領域１２の表層部にアルミニウムを注入して電界緩和領域１３を形成する。   Next, as shown in FIG. 10B, the electric field relaxation region 13 is formed by implanting aluminum into the surface layer portion of the drift region 12 using an ion implantation technique.

次に、図１０Ｃに示されるように、イオン注入技術を利用して、ドリフト領域１２及び電界緩和領域１３の表層部に窒素を注入して電流分散領域１４を形成する。イオン注入技術に代えて、エピタキシャル成長技術を利用して、ドリフト領域１２及び電界緩和領域１３の表面から電流分散領域１４を結晶成長して形成してもよい。なお、電流分散領域１４が分断する例（図８及び図９参照）の場合、電流分散領域１４は、選択的にイオン注入することで形成されてもよく、エピタキシャル成長した後に一部をエッチングにより除去して形成されてもよい。   Next, as shown in FIG. 10C, the current distribution region 14 is formed by implanting nitrogen into the surface layer portions of the drift region 12 and the electric field relaxation region 13 using an ion implantation technique. Instead of the ion implantation technique, the current distribution region 14 may be formed by crystal growth from the surfaces of the drift region 12 and the electric field relaxation region 13 using an epitaxial growth technology. In the case where the current distribution region 14 is divided (see FIGS. 8 and 9), the current distribution region 14 may be formed by selective ion implantation, and a part thereof is removed by etching after epitaxial growth. May be formed.

次に、図１０Ｄに示されるように、エピタキシャル成長技術を利用して、電流分散領域１４の表面からボディ領域１５を結晶成長して形成する。   Next, as shown in FIG. 10D, the body region 15 is formed by crystal growth from the surface of the current distribution region 14 using an epitaxial growth technique.

次に、図１０Ｅに示されるように、イオン注入技術を利用して、ボディ領域１５の表層部にアルミニウムを注入してボディコンタクト領域１６を形成するとともに窒素を注入してソース領域１７を形成する。   Next, as shown in FIG. 10E, using the ion implantation technique, aluminum is implanted into the surface layer portion of the body region 15 to form the body contact region 16 and nitrogen is implanted to form the source region 17. .

次に、図１０Ｆに示されるように、ソース領域１７、ボディ領域１５及び電流分散領域１４を貫通して電界緩和領域１３に達するトレンチを形成する。次に、ＣＶＤ技術を利用して、そのトレンチ内にゲート絶縁膜３２を堆積する。次に、ＣＶＤ技術を利用して、ゲート電極３４をトレンチ内に充填する。最後に、半導体基板の下面にドレイン電極２２を被膜し、半導体基板の上面にソース電極２４を被膜すると、炭化珪素半導体装置１が完成する。   Next, as shown in FIG. 10F, a trench that penetrates the source region 17, the body region 15, and the current distribution region 14 and reaches the electric field relaxation region 13 is formed. Next, a gate insulating film 32 is deposited in the trench using CVD technology. Next, the gate electrode 34 is filled in the trench using the CVD technique. Finally, when drain electrode 22 is coated on the lower surface of the semiconductor substrate and source electrode 24 is coated on the upper surface of the semiconductor substrate, silicon carbide semiconductor device 1 is completed.

以上、本発明の具体例を詳細に説明したが、これらは例示に過ぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。また、本明細書または図面に説明した技術要素は、単独であるいは各種の組合せによって技術的有用性を発揮するものであり、出願時請求項記載の組合せに限定されるものではない。また、本明細書または図面に例示した技術は複数目的を同時に達成し得るものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。   Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

１：炭化珪素半導体装置
１０：半導体基板
１１：ドレイン領域
１２：ドリフト領域
１３：電界緩和領域
１４：電流分散領域
１５：ボディ領域
１６：ボディコンタクト領域
１７：ソース領域
２２：ドレイン電極
２４：ソース電極
３０：トレンチゲート
３２：ゲート絶縁膜
３４：ゲート電極 1: Silicon carbide semiconductor device 10: Semiconductor substrate 11: Drain region 12: Drift region 13: Electric field relaxation region 14: Current distribution region 15: Body region 16: Body contact region 17: Source region 22: Drain electrode 24: Source electrode 30 : Trench gate 32: Gate insulating film 34: Gate electrode

Claims (7)

炭化珪素の半導体基板と、
前記半導体基板の上面から深部に向けて伸びるトレンチゲートと、を備え、
前記半導体基板は、
第１導電型のドリフト領域と、
前記ドリフト領域上に設けられており、前記トレンチゲートの底面を覆うように設けられている第２導電型の電界緩和領域と、
前記電界緩和領域上に設けられており、前記トレンチゲートの側面と前記ドリフト領域に接しており、前記ドリフト領域よりも高濃度の第１導電型の電流分散領域と、
前記電流分散領域上に設けられており、前記トレンチゲートの前記側面に接する第２導電型のボディ領域と、
前記ボディ領域上に設けられており、前記トレンチゲートの側面に接しており、前記ボディ領域によって前記電流分散領域から隔てられている第１導電型のソース領域と、を有し、
前記電界緩和領域が、前記ボディ領域に短絡するように構成されている、炭化珪素半導体装置。 A silicon carbide semiconductor substrate;
A trench gate extending from the upper surface of the semiconductor substrate toward the deep portion, and
The semiconductor substrate is
A drift region of a first conductivity type;
A second conductivity type electric field relaxation region provided on the drift region and covering the bottom surface of the trench gate;
Provided on the electric field relaxation region, in contact with the side surface of the trench gate and the drift region, and a current distribution region of a first conductivity type having a higher concentration than the drift region;
A body region of a second conductivity type provided on the current distribution region and in contact with the side surface of the trench gate;
A first conductivity type source region provided on the body region, in contact with a side surface of the trench gate, and separated from the current distribution region by the body region;
A silicon carbide semiconductor device configured such that said electric field relaxation region is short-circuited to said body region. 前記電界緩和領域と前記電流分散領域と前記ボディ領域は、前記トレンチゲートの側方において、前記半導体基板の厚み方向に沿って積層しており、
前記電流分散領域の厚みが一定である、請求項１に記載の炭化珪素半導体装置。 The electric field relaxation region, the current distribution region, and the body region are stacked along the thickness direction of the semiconductor substrate at a side of the trench gate,
The silicon carbide semiconductor device according to claim 1, wherein the thickness of the current distribution region is constant. 前記電流分散領域の前記厚みは、前記トレンチゲートの前記側面に直交する方向において前記電流分散領域と前記電界緩和領域が接する長さよりも小さい、請求項２に記載の炭化珪素半導体装置。   3. The silicon carbide semiconductor device according to claim 2, wherein the thickness of the current distribution region is smaller than a length of contact between the current distribution region and the electric field relaxation region in a direction orthogonal to the side surface of the trench gate. 前記電流分散領域は、隣り合うトレンチゲートの間において離間しており、
前記ドリフト領域と前記ボディ領域が、前記電流分散領域の離間部分を介して接する、請求項１〜３のいずれか一項に記載の炭化珪素半導体装置。 The current spreading region is spaced between adjacent trench gates;
The silicon carbide semiconductor device according to any one of claims 1 to 3, wherein the drift region and the body region are in contact with each other through a separation portion of the current distribution region. 前記電流分散領域の全範囲が、前記電界緩和領域と前記ボディ領域によって挟まれている、請求項４に記載の炭化珪素半導体装置。   The silicon carbide semiconductor device according to claim 4, wherein the entire range of the current distribution region is sandwiched between the electric field relaxation region and the body region. 前記トレンチゲートは、前記半導体基板の前記上面に直交する方向から観測したときに、一方向に沿って伸びており、
前記電界緩和領域と前記ボディ領域は、前記トレンチゲートの長手方向の端部において、接するように構成されている、請求項１〜５のいずれか一項に記載の炭化珪素半導体装置。 The trench gate extends along one direction when observed from a direction orthogonal to the upper surface of the semiconductor substrate,
The silicon carbide semiconductor device according to claim 1, wherein the electric field relaxation region and the body region are configured to contact each other at an end portion in a longitudinal direction of the trench gate. 前記電界緩和領域と前記ボディ領域は、前記トレンチゲートの前記長手方向の両端部の間において、複数箇所で接するように構成されている、請求項６に記載の炭化珪素半導体装置。   The silicon carbide semiconductor device according to claim 6, wherein said electric field relaxation region and said body region are configured to be in contact at a plurality of locations between both ends in the longitudinal direction of said trench gate.
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