Silicon carbide semiconductor device and method for manufacturing the same
First Claim
1. A method for manufacturing a silicon carbide semiconductor device comprising the steps of:
- preparing a semiconductor substrate including a silicon carbide substrate having a first conductivity type or a second conductivity type, a first semiconductor layer made of first conductivity type silicon carbide and having an impurity concentration lower than that of the silicon carbide substrate, a second semiconductor layer made of second conductivity type silicon carbide, and a third semiconductor layer made of the first conductivity type silicon carbide, which are stacked in this order;
forming a trench in a cell region of the semiconductor substrate, the trench penetrating the second and the third semiconductor layers to reach the first semiconductor layer;
forming a fourth semiconductor layer having the first conductivity type in the trench by an epitaxial growth method in such a manner that a part of the fourth semiconductor layer disposed on a bottom of the trench is thicker than that on a sidewall of the trench;
forming an oxide film on an inner wall of the trench by a thermal oxidation method in such a manner that the oxide film includes a part for functioning as a gate oxide film, which contacts the fourth semiconductor layer, so that the fourth semiconductor layer provides a channel layer;
forming a gate electrode on a surface of the oxide film in the trench;
forming a first electrode electrically connecting to the third semiconductor layer; and
forming a second electrode electrically connecting to the silicon carbide substrate, whereinin the step of forming the oxide film, the thermal oxidation method is performed so that a position of a boundary between the first semiconductor layer and the second semiconductor layer is disposed lower than an utmost lowest position of the oxide film in the trench.
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Abstract
A silicon carbide semiconductor device includes: a semiconductor substrate having a silicon carbide substrate, a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer; a trench penetrating the second and the third semiconductor layers to reach the first semiconductor layer; a channel layer on a sidewall and a bottom of the trench; an oxide film on the channel layer; a gate electrode on the oxide film; a first electrode connecting to the third semiconductor layer; and a second electrode connecting to the silicon carbide substrate. A position of a boundary between the first semiconductor layer and the second semiconductor layer is disposed lower than an utmost lowest position of the oxide film.
15 Citations
7 Claims
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1. A method for manufacturing a silicon carbide semiconductor device comprising the steps of:
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preparing a semiconductor substrate including a silicon carbide substrate having a first conductivity type or a second conductivity type, a first semiconductor layer made of first conductivity type silicon carbide and having an impurity concentration lower than that of the silicon carbide substrate, a second semiconductor layer made of second conductivity type silicon carbide, and a third semiconductor layer made of the first conductivity type silicon carbide, which are stacked in this order; forming a trench in a cell region of the semiconductor substrate, the trench penetrating the second and the third semiconductor layers to reach the first semiconductor layer; forming a fourth semiconductor layer having the first conductivity type in the trench by an epitaxial growth method in such a manner that a part of the fourth semiconductor layer disposed on a bottom of the trench is thicker than that on a sidewall of the trench; forming an oxide film on an inner wall of the trench by a thermal oxidation method in such a manner that the oxide film includes a part for functioning as a gate oxide film, which contacts the fourth semiconductor layer, so that the fourth semiconductor layer provides a channel layer; forming a gate electrode on a surface of the oxide film in the trench; forming a first electrode electrically connecting to the third semiconductor layer; and forming a second electrode electrically connecting to the silicon carbide substrate, wherein in the step of forming the oxide film, the thermal oxidation method is performed so that a position of a boundary between the first semiconductor layer and the second semiconductor layer is disposed lower than an utmost lowest position of the oxide film in the trench. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification