Patent ID: 7541300
Filing Date: 2009-06-02
Classification: H01L,Y10S

Abstract:
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, 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.