Patent ID: 7399676

Claim:
A method for manufacturing a silicon carbide semiconductor device comprising the steps of: preparing a semiconductor substrate including a silicon carbide substrate and first to third semiconductor layers, wherein the first semiconductor layer made of silicon carbide and having the first conductive type and an impurity concentration lower than that of the silicon carbide substrate, the second semiconductor layer made of silicon carbide and having the second conductive type, and the third semiconductor layer made of silicon carbide and having the first conductive type are formed on the silicon carbide substrate having a first conductive type or a second conductive type in this order; forming a trench in a cell region of the semiconductor substrate so that the trench penetrates the second and the third semiconductor layers and reaches the first semiconductor layer; forming a fourth semiconductor layer having the first conductive type in the trench by an epitaxial growth method; forming an oxide film in the trench in such a manner that a part of the fourth semiconductor layer disposed on a sidewall of the trench is thermally oxidized, wherein the oxide film includes a part for functioning as a gate oxide film; 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.