Method for making insulated-gate semiconductor element

Abstract

An insulated-gate semiconductor element with a trench structure is provided, which has a high breakdown voltage even though a silicon carbide substrate is used that is preferable to obtain a semiconductor element with favorable properties. The surface of a silicon carbide substrate is etched to form a concave portion. Then, a particle beam, for example an ion beam, is irradiated from above, and a defect layer is formed at least in a bottom surface of the concave portion. The substrate is heated in an oxidation atmosphere, and an oxide film is formed at least on a side surface and the bottom surface of the concave portion. Then, a gate electrode is formed on the oxide film. With this method, the oxide film at the bottom surface of the concave portion is thicker than the oxide film at the side surfaces of the concave portion, so that a high breakdown voltage can be ensured, even when the surface of the silicon carbide layer is a face with which a superior epitaxial layer can be attained, such as the (111) Si-face of β-SiC or the (0001) Si-face of α-SiC.

Dependencies are inferred from the claim text.