Process for producing a semiconductor device having a single thermal

Abstract

A semiconductor device, which has an oxide laver with the thickness thereof being varied from portion to portion of the inner surface of a trench and can be easily produced, and a process of producing the same. An n.sup.+ type single crystal SiC substrate is formed of SiC of hexagonal system having a carbon face with a (0001) face orientation as a surface, and an n type epitaxial layer and a p type epitaxial layer are successively laminated onto the substrate. An n.sup.+ source region is provided within the p type epitaxial layer, and the trench extends through the source region and the epitaxial layer into the semiconductor substrate. The side face of the trench is almost perpendicular to the surface of the epitaxial layer with the bottom face of the trench having a plane parallel to the surface of the epitaxial layer. The thickness of a gate oxide layer, formed by thermal oxidation, on the bottom face of the trench is larger than the thickness of the gate oxide layer on the side face of the trench. A gate electrode layer is provided on the surface of the oxide layer, formed by thermal oxidation, within the trench, a source electrode layer is provided on the epitaxial layer and the source region, and a drain electrode layer is provided on the back surface of the semiconductor substrate.