A semiconductor device according to an exemplary embodiment of the present invention includes an n− type epitaxial layer disposed on a first surface of a substrate; a p type region disposed on the n− type epitaxial layer, an n+ type region disposed on the p type region, a gate disposed on the n− type epitaxial layer, an oxidation film disposed on the gate, a source electrode disposed on the oxidation film and the n+ type region, and a drain electrode disposed on a second surface of the substrate. The gate includes a PN junction portion.