To provide a semiconductor device capable of reducing a gate capacitance, and preventing breakdown of a gate oxide film if a large amount of current flows. A semiconductor device according to an embodiment of the present invention includes: an epitaxial layer; a channel region formed on the epitaxial layer; a trench extending from a surface of the channel region to the epitaxial layer; a gate oxide film that covers an inner surface of the trench; a gate electrode filled into the trench; and a buried insulating film formed below the gate electrode and away from the gate oxide film.