A silicon carbide MOSFET that exhibits a high source-to-drain withstand voltage and that involves a smaller difference between gate-to-drain capacitance achieved in an activated state and gate-to-drain capacitance achieved in a deactivated state. A silicon carbide drift layer of a first conductivity type is provided on a silicon carbide substrate of a first conductivity type; a pair of base regions are provided in a surface layer portion of the silicon carbide drift layer and exhibit a second conductivity type; a pair of source regions are provided in interiors of surface layer portions of the pair of base regions and exhibit a first conductivity type; and semi-insulating regions are provided between the silicon carbide substrate and the pair of base regions.