A semiconductor device includes a silicon carbide semiconductor substrate, a first silicon carbide layer of a first conductivity type, a first semiconductor region of a second conductivity type, a second semiconductor region of the first conductivity type, a third semiconductor region of the second conductivity type, a gate insulating film, a gate electrode, an interlayer insulating film, a source electrode, and a drain electrode. The third semiconductor region is thicker than the second semiconductor region and a width of a side of the third semiconductor region facing the first semiconductor region is narrower than a width of a side thereof facing the source electrode.