An insulated gate silicon carbide semiconductor device is provided having small on-resistance in a structure obtained by combining the SIT and MOSFET structures having normally-off operation. The device includes an n− semiconductor layer on an SiC n+ substrate, a p-type base region and highly doped p-region both buried in the layer, a trench from the semiconductor layer surface to the p-base region, an n+ first source region in the surface of a p-type base region at the bottom of the trench, a p-type channel region in the surface of the sidewall of the trench, one end of which contacts the first source region, a gate electrode contacting the trench-side surface of the channel region via a gate insulating film, and a source electrode contacting the trench-side surface of the gate electrode via an interlayer insulating film and contacting the exposed first source region and p-base region at the bottom of the trench.