A semiconductor device comprising: a base layer of a first conductivity type selectively formed above a semiconductor substrate; a gate electrode formed on the base layer via the insulating film; a source layer of a second conductivity type selectively formed at a surface of the base layer at one side of the gate electrode; an channel implantation layer selectively formed at the surface of the base layer so as to be adjacent to the source layer below the gate electrode, the channel implantation layer having a higher concentration than the base layer; a RESURF layer of the second conductivity type selectively formed at the surface of the base layer at the other side of the gate electrode; and a drain layer of a second conductivity type being adjacent to the RESURF layer, a portion of the drain layer overlapping the base layer, and the drain layer having a higher concentration than the RESURF layer.