In a SiC power MISFET having a lateral surface of a trench formed in an upper surface of a SiC epitaxial substrate as a channel region, a silicon carbide semiconductor device having low resistance, high performance, and high reliability is realized. As a means therefor, a SiC power MISFET is formed as an island-shaped unit cell on an upper surface of an n-type SiC epitaxial substrate that is provided with a drain region on a bottom surface thereof, the SiC power MISFET including: an n-type current diffusion region that surrounds a p-type body layer contact region and an n-type source region in the indicated order in a plan view; a p-type body layer and an n-type JFET region; a trench that is formed on the body layer so as to span between the source region and the current diffusion region adjacent each other in a first direction and extends in the first direction; and a gate electrode embedded in the trench with a gate insulating film therebetween.