A semiconductor device according to embodiments includes, a SiC substrate, SiC layer, a trench having a side face and a bottom face, a first conductivity type first SiC region, a second conductivity type second SiC region between the first SiC region and the SiC substrate, a first conductivity type third SiC region between the second SiC region and the SiC substrate, a boundary between the second SiC region and the third SiC region provided at a side of the side face, the boundary including a first region, a distance between the first region and a front face of the SiC layer increasing as a distance from the side face to the first region increasing, and distance from the side face to the first region being 0 μm or more and 0.3 μm or less, a gate insulating film and gate insulating film.