A semiconductor device has a semiconductor layer and a substrate. The semiconductor layer constitutes at least a part of a current path, and is made of silicon carbide. The substrate has a first surface supporting the semiconductor layer, and a second surface opposite to the first surface. Further, the substrate is made of silicon carbide having a 4H type single-crystal structure. Further, the substrate has a physical property in which a ratio of a peak strength in a wavelength of around 500 nm to a peak strength in a wavelength of around 390 nm is 0.1 or smaller in photoluminescence measurement. In this way, the semiconductor device is obtained to have a low on-resistance.