A semiconductor device of an embodiment includes an n-type SiC substrate, an n-type SiC layer formed on the SiC substrate; a p-type first SiC region formed in the surface of the SiC layer and contains a p-type impurity and an n-type impurity, the p-type impurity being an element A, the n-type impurity being an element D, the element A and the element D being a combination of Al, Ga, or In and N, and/or a combination of B and P, the ratio of the concentration of the element D to the concentration of the element A in the combination(s) being higher than 0.33 but lower than 0.995, the concentration of the element A forming part of the combination(s) being not lower than 1×1017 cm−3 and not higher than 1×1022 cm−3, a first electrode, and a second electrode.