A semiconductor stack includes a substrate made of silicon carbide, and an epi layer disposed on the substrate and made of silicon carbide. An epi principal surface, which is a principal surface opposite to the substrate, of the epi layer is a carbon surface having an off angle of 4° or smaller relative to a c-plane. In the epi principal surface, a plurality of first recessed portions having a rectangular circumferential shape in a planar view is famed. Density of a second recessed portion that is formed in the first recessed portions and is a recessed portion deeper than the first recessed portions is lower than or equal to 10 cm−2 in the epi principal surface.