SEMICONDUCTOR SUBSTRATE, SEMICONDUCTOR DEVICE, AND METHOD OF PRODUCING SEMICONDUCTOR SUBSTRATE

A semiconductor substrate which allows desired electrical characteristics to be more easily acquired, a semiconductor device of the same, and a method of producing the semiconductor substrate. The method of producing this semiconductor substrate is provided with: a first epitaxial layer forming step (S1) of forming a first epitaxial layer; a trench forming step (S2) of forming trenches in the first epitaxial layer; and epitaxial layer forming steps (S3, S4, S5) of forming epitaxial layers on the first epitaxial layer and inside the trenches, using a plurality of growth conditions including differing growth rates, so as to fill the trenches, and keeping the concentration of dopant taken into the epitaxial layers constant in the plurality of growth conditions.