Epitaxial substrate for semiconductor element, method of manufacturing an epitaxial substrate for is a semiconductor element, and semiconductor element

Provided is an epitaxial substrate containing single-crystal silicon as the base substrate and which has excellent crystal quality and properties. An epitaxial substrate in which a group of group III nitride layers on a single crystalline (111) silicon substrate is formed so that a (0001) crystal plane is approximately parallel to a substrate surface, comprising: a first AlN on the base substrate formed group -III-nitride layer; a second of In and at least a third group-III-nitride layer that is formed on the second group III nitride layer epitaxially, wherein: the first group-III nitride layer is a layer having a plurality of voids, at least one kind of a columnar crystal, a grain crystal contain a stalk domain, and a grain domain; and an interface between the first group III nitride layer and the second Group III nitride layer is a three-dimensional surface roughness.