Epitaxial substrate for a semiconductor device, method for manufacturing an epitaxial substrate for a semiconductor device, and semiconductor device

Epitaxial substrate for a semiconductor device in which a group of group III nitride on a base substrate (1) of monocrystalline silicon with a (111) orientation, such that a (0001) crystal plane approximately parallel to a surface of the base substrate (1) is is formed, comprising: a first of AlN on the base substrate (1) formed Group III nitride layer (3); a second from In and at least a third group III nitride layer (5, 6), which is formed epitaxially on the second group III nitride layer, characterized in that: the first group III nitride layer (3) is a layer that contains multiple flaws (d), containing at least one kind of a columnar crystal, a particle crystal, a stalk domain, and a grain domain; an interface between the first group III nitride layer (3) and the second group III nitride layer (4) is a three-dimensional surface roughness; Bulges of the first group III nitride layer (3) have a density of 5 × 10 and a side wall of the bulges a (10-11) plane or a (10-12) plane is.