A compound semiconductor device epitaxial growth substrate, wherein a semiconductor substrate, a substrate protective layer made of a material that is different from the material of the substrate, a middle layer for making separation of the semiconductor substrate and a compound semiconductor device layer possible, and a compound semiconductor device layer that is formed through epitaxial growth are layered in this order; and a semiconductor device which uses the compound semiconductor device layer that is gained by separating the semiconductor substrate, the substrate protective layer and the middle layer from this compound semiconductor device epitaxial growth substrate; as well as manufacturing methods for these.