NOVELTY - A compound semiconductor device epitaxial growth substrate comprises, sequentially, semiconductor substrate (2); substrate protective layer (3) made of a material that is different from the material of the substrate; middle layer (4) for making separation of semiconductor substrate and a compound semiconductor device layer (5) possible; and compound semiconductor device layer formed through epitaxial growth.    USE - For use in the manufacture of semiconductor device (claimed), e.g. high efficiency multijunction-type compound solar cell.    ADVANTAGE - An element layer is formed through epitaxial growth again after the substrate and the element layer that has been epitaxially grown have been separated from each other without causing an increase in the cost due to surface processing of the substrate, such as polishing or lapping, a reduction in the number of times that use is possible due to reduction in the thickness of the substrate, or a problem of reduction in the yield due to cracking of the substrate.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a manufacturing method of a compound semiconductor device epitaxial growth substrate, comprising removing a middle layer for making possible separation of a semiconductor substrate and a compound semiconductor device layer that is formed through epitaxial growth from a compound semiconductor device epitaxial growth substrate, where the semiconductor substrate, a substrate protective layer made of a material that is different from the material of the substrate, the middle layer, and the compound semiconductor device layer are sequentially layered, so that the semiconductor substrate and the compound semiconductor device layer are separated; removing the substrate protective layer through etching to expose the surface of the semiconductor substrate; and sequentially growing a substrate protective layer, middle layer and a compound semiconductor device layer on the exposed semiconductor substrate.    DESCRIPTION OF DRAWING(S) - The figure schematically shows a compound semiconductor device epitaxial growth substrate.    Semiconductor substrate (2)    Substrate protective layer (3)    Middle layer (4)    Compound semiconductor device layer (5)    Base layer (12)