An interfacial reaction suppressing layer 12 formed between an oxide layer including a ZnO single crystal substrate 11 and a nitride layer including an InGaN semiconductor layer 13 restrains the interfacial reaction between the oxide layer and the nitride layer and formation of a reaction layer (Al2ZnO4) at the interface, which makes it possible to grow and thermally treat the InGaN semiconductor layer 13 at a high temperature. Thus, a crystal quality of the InGaN semiconductor layer 13 is improved.