A method which has a low-temperature growth step of growing a buffer layer of a ZnO-based single crystal on the substrate at a growth temperature in the range of 250° C. to 450° C. using a polar oxygen material and a metalorganic compound containing no oxygen; performing a heat treatment of the buffer layer to effect a transition of the buffer layer to a thermostable-state single crystal layer; and a high-temperature growth step of growing the ZnO-based single crystal layer on the thermostable-state single crystal layer at a growth temperature in the range of 600° C. to 900° C. using a polar oxygen material and a metalorganic compound containing no oxygen.