Sharp interface structure of SrO film on hydrogen-terminated Si(100) is obtained by an alternate supply of Sr metal and O-2 gas. The hydrogen-terminated Si is chemically inactive, especially against oxidation. The method of alternate supply of Sr and O-2 gas makes it possible to cover Si surface with the first Sr layer for prevention of formation of Si-O bonding when O-2 gas is supplied to the substrate. Epitaxial SrO films are grown when the substrate temperature is maintained above 400 degrees C. The orientation relationship between epitaxial SrO and Si is found to be (100)SrO//(100)Si and [001]SrO//[001]Si.