One kind of element belonging to I group or II group and one kind of binary compound including one kind of element belonging to III group and one kind of element selected from the group consisting of S, Se, Te and O are evaporated respectively by means of a vacuum vapor deposition method or molecular beam epitaxial method to produce a ternary compound semiconductor material having a low vapor pressure, and the thus produced ternary compound semiconductor material is deposited on a substrate to form a ternary compound semiconductor thin film. Particularly, when a phosphor thin film for electroluminescence emitting blue light is to be grown, an element Sr and a binary compound Ga.sub.2 S.sub.3 are respectively evaporated by the vacuum evaporation method or molecular beam epitaxial method to deposit a ternary compound semiconductor material SrGa.sub.2 S.sub.4 on a substrate, and at the same time impurity element Ce forming luminescent center is evaporated such that the ternary compound semiconductor material SrGa.sub.2 S.sub.4 is doped with the impurity element.