PURPOSE: To obtain a thin film having less crystal defect by forming the film by chemical reaction of chlorides produced by chemically reacting at least one of metal elements, such as mercury, cadmium and tellurium with hydrochloride.

CONSTITUTION: A reaction tube 10 is divided sequentially from a material gas supply side into a zone 14 heated by a first heater 11, a zone 15 heated by a second heater 12, and a zone 16 heated by a third heater 13, the zone 14 is heated to 750°C, the zone 15 is heated to 650°C, and the zone 16 is heated to 350°C. When (C2H5)2Te bubbled with hydrogen, (CH3)2Cd bubbled in hydrogen, and CH gas are supplied as material gases together with carrier gas H2 into the tube 10, chemical reactions occur in the respective zones, and a thin film 21 in which HgCdTe is as a main component element is formed by vapor growth on a wafer 20, and the chemical reactions are equilibrated. Accordingly, the uniformity of the compositions is improved, thereby obtaining the thin film having less crystal defect.