PURPOSE: To inhibit the generation of foreign matter, and to improve yield by growing a silicon nitride film, evacuating the inside of a reaction tube up to a high vacuum and reducing the quantities of an unreacted gas and a reaction product gas left.

CONSTITUTION: A silicon nitride film is grown through a vacuum chemical vapor growth method, the supply of a reactant gas is stopped, and the inside of a reaction tube 1 is evacuated by a mechanical booster pump 4 and a rotary pump 5 to the vacuum degree of 10-3Torr. A valve A3 is closed, a valve B6 and a valve C8 are opened, and the inside of the reaction tube 1 is evacuated up to the vacuum degree of 10-6Torr or less by a turbo-molecular pump 7 and the rotary pump 5. Consequently, the degree of remaining of an unreacted gas or a reaction product gas can be reduced. Accordingly, even when oxygen in atmospheric air is mixed, the level of foreign matter on wafers can be lowered, thus improving the yield of wafers.