To prevent the occurrence of a fault in a large area in chemical vapor deposition, executed near at atmospheric pressure in a single crystal epitaxial depositing method.

Reaction gas is made to pass through an exhaust part 22 on the semiconductor wafer W of a reaction chamber 14 in a conventional method. A Venturi tube communicating with the reaction room is adjusted, and vacuum suction is carried out in the reaction chamber. Comparatively small vacuum pressure forms the flow of the reaction gas of a laminar flow going out of the reaction chamber. Thus, a possibility that particles being adhered near the exhaust part of the reaction room are loaded on gas flow, transported to the wafer and the fault of a large area occurring owing to the reduction of turbulent flow and vortex is reduced. A device 10 for executing the method is also disclosed.