To provide a manufacturing method of a semiconductor device using a monitor wafer which can suppress in-batch film thickness variation in a product wafer to the utmost, and can manage precisely the thickness of the product wafer in a batch type pressure reduction CVD deposition film.

Both sides of a product wafer A are held by dummy wafers D each having the same surface area as that of the product wafer A to deposit an oxide film 202 with a batch-type CVD apparatus. Consequently, the film thickness T of the oxide film with less variation among the wafers can be yielded.