Pre-coating films are formed in a pretreatment by supplying first film-forming gases into a process chamber of a process vessel while heating the process chamber so as to form a first pre-coating film on the inner surface of the process vessel exposed to the process chamber, followed by supplying second film-forming gases into the process chamber to form a second pre-coating film on the first pre-coating film. A semiconductor wafer is loaded into the process chamber. Then, the first gases are supplied into the process chamber while heating the process chamber so as to form a first layer on the wafer, followed by supplying the second gases into the process chamber so as to form a second layer on the first layer. A silane gas is supplied into the process chamber to permit silicon material to be deposited on the surface of the second layer stacked on the first layer. Finally, the wafer having the first and second multi-film is unloaded out of the process vessel.