A silicon-containing insulating film is formed on a target substrate by CVD, in a process field to be selectively supplied with a first process gas including di-iso-propylaminosilane gas and a second process gas including an oxidizing gas or nitriding gas. The film is formed by performing a plurality of times a cycle alternately including first and second steps. The first step performs supply of the first process gas, thereby forming an adsorption layer containing silicon on a surface of the target substrate. The second performs supply of the second process gas, thereby oxidizing or nitriding the adsorption layer on the surface of the target substrate. The second step includes an excitation period of supplying the second process gas to the process field while exciting the second process gas by an exciting mechanism.