An oxide film is formed on a target substrate by CVD, in a process field to be selectively supplied with a first process gas including a silicon source gas and a second process gas including an oxidizing gas. The oxide film is formed by performing cycles each 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 the adsorption layer on the surface of the target substrate. The silicon source gas is a univalent or bivalent aminosilane gas, and each of the cycles is arranged to use a process temperature lower than that used for a trivalent aminosilane gas.