However, N2 can be used as the third reaction source instead, and the O2 oxidizer can be replaced by O3 or H2O. Every step of supplying a reaction source is directly followed by a purge step, which uses an inert gas such as Ar, He, or Ne, or N2 gas as a purging gas. [0061] Referring to FIG. 8, the HfCl4 gas is supplied as the first reaction source to a semiconductor substrate on which a lower elec