In the above example, the case in which the amorphous silicon film is formed has been described, but the present disclosure is not limited thereto. The method of filling a recess may be applied to a case in which, for example, an amorphous germanium film or an amorphous silicon germanium film is formed. Each of the amorphous germanium film and the amorphous silicon germanium film may be, for example, a non-doped film or a doped film.

In the case of forming an amorphous germanium film, for example, a germanium source gas may be used instead of the silicon source gas. In addition, a halogen-containing germanium gas, for example, may be used instead of the halogen-containing silicon gas. Further, a hydrogenated germane gas, for example, may be used instead of the hydrogenated silane gas. Furthermore, an aminogermane-based gas, for example, may be used instead of the aminosilane-based gas.

The halogen-containing germanium gas may be, for example, a fluorine-containing germanium gas such as GeF₄, GeHF₃, GeH₂F₂, or GeH₃F, a chlorine-containing germanium gas such as GeCl₄, GeHCl₃, GeH₂Cl₂, or GeH₃Cl, or a bromine-containing germanium gas such as GeBr₄, GeHBr₃, GeH₂Br₂, or GeH₃Br. The hydrogenated germane gas may be, for example, GeH₄, Ge₂H₆, or Ge₃H₈. The aminogermane-based gas may be, for example, dimethylamino germane (DMAG), diethylamino germane (DEAG), bis(dimethylamino)germane (BDMAG), bis(diethylamino)germane (BDEAG), or tri(dimethylamino)germane (3DMAG).