A tantalum nitride film rich in tantalum atoms is formed by simultaneously introducing a raw gas consisting of a coordination compound of elemental tantalum (Ta) having a coordinated ligand of formula: N═(R, R′) (wherein, R and R′ each represents an alkyl group having 1 to 6 carbon atoms) and NH3 gas into a film-forming chamber; reacting the raw gas with the NH3 gas; forming a reduced compound having Ta—NH3 on a substrate; and introducing a hydrogen atom-containing gas into the chamber to form a tantalum nitride film rich in tantalum atoms. The resulting tantalum nitride film has a low resistance, low contents of C and N atoms, and a high compositional ratio: Ta/N, show sufficiently high adherence to Cu film and can thus be useful as a barrier film. Moreover, tantalum particles are implanted in the resulting film according to the sputtering technique to further enrich the film with tantalum.