A tantalum nitride film-forming method comprises the steps of introducing, into a vacuum chamber, a raw gas consisting of a coordination compound constituted by elemental Ta having a coordinated ligand represented by the general formula: N═(R,R′) (in the formula, R and R′ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms) to thus adsorb the gas on a substrate; then introducing an NH3 gas and then activated H radicals derived from a reactant gas into a vacuum chamber to thus remove the R(R′) groups bonded to the nitrogen atom present in the reaction product through cleavage, and to thus 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, can ensure sufficiently high adherence to the distributing wire-forming 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 thus further enrich the film with tantalum.