A method of forming a refractory metal film doped with III or V group elements. The first process gas is supplied from a first gas source through a first gas introducing member to and through a gas supply mechanism toward a substrate within a processing vessel. The second process gas is supplied from a second gas source through a second gas introducing member to and through the gas supply mechanism toward the substrate within the processing vessel. The processing vessel is purged by evacuating the processing vessel by an evacuating mechanism, while supplying the inert gas from a third source through a third gas introducing member to and through the gas supply mechanism into the processing vessel. The supplying the first process gas and the supplying the second process gas are repeated with the supplying the purging gas being carried out between supplying the first and second gases performed so that residual gas present in the processing vessel after performing the supplying of the first and second process gases is reduced to a level of 1 to 30% based on the entire capacity of the processing vessel.