Method of forming film

A method of forming a tungsten film on a surface of a target substrate having a base film by repeating a cycle plural times, the cycle including alternately supplying a tungsten chloride gas and a reducing gas for reducing the tungsten chloride gas, with a purge interposed therebetween, into a process container in which the target substrate is accommodated and that is maintained under a depressurized atmosphere, the method comprising:

• setting an integrated flow rate of the tungsten chloride gas per one cycle to be substantially constant while the tungsten film is formed on the target substrate;
• and
• shortening a time of the cycle while increasing a supply flow rate of the tungsten chloride gas within a range where a ratio of a thickness of the base film etched by repeating the cycle the plural times to a thickness of the base film before repeating the cycle the plural times becomes smaller than a predetermined ratio, in a state where the integrated flow rate of the tungsten chloride gas per one cycle is kept substantially constant.