An insulating film is formed on a target substrate by CVD, in a process field to be selectively supplied with a first process gas containing a silane family gas, a second process gas containing a nitriding gas, and a third process gas containing a carbon hydride gas. This method includes repeatedly performing supply of the first process gas to the process field, supply of the second process gas to the process field, and supply of the third process gas to the process field. The supply of the third process gas includes an excitation period of supplying the third process gas to the process field while exciting the third process gas by an exciting mechanism.