A film formation apparatus for a semiconductor process includes a source gas supply circuit to supply into a process container a source gas for depositing a thin film on target substrates, and a mixture gas supply circuit to supply into the process container a mixture gas containing a doping gas for doping the thin film with an impurity and a dilution gas for diluting the doping gas. The mixture gas supply circuit includes a gas mixture tank disposed outside the process container to mix the doping gas with the dilution gas to form the mixture gas, a mixture gas supply line to supply the mixture gas from the gas mixture tank into the process container, a doping gas supply circuit to supply the doping gas into the gas mixture tank, and a dilution gas supply circuit to supply the dilution gas into the gas mixture tank.