A method of manufacturing a semiconductor device and a substrate processing apparatus capable of providing a TiN film at a higher film-forming rate. The method includes loading a substrate into a processing chamber; simultaneously starting a supply of a first processing gas and a second processing gas to form a film on the substrate, simultaneously stopping the supply of the first and second processing gas; removing the remaining first and second processing gas from the processing chamber; supplying the second processing gas into the processing chamber without supplying the first processing gas; removing the second processing gas starting and then stopping a supply of the first processing gas into the processing chamber without supplying the second processing gas; removing the first processing gas; and unloading the substrate from the processing chamber.