Described herein is a technique capable of improving the uniformity of device characteristics. According to the technique described herein, there is provided a method of processing a substrate, including: (a) loading a substrate having a patterned hard mask into a process chamber; (b) supplying a metal-containing gas at a first pressure into the process chamber; and (c) supplying an inert gas into the process chamber and storing the metal-containing gas at a second pressure lower than the first pressure after performing (b).