Method of manufacturing semiconductor device, substrate processing method, substrate processing apparatus, and recording medium

A method of manufacturing a semiconductor device, comprising:

• etching a first film exposed on a surface of a substrate by performing a cycle two or more times, the cycle including non-simultaneously performing:
• (a) forming a first modified layer in at least a portion of a surface of the first film by supplying a first gas to the substrate;
• and
• (b) etching at least a portion of the first film with an etching species and forming a second modified layer, which is removable by the first gas, in at least a portion of the surface of the first film having at least the portion etched, by supplying a second gas having a molecular structure different from that of the first gas to the substrate, wherein the etching species is generated by performing at least one selected from the group of causing the second gas to react with the first modified layer and activating the first modified layer with the second gas.