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

A method of manufacturing a semiconductor device, comprising:

• forming a thin film containing silicon, oxygen and carbon or a thin film containing silicon, oxygen, carbon and nitrogen on a substrate by performing a cycle two or more times, the cycle including:
• forming a first film containing silicon, oxygen and carbon or a first film containing silicon and oxygen by performing a set a predetermined number of times, the set including:
• supplying a precursor gas serving as a silicon source and a carbon source or a precursor gas serving as a silicon source but no carbon source, and a first catalyst gas to the substrate;
• and
• supplying an oxidizing gas and a second catalyst gas to the substrate;
• and
• causing reaction of the first film with a modifying gas under a non-plasma atmosphere to modify the first film into a second film further containing carbon, a second film further containing nitrogen, or a second film further containing carbon and nitrogen, the modifying gas containing at least one selected from the group consisting of carbon and nitrogen.