There is provided a technique that includes forming a first film including a ring-shaped structure composed of silicon and carbon and containing nitrogen so as to fill a recess formed in a surface of a substrate by performing a cycle a predetermined number of times, and performing post-treatment by supplying an oxidizing agent to the substrate under a condition that the ring-shaped structure included in the first film is preserved. The cycle includes non-simultaneously performing supplying a precursor including the ring-shaped structure and containing halogen to the substrate with the recess formed in the surface, and supplying a nitriding agent to the substrate, wherein the cycle is performed under a condition that the ring-shaped structure included in the precursor is preserved.