There is provided a technique that includes: (a) forming a first film including a cyclic structure composed of silicon and carbon and also including nitrogen so as to fill a recess formed in a surface of a substrate by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing: supplying a precursor including the cyclic structure and also including halogen to the substrate having the recess formed on its surface; and supplying a nitriding agent to the substrate; (b) converting the first film into a second film including the cyclic structure and also including oxygen by supplying a first oxidizing agent to the substrate; and (c) converting the second film into a third film including silicon and oxygen and not including carbon and nitrogen by supplying a second oxidizing agent to the substrate.