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

There is provided a technique that includes: forming a film containing Si, O and N or a film containing Si and O on a substrate by performing a cycle a predetermined number of times under a condition where SiCl4 is not gas-phase decomposed, the cycle including non-simultaneously performing: (a) forming NH termination on a surface of the substrate by supplying a first reactant containing N and H to the substrate; (b) forming a SiN layer having SiCl termination formed on its surface by supplying the SiCl4 as a precursor to the substrate to react the NH termination formed on the surface of the substrate with the SiCl4; and (c) reacting the SiN layer having the SiCl termination with a second reactant containing O by supplying the second reactant to the substrate.