Provided is a technique including forming a film by performing a cycle a predetermined number of times. The cycle includes: (a) forming a discontinuous first layer including the first element and having a thickness of less than one atomic layer on the substrate by supplying a gas containing the first element into a process vessel accommodating the substrate; and (b) forming a second layer including the first element and the second element by supplying a gas containing the second element into the process vessel to modify the first layer under a condition where a modifying reaction of the first layer by the gas containing the second element is not saturated.