A thin film including characteristics of low permittivity, high etching resistance and high leak resistance is to be formed. A method of manufacturing a semiconductor device includes forming a thin film containing a predetermined element on a substrate by performing a cycle a predetermined number of times, the cycle including: forming a first layer containing the predetermined element, nitrogen and carbon by alternately performing supplying a source gas containing the predetermined element and a halogen element to the substrate and supplying a first reactive gas containing three elements including the carbon, the nitrogen and hydrogen and having a composition wherein a number of carbon atoms is greater than that of nitrogen atoms to the substrate a predetermined number of times; and forming a second layer by supplying a second reactive gas different from the source gas and the first reactive gas to the substrate to modify the first layer.