There is provided a method of manufacturing a semiconductor device, comprising forming a film on a substrate by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing forming a first layer by supplying a precursor containing hydrogen and an halogen element to the substrate in a process chamber, under a condition in which the precursor is pyrolyzed if the precursor exists alone and under a condition in which a flow rate of the precursor supplied into the process chamber is larger than a flow rate of the precursor exhausted from an interior of the process chamber and forming a second layer by supplying a reactant to the substrate in the process chamber thereby modifying the first layer.