There is provided a method of manufacturing a semiconductor device, which includes: forming a first seed layer containing silicon and germanium on a substrate by performing, a predetermined number of times, a cycle which includes supplying a first process gas containing silicon or germanium and containing a halogen element to the substrate, supplying a second process gas containing silicon and not containing a halogen element to the substrate, and supplying a third process gas containing germanium and not containing a halogen element to the substrate; and forming a germanium-containing film on the first seed layer by supplying a fourth process gas containing germanium and not containing a halogen element to the substrate.