A method of manufacturing a semiconductor device, includes forming a first insulating film containing silicon oxide as a main ingredient, on an underlying region, adhering water to the first insulating film, forming a polymer solution layer containing a silicon-containing polymer on the water-adhered first insulating film, and forming a second insulating film containing silicon oxide as a main ingredient from the polymer solution layer, wherein forming the second insulating film includes forming silicon oxide by a reaction between the polymer and water adhered to the first insulating film.