Abstract: The present invention relates to a method for manufacturing a semiconductor device including a method for reforming an insulating film formed by a low temperature CVD method. It is an object of the present Invention to provide a method for manufacturing a semiconductor device capable of improving a film quality of an insulating film formed by a CVD method which is able to form a film at a low temperature and also capable of maintaining mass productivity, in which processing by irradiation with ultraviolet rays of the insulating film while heating the film after forming an insulating film (4) on a body to be formed by a chemical vapor deposition method is included.