1. A method of manufacturing a semiconductor device comprising: forming a semiconductor film over a substrate; crystallizing the semiconductor film by using a material for promoting crystallization; introducing a chemical element selected from group 15 of the periodic table into a region of the crystallized semiconductor film becoming at least an electrode of auxiliary capacitor; forming an insulating film over the crystallized semiconductor film; and forming a metal layer over at least the region with the insulating film interposed therebetween.