It is an object to form a conductive region in an insulating film without forming contact holes in the insulating film. A method is provided, in which an insulating film is formed over a first electrode over a substrate, a first region having many defects is formed at a first depth in the insulating film by adding first ions into the insulating film at a first accelerating voltage; a second region having many defects is formed at a second depth which is different from the first depth in the insulating film by adding second ions into the insulating film at a second accelerating voltage, a conductive material containing a metal element is formed over the first and second regions; and a conductive region which electrically connects the first electrode and the conductive material is formed in the insulating film by diffusing the metal element into the first and second regions.