To provide a method of forming a wiring for the purpose of providing a semiconductor device, which is superior in reliability and cost performance. Further, to provide methods of manufacturing a semiconductor device and a display device by using the method of forming the wiring according to the present invention. According to the present invention, when a wiring material and the like is directly patterned on a substrate mainly having an insulating surface by droplet discharging method, a wiring is formed at a position including at least an opening in contact with an underlying portion on an insulating film provided with the opening by dropping a liquid droplet containing a conductive composition by droplet discharging method. By heating the substrate with the wiring formed thereon, a surface of the wiring on the opening and a surface of the wiring other than the wiring on the opening are approximately leveled, and the opening is filled.