Aspects of the invention provide a method, in a semiconductor device, such as a thin film transistor, a technology capable of preventing or reducing the electric field concentration at the edge section of the semiconductor film to enhance the reliability. The method of manufacturing a semiconductor device according to the invention can include a first step of forming a semiconductor film discretely on an insulation substrate, a second step of covering the semiconductor film including an edge section of the semiconductor film with a first insulation film, a third step of opening the first insulation film above the semiconductor film excluding the edge section of the semiconductor film, a fourth step of forming a second insulation film thinner than the first insulation film on the semiconductor film corresponding to at least the opening of the first insulation film, and a fifth step of forming an electrode wiring film on the second insulation film.