It is an object to provide a manufacturing method by which display devices can be manufactured in quantity without degrading the characteristics of thin film transistors. In a display device including a thin film transistor in which a microcrystalline semiconductor film, a gate insulating film in contact with the microcrystalline semiconductor film, and a gate electrode overlap with each other, an antioxidant film is formed on a surface of the microcrystalline semiconductor film. The antioxidant film on the surface of the microcrystalline semiconductor film can prevent a surface of a microcrystal grain from being oxidized, thereby preventing the mobility of the thin film transistor from decreasing.