Abstract: A method of manufacturing a thin film transistor capable of inhibiting the characteristics variation of the thin film transistor without deteriorating the characteristics thereof is provided. A crystalline silicon film is formed by indirect heat treatment through a photothermal conversion layer and a buffer layer. By patterning the buffer layer and an insulating film, a channel protective film is selectively formed in a region corresponding to a channel region on the crystalline silicon film. Further, when an n+ silicon film and a metal layer are selectively removed, the channel protective film functions as an etching stopper. When the crystalline silicon film is formed, heat is uniformly supplied. Further, in etching, the channel region of the crystalline silicon film is protected.