A laser annealing method for obtaining a crystalline semiconductor film having a large grain size, and a method of manufacturing a semiconductor device using the crystalline semiconductor film, are provided. Using a shape change (convex portion or concave portion) of an amorphous semiconductor film when crystallizing the amorphous semiconductor film using irradiation of laser light, it is possible to intentionally regulate the origin of crystal growth, and to make the grain size large. By then designing the arrangement of an active layer (island shape semiconductor film) so as to contain at least a channel forming region within one grain, it becomes possible to improve the electrical characteristics of a TFT.