[Purpose] It is an object to obtain a crystalline silicon film having preferable characteristics for a thin film transistor. [Structure] A crystalline silicon film having improved crystallinity is obtained by the following steps: forming a silicon nitride film substantially in contact with an amorphous silicon film on glass substrate; introducing a catalyst element such as nickel; performing an annealing treatment at a temperature of 500 to 600° C. for crystallization; and further irradiating it with a laser light, thereby a crystalline silicon film having improved crystallinity can be obtained. By using the crystalline silicon film thus obtained, a semiconductor device such as a TFT having improved characteristic can be obtained.