PURPOSE: To improve both the mobility of field effect and the characteristics by a method wherein a part of a polycrystalline silicon thin film is brought into an amorphous state by ion-implanting silicon into the above-mentioned part, crystal grains are grown from the region where ions are not implanted to the ion-implanted region, and a thin film transistor is formed by having the growing direction cf crystal grain as the channel length direction.

CONSTITUTION: A polycrystalline silicon thin film 301 is formed on an amorphous substrate 300, a part of the polycrystalline silicon thin film is brought into an amorphous state by ion-implanting silicon there. Then, in a crystallizing process in which a heat treatment is added, crystal grains are grown from the above-mentioned region where silicon is hot ion-implanted to the region where silicon is ion-implanted. Then, a thin film transistor is formed using said crystal growing direction as a channel length direction. For example, after the thin film 301 which is crystallized as above has been divided into each transistor region 303 by conducting a photolithographic process, a silicon oxide film 304, which is a gate oxide film, and a gate electrode 305 are formed. Subsequently, a source region 306 and a drain region 307 are formed by ion-implanting phosphorus, and they are activated by conducting a heat treatment.