A thin film transistor that has improved characteristics and uniformity is developed by uniformly controlling low concentration of crystallization catalyst and controlling crystallization position so that no seed exists and no grain boundary exists, or one grain boundary exists in a channel layer of the thin film transistor. The thin film transistor includes a substrate; a semiconductor layer pattern which is formed on the substrate, the semiconductor layer pattern having a channel layer of which no seed exists and no gram boundary exists; a gate insulating film formed on the semiconductor layer pattern; and a gate electrode formed on the gate insulating film. A method for fabricating the thin film transistor includes forming an amorphous silicon layer on a substrate; forming a semiconductor layer pattern having a channel layer in which no seed exists and no grain boundary exists by crystallizing and patterning the amorphous silicon layer; forming a gate insulating film on the semiconductor layer pattern; and forming a gate electrode on the gate insulating film.