A method of manufacturing a thin film transistor is disclosed. The method includes forming an amorphous silicon layer and a blocking layer on an insulating substrate, forming a photoresist layer having first and second photoresist patterns on the blocking layer, etching the blocking layer using the first photoresist pattern as a mask to form first and second blocking patterns, reflowing the photoresist layer, forming a metal layer over the entire surface of the insulating substrate, removing the photoresist layer to expose the blocking layer and an offset region between the blocking layer and the metal layer, crystallizing the amorphous silicon layer to form a poly silicon layer having a MILC front, etching the polysilicon layer using the first and second blocking patterns as a mask to form first and second semiconductor layers and to remove the MILC front, and removing the first and second blocking patterns.