A thin film transistor fabrication method allows forming a first photoresist pattern on a triple layer of insulation, conductive and metal films opposite to a semiconductor pattern. A first metal pattern and a conductive pattern are formed through an etch process before forming source and drain regions through a first ion injection process. A second photoresist pattern with a narrower width than that of the first photoresist pattern is derived from the first photoresist pattern. The first metal pattern is reformed into a second metal pattern with a narrower width than that of the second photoresist pattern. A process is performed that includes removing the second photoresist pattern, forming LDD (Lightly Doped Drain) regions in the semiconductor pattern, and forming GOLDD (Gate Overlap LDD) regions in the semiconductor pattern. A second insulation film is formed before forming source and drain electrodes on the second insulation film.