Thin film transistor and method of making the same

A method for fabricating a thin film transistor, the method comprising the steps of:

• sequentially forming a buffer layer and an amorphous-silicon layer;
• converting the amorphous-silicon layer to a poly-silicon layer by a low temperature crystallization process;
• forming a gate insulating layer having a silicon nitride and a silicon oxide on the poly-silicon layer, a channel region is defined on the gate insulating layer, and the channel region of the gate insulating layer is etched to expose the poly-silicon layer needed for an ohmic contact;
• simultaneously depositing an ohmic contact layer and a metal gate layer on the gate insulating layer and the poly-silicon layer, and etching an extra region of the ohmic contact layer and the metal gate layer to reserve the ohmic contact layer;
• forming a gate electrode on the gate insulating layer;
• forming a dielectric layer on the gate electrode and the gate insulating layer, as well as forming through holes;
• and
• forming a source electrode and a drain electrode on the through holes.