A manufacturing method of a thin film transistor (TFT) includes forming a gate electrode including a metal that can be combined with silicon to form silicide on a substrate and forming a gate insulation layer by supplying a gas which includes silicon to the gate electrode at a temperature below about 280° C. The method further includes forming a semiconductor on the gate insulation layer, forming a data line and a drain electrode on the semiconductor and forming a pixel electrode connected to the drain electrode.