A method of fabricating a thin film transistor of a thin film transistor liquid crystal display is provided. First, a patterned dielectric layer is formed over a substrate. A metallic layer is formed over the substrate to cover the patterned dielectric layer. Thereafter, the metallic layer is planarized until the patterned dielectric layer is exposed. The remained metallic layer serves as a gate. An insulating layer is formed over the patterned dielectric layer and the gate, and then a semiconductor layer is formed over the gate insulating layer above the gate. A source and a drain are formed over the semiconductor layer.