A thin film transistor (TFT) includes a substrate, a gate, a gate dielectric layer, a channel layer, a source and a drain. The gate and the gate dielectric layer are disposed on the substrate and the gate dielectric layer covers the gate. The channel layer is disposed on the gate dielectric layer over the gate, and the source and the drain are respectively disposed on a portion of the channel layer at both sides of the gate. At least one of the gate, the source and the drain has a lower conductive layer, an upper conductive layer and an intermediate conductive layer located between the lower conductive layer and the upper conductive layer. The material of the lower conductive layer is different from the material of the intermediate conductive layer, and the thickness of the lower conductive layer is less than or equal to about 150 Å.