A thin film transistor is provided. The transistor includes a gate; a first passivation layer covering the gate; a channel layer disposed on the first passivation layer; a source and a drain that are disposed on the first passivation layer and contact two sides of the channel layer; a second passivation layer covering the channel layer, the source, and the drain; first and second transparent electrode layers that are disposed on the second passivation layer and spaced apart from each other; a first transparent conductive via that penetrates the second passivation layer and connects the source and the first transparent electrode layer; and a second transparent conductive via that penetrates the second passivation layer and connects the drain and the second transparent electrode layer. A cross-sectional area of the gate is larger than a cross-sectional area of the channel layer, the source, and the drain combined.