A thin film transistor, which has a first passivation layer and a second passivation layer to maintain high reliability while preventing hydrogen from being induced to a semiconductor layer, and a method for fabricating the thin film transistor are provided. The method includes providing a substrate including an insulation substrate, forming a gate electrode on the substrate, forming a gate insulation layer on the substrate and the gate electrode, forming a semiconductor layer on the gate insulation layer, forming source/drain electrodes on the semiconductor layer to expose a portion of a top portion of the semiconductor layer, forming a first passivation layer to cover exposed top portions of the gate insulation layer, the semiconductor layer and the source/drain electrodes, and forming a second passivation layer on the first passivation layer, wherein the forming of the second passivation layer comprises performing deposition at a higher temperature than the forming of the first passivation layer.