Provided is a thin film transistor. The thin film transistor includes a substrate, a channel part extending on the substrate in a first direction parallel to an upper surface of the substrate, source/drain electrodes connected to both ends of the channel part in the first direction, and a gate electrode spaced apart from the channel part in a second direction intersecting the first direction and parallel to the upper surface of the substrate. Each of the channel part, the source/drain electrodes, and the gate electrode is provided as a single layer.