The disclosure relates to a thin film transistor. The thin film transistor may include a substrate, an active layer on the substrate, a gate on the active layer, and a source and a drain. The active layer may include a first conducting region, a second conducting region, and a channel region between the first conducting region and the second conducting region. An orthographic projection of the source and an orthographic projection of the drain on the substrate may cover at least an orthographic projection of a first conducting region and an orthographic projection of a second conducting region on the substrate.