A thin film transistor, method of manufacturing the thin film transistor, an array substrate comprising the thin film transistor, and a display device comprising the array substrate. The thin film transistor comprises a substrate; a first electrode on the substrate; an active layer on a side of the first electrode away from the substrate; and a second electrode on a side of the active layer away from the first electrode. The first electrode and the second electrode are connected to the active layer, respectively. are also disclosed.