A thin film transistor and a method of fabricating the same, an array substrate and a method of fabricating the same, and a display device are provided, the method of fabricating a thin film transistor includes: forming an active layer on a base substrate; forming a metal layer on the active layer; and processing the metal layer to form a source electrode, a drain electrode, and a metal oxide layer, the metal oxide layer covering the source electrode, the drain electrode, and the active layer, the source electrode and the drain electrode being spaced apart and insulated from each other by the metal oxide layer.