Provided are a thin film transistor and manufacturing method thereof, array substrate and manufacturing method thereof, and display device. The thin film transistor comprises: an active layer, an etch stop layer disposed on the active layer, an overcoating layer disposed on the etch stop layer, and a source electrode and a drain electrode disposed on the overcoating layer, wherein the overcoating layer comprises at least one of a conductive material layer, a non-transparent insulation layer and a non-transparent semiconductor layer, and the source electrode and the drain electrode are electrically connected with the active layer.