A thin film transistor, a method for manufacturing the same, an array substrate and a display device are disclosed. The thin film transistor includes a gate having a gate metal layer on a surface of a substrate; a gate insulating layer on the substrate and covering the gate; an active layer on a surface of the gate insulating layer away from the substrate; a source comprising a source metal layer on a surface of the active layer away from the substrate; and a drain having a drain metal layer on a surface of the active layer away from the substrate, wherein the gate, the source or the drain further includes a metal complex layer on a surface of the gate metal layer, the source metal layer or the drain metal layer away from the substrate.