A thin film transistor, a method for manufacturing the same, an array substrate and a display device are provided. The method for manufacturing a thin film transistor includes: providing a substrate; forming an active layer and a light shielding layer covering the active layer on the substrate by a patterning process, the light shielding layer being formed of a photoresist material; and forming a source-drain electrode layer and a passivation layer covering the source-drain electrode layer.