The present invention discloses a thin film transistor (TFT), an array substrate comprising the TFT and a display device comprising the array substrate. The TFT comprises a gate, a source, a drain, and a semiconductor layer and an insulating layer which are both provided between the source, the drain and the gate, the insulating layer is made of inorganic insulating material, a modifying layer is provided between the insulating layer and the semiconductor layer and in an area corresponding to the insulating layer, and the modifying layer is made of organic aliphatic silane material. The surface of the insulating layer of the TFT is smoother with a state of less or substantially no surface defects.