Embodiments of the present invention provide a thin film transistor, an array substrate and a display device. The thin film transistor comprises a gate layer, a first insulating layer, an active layer, an etch stop layer and a source/drain electrode layer, wherein the active layer is made of a metal oxide material, the first insulating layer, the active layer, the etch stop layer and the source/drain electrode layer are sequentially stacked from bottom to top, the source/drain electrode layer contains an interval separating a source electrode and a drain electrode therein, the etch stop layer is located below the interval, and the etch stop layer has a width greater than that of the interval, and the first insulating layer comprises a laminate of a first sub-insulation layer and a second sub-insulation layer, the second sub-insulation layer is in contact with the active layer and made of an oxygen-rich insulating material.