Embodiments of the present invention provide a TFT array substrate and a method for manufacturing the same and a display device. The TFT array substrate comprises: a base substrate; gate lines, gate electrodes, a gate insulating layer and a semiconductor active layer formed on the base substrate; a metal barrier layer formed on the semiconductor active layer, the metal barrier layer covering the semiconductor active layer; source electrodes and drain electrodes formed on the metal barrier layer, with a metal oxide part being formed between the source electrode and the drain electrode to insulate the source electrode and the drain electrode from each other; and a protection layer formed on the gate insulating layer and the source and drain electrodes, wherein the metal oxide part is formed by oxidizing a part of the metal barrier layer located between the source electrode and the drain electrode.