Thin film transistor and method for manufacturing the same, array substrate and display device

A method for manufacturing a thin film transistor, comprising:

• forming a gate electrode on a substrate, and forming a gate insulating layer on the gate electrode;
• forming a semiconductor layer, and forming a metal oxide insulator layer on the semiconductor layer;
• and
• forming source/drain electrodes;
• wherein the metal oxide insulator layer covers a channel region between the source/drain electrodes;
• wherein forming of the metal oxide insulator layer comprises:
• performing exposing, developing and etching onto a metal oxide insulator thin film for forming the metal oxide insulator layer to form an insulator layer that has overlapping regions with the source/drain electrodes to be formed;
• and
• performing a via hole process on the insulator layer to form via holes that electrically connect the source/drain electrodes with the semiconductor layer in the overlapping regions in the metal oxide insulator layer;
• the semiconductor layer and the insulator layer have a same size along a direction parallel to the substrate.