Array substrate and display device and method for making the array substrate

A method for making an array substrate comprising:

• forming a poly-silicon semiconductor layer on a substrate;
• forming a buffer layer on the substrate and covering the poly-silicon semiconductor layer;
• depositing a first metal layer and patterning the first metal layer to form a first gate electrode for a driving TFT, a second gate electrode for a switch TFT, and a third gate electrode for a poly-silicon TFT, the third gate electrode overlapping with the poly-silicon semiconductor layer;
• forming a first gate insulator layer covering the third gate electrode and the first gate electrode;
• forming a second gate insulator layer covering the first gate insulator layer and the second gate electrode;
• defining a first through hole and a second through hole in the second gate insulator layer, the first through hole and the second through hole passing through the buffer layer, the first gate insulator layer, and the second gate insulator layer to expose the poly-silicon semiconductor layer;
• depositing a metal oxide layer on the second gate insulator layer and patterning the metal oxide layer to form a first metal oxide semiconductor layer and a second metal oxide semiconductor layer, the first metal oxide semiconductor layer overlapping with the first gate electrode and the second metal oxide semiconductor layer overlapping with the second gate electrode;
• and
• depositing a second metal layer and patterning the second metal layer to form a first source electrode, a first drain electrode, a second source electrode, a second drain electrode, a third source electrode, and a third drain electrode, the first source electrode and the first drain electrode coupled to the first metal oxide semiconductor layer of the driving TFT, the second source electrode and the second drain electrode coupled to the second metal oxide semiconductor layer of the switch TFT, and the third source electrode in the first through hole and the third drain electrode in the second through hole.