Thin film transistor substrate and organic light-emitting diode display including the same

A thin film transistor (TFT) substrate, comprising:

• a substrate;
• and
• a TFT located on the substrate and comprising:
• a lower gate electrode;
• a first insulating layer covering the lower gate electrode;
• an oxide semiconductor layer located on the first insulating layer;
• a first electrode located on the oxide semiconductor layer and having an island shape;
• a second electrode located on the oxide semiconductor layer and surrounding the first electrode;
• a second insulating layer at least partially covering the oxide semiconductor layer;
• and
• an upper gate electrode located on the second insulating layer,
• wherein the oxide semiconductor layer includes a first region, a second region surrounding the first region, and a third region interposed between the first and second regions,
• wherein the first electrode is located in the first region of the oxide semiconductor layer,
• wherein the second electrode is located in the second region of the oxide semiconductor layer,
• wherein the lower and upper gate electrodes face each other, and wherein the third region of the oxide semiconductor layer is interposed between the lower and upper gate electrodes.