An organic light emitting diode display includes: a substrate including a first and a second gate electrode formed over a first and a second region, respectively, a first and a second gate insulator formed on the first and the second gate electrode, respectively, a first and a second semiconductor layer formed on the first and the second gate insulator, respectively, the first semiconductor layer including a first channel region, the second semiconductor layer including a second channel region, an interlayer insulator formed over the substrate and over at least part of the first and second semiconductor layers, a first and a second etching stop layer formed over the first and second channel regions, respectively, and surrounded by the interlayer insulator, and a first and a second source electrode and a first and a second drain electrode contacting the first and the second semiconductor layer, respectively, through the interlayer insulator.