A display apparatus, such as an organic light emitting diode (“OLED”) display, is driven by thin film transistors (“TFTs”), including a driving TFT and a switching TFT, and a pixel electrode. The display apparatus includes an amorphous silicon layer for the switching TFT and a microcrystalline silicon or polycrystalline silicon layer for the driving TFT. The amorphous silicon layer and the microcrystalline silicon layer are separated by an insulating layer. The apparatus provides product reliability and high image quality. A method of manufacturing the apparatus is characterized by reducing processing steps, and using a special mask which is a half tone mask or a slit mask adapted to forming a source electrode and a drain electrode of the switching TFT or the driving TFT and a semiconductor layer during a photolithographic process.