A manufacturing method of a display device having TFTs capable of high-speed operation with few variations of threshold voltage is provided, in which materials are used with high efficiency and a small number of photomasks is required. The display device of the invention comprises a gate electrode layer and a pixel electrode layer formed over an insulating surface, a gate insulating layer formed over the gate electrode layer, a crystalline semiconductor layer formed over the gate insulating layer, a semiconductor layer having one conductivity type formed in contact with the crystalline semiconductor layer, a source electrode layer and a drain electrode layer formed in contact with the semiconductor layer having one conductivity type, an insulating later formed over the source electrode layer, the drain electrode layer, and the pixel electrode layer, a first opening formed in the insulating layer to reach the source electrode layer or the drain electrode layer, a second opening formed in the gate insulating layer and the insulating layer to reach the pixel electrode layer, and a wiring layer formed in the first opening and the second opening to electrically connect the source electrode layer or the drain electrode layer to the pixel electrode layer.