It is an object to provide a semiconductor device which can supply a signal with sufficient amplitude to a scan line while power consumption is kept small. Further, it is an object to provide a semiconductor device which can suppress distortion of a signal supplied to the scan line and shorten a rising time and a falling time while power consumption is kept small. A semiconductor device which includes a plurality of pixels each including a display element and at least one first transistor and a scan line driver circuit supplying a signal for selecting the plurality of pixels to a scan line. A light-transmitting conductive layer is used for a pixel electrode layer of the display element, a gate electrode layer of the first transistor, source and drain electrode layers of the first transistor, and the scan line. The scan line driver circuit includes a second transistor and a capacitor for holding a voltage between a gate electrode layer of the second transistor and a source electrode layer of the second transistor. The source electrode of the second transistor is connected to the scan line.