A highly reliable semiconductor device that includes a transistor including an oxide semiconductor, which can display a high-definition image and can be manufactured with a high yield. The semiconductor device includes a pixel portion including a plurality of pixels, a gate signal line driver circuit portion, and a source signal line driver circuit portion including a first circuit that controls timing of sampling video signals and a second circuit that samples the video signals in accordance with the timing and then inputs the sampled video signals to the pixels. The second circuit includes a plurality of transistors in each of which an oxide semiconductor stacked layer is used as a channel formation region, the first circuit and the second circuit are electrically connected to each other by a wiring, and the wiring is electrically connected to gates of at least two transistors of the plurality of transistors.