A semiconductor display device comprising a pixel portion and a signal line driver circuit comprising a first circuit, a second circuit configured to control timing of the sampled serial video signals by the first circuit, and a third circuit configured to perform signal processing on the parallel video signals, wherein the second circuit comprises a first semiconductor element formed over a first substrate, the first semiconductor element including a first semiconductor layer, wherein the third circuit comprises a second semiconductor element formed over a second substrate, the second semiconductor element including a second semiconductor layer, wherein the pixel portion comprises a third semiconductor element formed over the second substrate, the third semiconductor element including a third semiconductor layer, wherein the first semiconductor layer comprises silicon or germanium, and wherein each the second semiconductor layer and the third semiconductor layer has a wider bandgap than the first semiconductor layer.