It is an object to provide a liquid crystal display device and an electronic device of which aperture ratio increases. The present invention includes a substrate having an insulating surface, a transistor formed over the substrate, a pixel electrode electrically connected to the transistor. The transistor includes a gate electrode, a gate insulating layer over the gate electrode, a semiconductor layer having a microcrystalline structure over the gate insulating layer, and a buffer layer over the semiconductor layer having the microcrystalline structure. The channel width W of the transistor and the channel length L of the transistor satisfy a relation of 0.1≦W/L≦1.7.