Patent ID: 8330887

Claim:
A liquid crystal display device comprising: a substrate having an insulating surface; a transistor formed over the substrate; and a pixel electrode electrically connected to the transistor, wherein the transistor includes: a gate electrode; a gate insulating layer over the gate electrode; a semiconductor layer having a microcrystalline structure over the gate electrode with the gate insulating layer interposed therebetween; a buffer layer comprising an amorphous semiconductor, the buffer layer over the semiconductor layer having the microcrystalline structure; a source region over a first region of the buffer layer; and a drain region over a second region of the buffer layer, wherein the buffer layer comprises a groove between the first region and the second region, wherein the semiconductor layer includes a channel formation region, wherein a channel width W of the transistor and a channel length L of the transistor satisfy a relation of 0.1≦W/L≦1.7, and wherein a length of the gate electrode is larger than a length of the semiconductor layer in a direction of the channel length.