Patent ID: 7633089

Claim:
A liquid crystal display device comprising: a thin film transistor over a substrate, the thin film transistor comprising: a gate electrode over the substrate; a gate insulating film over the gate electrode and the substrate; a first island-shaped semiconductor layer and a second island-shaped semiconductor layer over the gate electrode with the gate insulating film interposed therebetween, each of the first and second island-shaped semiconductor layers including a microcrystalline semiconductor layer and a buffer layer on the microcrystalline semiconductor layer, each of the buffer layer of the first island-shaped semiconductor layer and the buffer layer of the second island-shaped semiconductor layer having a depression on an upper surface thereof; a first conductive semiconductor layer over the first island-shaped semiconductor layer; a second conductive semiconductor layer over the second island-shaped semiconductor layer; a third conductive semiconductor layer over the first and second island-shaped semiconductor layers and the gate insulating film; a first conductive layer over the first conductive semiconductor layer; a second conductive layer over the second conductive semiconductor layer; and a third conductive layer over the third conductive semiconductor layer, wherein the first, second, and third conductive semiconductor layers are not provided over the depressions of the first and second island-shaped semiconductor layers, wherein the first, second, and third conductive layers are not provided over the depressions of the first and second island-shaped semiconductor layers, and wherein the third conductive semiconductor layer is provided between the first and second island-shaped semiconductor layers to be directly in contact with the gate insulating film.