Patent ID: 8318551

Claim:
A semiconductor device comprising: a gate electrode layer, a first source electrode layer, and a first drain electrode layer each formed using the same material layer over a substrate; a gate insulating layer over the gate electrode layer; an oxide semiconductor layer over the gate insulating layer, the first source electrode layer, and the first drain electrode layer; and a second source electrode layer and a second drain electrode layer over the oxide semiconductor layer, the first source electrode layer, and the first drain electrode layer, wherein a first part of a bottom surface of the oxide semiconductor layer is in contact with the first source electrode layer, a second part of the bottom surface is in contact with the first drain electrode layer, and a third part of the bottom surface is in contact with the gate insulating layer, wherein a first part of a top surface of the oxide semiconductor layer is in contact with the second source electrode layer, and a second part of the top surface is in contact with the second drain electrode layer, and wherein the first source electrode layer is electrically connected to the second source electrode layer, and the first drain electrode layer is electrically connected to the second drain electrode layer.