Patent ID: 8471252

Claim:
A semiconductor device including a thin film transistor, the thin film transistor comprising: a first metal oxide layer having n-type conductivity over a source electrode layer; a second metal oxide layer having n-type conductivity over a drain electrode layer; an oxide semiconductor layer over the first metal oxide layer and the second metal oxide layer; a gate insulating layer over the oxide semiconductor layer; and a gate electrode layer over the gate insulating layer, wherein the source electrode layer and the drain electrode layer are formed over a substrate, wherein a carrier concentration of the first metal oxide layer and the second metal oxide layer is higher than a carrier concentration of the oxide semiconductor layer, wherein the oxide semiconductor layer and the source electrode layer are electrically connected to each other with the first metal oxide layer interposed therebetween, and wherein the oxide semiconductor layer and the drain electrode layer are electrically connected to each other with the second metal oxide layer interposed therebetween.