Patent ID: 8563976

Claim:
A semiconductor device comprising: a first gate electrode over a substrate having a light-transmitting property, the first gate electrode having a light-transmitting property; a first insulating layer over the first gate electrode, the first insulating layer comprising a first layer and a second layer over the first layer; a first oxide semiconductor layer over and in contact with the second layer; a barrier layer over the first oxide semiconductor layer, the barrier layer having a light-transmitting property; a first electrode over the first oxide semiconductor layer with the barrier layer interposed therebetween, the first electrode overlapping with the first gate electrode; a second electrode over the first oxide semiconductor layer with the barrier layer interposed therebetween, the second electrode overlapping with the first gate electrode; a second insulating layer over the first electrode and the second electrode and in contact with a part of the first oxide semiconductor layer; and a third insulating layer over and in contact with the second insulating layer, wherein the barrier layer includes a nitride, wherein a carrier concentration of the first oxide semiconductor layer is lower than 1×10 14 cm 3 , wherein the first electrode and the second electrode each includes an oxide conductor having a light-transmitting property and a resistivity of 2000×10 −6 Ω·cm or lower, and wherein the third insulating layer is in contact with a side surface of the second layer and a top surface of the first layer.