Semiconductor device

A semiconductor device comprising:

• a source wiring and a drain wiring each of which includes a first conductive layer and a second conductive layer having a smaller thickness than the first conductive layer;
• an insulating layer having an opening portion over the source wiring and the drain wiring;
• a semiconductor layer over the insulating layer;
• a gate insulating layer over the semiconductor layer;
• and
• a gate electrode over the gate insulating layer,
• wherein the semiconductor layer is in contact with a part of the source wiring or the drain wiring through the opening portion in a region comprising a single layer of the second conductive layer in the source wiring or the drain wiring, and
• wherein the semiconductor layer is an oxide semiconductor layer.

A semiconductor device comprising:

• a source wiring and a drain wiring each of which includes a first conductive layer and a second conductive layer having a smaller thickness than the first conductive layer;
• an insulating layer having an opening portion over the source wiring and the drain wiring;
• a semiconductor layer over the insulating layer;
• a gate insulating layer over the semiconductor layer;
• and
• a gate electrode over the gate insulating layer,
• wherein the semiconductor layer is in contact with a part of the source wiring or the drain wiring through the opening portion in a region comprising a single layer of the second conductive layer in the source wiring or the drain wiring,
• wherein the semiconductor layer is an oxide semiconductor layer, and
• wherein the insulating layer is provided so as to fill a space between the source wiring and the drain wiring.