Semiconductor device

A semiconductor device comprising:

• a pixel portion;
• and
• a circuit in a peripheral part of the pixel portion, comprising:
• a first transistor, a second transistor, a third transistor and a fourth transistor;
• and
• a first wiring, a second wiring, a third wiring, a fourth wiring, a fifth wiring and a sixth wiring,
• wherein the first wiring is electrically connected to one of a source and a drain of the first transistor and one of a source and a drain of the second transistor,
• wherein the second wiring is electrically connected to one of a source and a drain of the third transistor and one of a source and a drain of the fourth transistor,
• wherein the third wiring is electrically connected to a gate of the first transistor and a gate of the third transistor,
• wherein the fourth wiring is electrically connected to a gate of the second transistor and a gate of the fourth transistor,
• wherein the fifth wiring is electrically connected to the other of the source and the drain of the first transistor,
• wherein the sixth wiring is electrically connected to the other of the source and the drain of the third transistor,
• wherein each of the first transistor, the second transistor, the third transistor and the fourth transistor comprises an oxide semiconductor layer,
• wherein a first video signal is supplied to the first wiring,
• wherein a second video signal is supplied to the second wiring, and
• wherein the oxide semiconductor layer comprises a first oxide semiconductor film and a second oxide semiconductor film which are stacked with each other.