Shift register, semiconductor device, display device and electronic device

The present invention provides a semiconductor device and a shift register, which produces low noise and transistors are not always turned on in the non-selection period. A first to fourth transistors. A first line connected to the source and the drain of the first transistor, the other of the source and the drain is connected to the gate electrode of the second transistor, and a gate electrode connected to the fifth line. The source and the drain of the second transistor is connected to a third line, and the other of the source and the drain is connected to a sixth line. A source and a drain connected to the third transistor in the second line, the other of the source and the drain is connected to the gate electrode of the second transistor, and a gate electrode connected to the fourth line. The source and the drain of a fourth transistor is connected to the second line, a source electrode and a drain of the other is connected to the sixth line, and a gate electrode connected to the fourth line.