An object is to provide a level shift circuit that operates stably. A semiconductor device includes a level shift circuit including first to fourth transistors and a buffer circuit. One of a source and a drain (S/D) of the first transistor is connected to one of a source and a drain of the second transistor. The other of the source and the drain of the second transistor is connected to one of a source and a drain of the third transistor. A gate of the first transistor and a gate of the fourth transistor are connected to the other of the source and the drain of the second transistor and the one of the source and the drain of the third transistor. A gate of the third transistor is connected to a wiring to which an input signal is input. An input terminal of the buffer circuit is connected to one of a source and a drain of the fourth transistor. An output terminal of the buffer circuit is connected to a gate of the second transistor and a wiring to which an output signal is output.