Provided is a semiconductor device exemplified by an inverter circuit and a shift register circuit, which is characterized by a reduced number of transistors. The semiconductor device includes a first transistor, a second transistor, and a capacitor. One of a source and a drain of the first transistor is electrically connected to a first wiring, and the other thereof is electrically connected to a second wiring. One of a source and a drain of the second transistor is electrically connected to the first wiring, a gate of the second transistor is electrically connected to a gate of the first transistor, and the other of the source and the drain of the second transistor is electrically connected to one electrode of the capacitor, while the other electrode of the capacitor is electrically connected to a third wiring. The first and second transistors have the same conductivity type.