Patent ID: 8878574

Claim:
A method for driving a semiconductor device comprising a first wiring, a second wiring, a first transistor, a second transistor whose conductivity type is different from a conductivity type of the first transistor, and a third transistor having a channel formation region including a semiconductor, a band gap of which is higher than a band gap of silicon and an intrinsic carrier density of which is lower than an intrinsic carrier density of silicon, wherein one of a source and a drain of the first transistor is electrically connected to the first wiring, and the other of the source and the drain of the first transistor is electrically connected to one of a source and a drain of the second transistor, and wherein one of a source and a drain of the third transistor is electrically connected to the other of the source and the drain of the second transistor, and the other of the source and the drain of the third transistor is electrically connected to the second wiring, the method comprising: in a first period, turning off the third transistor when the first transistor is switched from one of an on state and an off state to the other of the on state and the off state, and turning on the third transistor when one of the first transistor and the second transistor is turned on and the other of the first transistor and the second transistor is turned off; and in a second period after the first period, turning off the third transistor regardless of a state of the second transistor.