Disclosed is a method of driving a transistor including a semiconductor layer, a first insulating layer, a second insulating layer, a first conductive layer, and a second conductive layer such that the semiconductor layer is disposed between the first and second insulating layers, one surface of the first insulating layer opposite the other surface in contact with the semiconductor layer is in contact with the first conductive layer, one surface of the second insulating layer opposite the other surface in contact with the semiconductor layer is in contact with the second conductive layer. The method includes applying a voltage VBG that satisfies the relation of VBG≦VON1×C1/(C1+C2) to the second conductive layer.