The invention includes a two terminal switching device having two stable resistivity values for each applied voltage, which when a voltage of not more than a first threshold voltage (Vth1) is applied, becomes in a first state having a higher resistivity, whereas when a larger second threshold voltage (Vth2) or more is applied, becomes in a second state having a lower resistivity; a resistance connected in series to the switching device; a terminal for applying a bias voltage (Vt) to both ends of a series circuit of the switching device and the resistance; a first pulse inputting terminal; and a second pulse inputting terminal. The invention provides a simple realization of a flip-flop circuit for a sequential logic circuit.