Abstract: An address buffer circuit for a semiconductor memory device includes first and second address inputs which are selectably connectable to a first node according to first and second address input control signals, respectively. The device also includes first and second switches which are controlled by a refresh mode signal and selectively output a first or second address enable signal. Further, a latch is provided which latches the address signal input to the first node, and outputs the latched address signal in periods of the selected first or second address enable signals.

Abstract: In a highly integrated semiconductor memory device, apparatus for setting a stress mode without applying a stress voltage from the exterior is provided. A triggered time point T.sub.S to a stress mode can be set by greatly raising an internal supply voltage when the external supply voltage is raised to a voltage over the stress voltage.

Abstract: A back-bias level sensor used for a semiconductor device wherein a sensing current for sensing a back-bias voltage is prevented from directly flowing into the substrate (or the back-bias voltage terminal). The gate of a PMOS transistor is provided with the back-bias voltage while the source is provided with a ground voltage, so that a pump circuit performs the pumping operation to increase the back-bias voltage when the back-bias voltage is lower than a predetermined voltage level; otherwise, the pump circuit is de-energized, thereby reducing the back-bias voltage.