Negative voltage generator and semiconductor memory device

Abstract

A negative voltage generator includes a variable-capacitance negative voltage generating unit, a switching unit and a positive voltage applying unit. The negative voltage generating unit includes a plurality of coupling capacitors for varying the capacitance in which the negative voltage is charged. The negative voltage generating unit selects at least one coupling capacitor of the plurality of coupling capacitors according to the number of rows (size) of a memory bank to which data is written, and charges the at least one selected coupling capacitor to a negative voltage. The switching unit selects one bitline of a bitline pair having complementary first and second bitlines in response to the data, and connects the at least one selected coupling capacitor to the selected bitline. The positive voltage applying unit applies a positive (high) voltage to an other bitline of the bitline pair.