Semiconductor memory devices

Abstract

A semiconductor memory device having at least one memory cell array block with a plurality of memory cells formed at the surface of a semiconductor substrate. Each memory cell includes a transistor and memory capacitor. The device further has a plurality of word lines for addressing the memory cells, a plurality of bit lines for reading from and writing to the memory capacitors, at least one cell plate formed on the semiconductor substrate, the cell plate forming a common electrode of the memory capacitors, a cell plate voltage generator for supplying a voltage of a level between the supply voltage and the ground voltage to the cell plate, and a control circuit for controlling the output impedance of the cell plate voltage generating unit.