SEMICONDUCTOR MEMORY DEVICE, IN WHICH VIRTUAL GROUND LINE IS USED AND READ OPERATION MARGIN IS NOT DEGRADED

摘要

PURPOSE: A semiconductor memory device is provided to achieve large capacity and high speed operation, by preventing the degradation of read operation margin due to a current injected to a selected bit line from an unselected bit line. CONSTITUTION: According to a memory array(1), a memory cell has one first electrode and a pair of second electrodes, and memory content is read by the conduction of the second electrode according to a potential of the first electrode. The memory cell array has a plurality of memory cells constituted in a matrix along a row direction and a column direction. A device isolation zone is installed along the column direction at every 4 cells in the row direction. The memory cell array is divided into a plurality of sub arrays(2) by the device isolation zone.