SEMICONDUCTOR MEMORY DEVICE AND CORRECTION METHOD OF REFERENCE CELL, IN WHICH DEGRADATION OF REFERENCE CELL DUE TO DISTURBANCE IS PREVENTED

摘要

PURPOSE: A semiconductor memory device and a correction method of a reference cell are provided, which check the state of the reference cell efficiently and correct the reference cell and prevent the degradation of the reference cell due to disturbance and thus maintain a level of the reference cell accurately. CONSTITUTION: A chip is divided into a plurality of sectors(S1-Sj). According to the semiconductor memory device per each sector, a plurality of memory cells(1) stores and program N level data. A memory access circuit(7) performs a read operation and a program operation and an erase operation as to each memory cell. A reference cell(2) stores a reference level used to read a data level stored in each memory cell. A counter circuit(3) counts the number of reading of the reference cell. A check unit(4) judges whether the reference level stored in the reference cell is within a set range. And a correction unit(5) corrects the reference level on the ground of a master reference cell(6) if the judged reference level is not within the set level.