METHOD OF READING DATA IN A NONVOLATILE MEMORY DEVICE

摘要

PURPOSE: A data reading method of a non-volatile memory device is provided to read accurate data with one read retry even when a read fails by determining an optimal read voltage level according to the number of on-cells (or off-cells) among monitoring cells. CONSTITUTION: A first read operation is performed to read data by applying a first read voltage having a first read voltage level to monitoring cells programmed to make data have programmed data cells and predetermined threshold voltages (S110). It is confirmed that a read fails in the first read operation (S130). A second read voltage level is determined according to the number of on-cells having threshold voltages in a voltage level lower than the first read voltage level among the monitoring cells when the read fails (S150). A second read operation is performed by applying a second read voltage having the second read voltage level to the data cells (S170). [Reference numerals] (AA) Start; (BB) No; (CC) Yes; (DD) Start; (S110) Perform a first read operation by applying a first read voltage having a first read voltage level to data cells and monitoring cells; (S130) Read fails?; (S150) Determine a second read voltage according to the number of on-cells among the monitoring cells; (S170) Perform a second read operation by applying a second read voltage having the second read voltage level to the data cells