NONVOLATILE MEMORY SYSTEM BEING CAPABLE OF REDUCING READ DISTURBANCE

摘要

A non-volatile memory device is provided to change a level of an unselected read voltage according to an SLC(Single Level Cell) block and an MLC(Multi-Level Cell) block, thereby reducing performance deterioration of a memory cell caused by read disturbance. A memory cell array(110) is connected to plural word lines. The memory cell array has an MLC block(112) and an SLC block(111). A voltage generating circuit(140) provides a selection read voltage for a selective word line. The voltage generating circuit provides an unselected read voltage to an unselected word line. The unselected read voltage is changed according to the number of data bits stored in a memory cell. The unselected read voltage is higher than the selection read voltage. A read voltage selector selects a level of the unselected read voltage.