Memory device permitting overwrite program operation and operation method thereof

Abstract

A memory device comprising: a memory cell array including memory cells coupled between a word line and a plurality of bit lines, and a control unit suitable for performing a program operation of repeating a program loop including a voltage application operation and a verification operation on the memory cells according to an Incremental Step Pulse Program (ISPP) method until the program operation is performed successfully, wherein the control unit repeatedly performs the program loop by setting a voltage level of an initial program pulse to one of first and second levels according to whether the program operation is an overwrite operation or not, wherein the initial program pulse is to be applied to the word line in the voltage application operation included in an initial program loop of the repeated program loops, and wherein the second level is lower than the first level by a first set level.