Memory device and method of performing program operation

A memory device comprising:

• a memory cell array including memory cells connected to M word lines;
• a peripheral circuit configured to apply operation voltages to the M word lines during a voltage increase period in which a voltage level of an Nth word line, selected among the M word lines, increases to a target level;
• and
• a control logic configured to control the peripheral circuit to:
• apply a step-up voltage to (N±1)th word lines, adjacent to the Nth word line, for a first period of time after a program voltage is applied to the Nth word line, and
• apply a step-down voltage, the step-down voltage being different from the step-up voltage, to the (N±1)th word lines for a second period of time after the first period of time,
• wherein the peripheral circuit is configured to apply the step-up voltage and the step-down voltage to the (N±1)th word lines in the voltage increase period.

A method of operating a memory device, the method comprising:

• applying a program voltage to a select word line, selected among a plurality of word lines connected to memory cells;
• applying a step-up voltage to adjacent word lines, adjacent to the select word line, for a first period of time after the program voltage is applied;
• and
• applying a step-down voltage, the step-down voltage being less than the step-up voltage, to the adjacent word lines for a second period of time after the first period of time,
• wherein the step-up voltage and the step-down voltage are applied to the adjacent word lines in a voltage increase period in which a voltage level of the select word line increases to a target level.