Memory device and method of operating the memory device

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

• applying a first read voltage among a plurality of read voltages to a selected word line;
• applying a first pass voltage to unselected word lines;
• applying a second read voltage different from the first read voltage among the plurality of read voltages to the selected word line;
• and
• applying a second pass voltage higher than the first pass voltage to the unselected word lines,
• wherein one of the first and second read voltages is a read voltage for determining a program state of memory cells having a threshold voltage higher than a reference voltage among the plurality of read voltages, and the other is a read voltage for determining a program state of memory cells having a threshold voltage lower than the reference voltage among the plurality of read voltages, and
• wherein the reference voltage is a read voltage having an intermediate magnitude among the plurality of read voltages.

A storage device comprising:

• a memory device configured to perform a read operation on memory cells;
• and
• a memory controller configured to control the memory device according to a request of a host,
• wherein the memory device, during the read operation, is configured to:
• selectively apply a first read voltage for determining a program state of memory cells having a threshold voltage higher than a reference voltage and a second read voltage for determining a program state of memory cells having a threshold voltage lower than the reference voltage to a selected word line coupled to selected memory cells among the memory cells,
• apply a first pass voltage to unselected word lines coupled to unselected memory cells among the memory cells when the first read voltage is applied to the selected word line, and
• apply a second pass voltage higher than the first pass voltage to the unselected word lines when the second read voltage is applied to the selected word line.