Memory device and method of operating the same

A memory device comprising:

• a memory block including a plurality of select transistors;
• a peripheral circuit configured to perform a threshold voltage monitoring operation on the plurality of select transistors;
• and
• a control logic configured to control the peripheral circuit, and to reduce a select transistor operating voltage to be applied to the plurality of select transistors when a number of first select transistors in a lower threshold voltage distribution among the plurality of select transistors falls within a first setting range as a result of the threshold voltage monitoring operation, and increase the select transistor operation voltage when a number of second select transistors in an upper threshold voltage distribution among the plurality of select transistors falls within a second setting range.

A method of operating a memory device comprising:

• performing a first read operation using a first read voltage on a plurality of select transistors in a memory block;
• determining a number of first select transistors in a lower threshold voltage distribution area less than the first read voltage among the plurality of select transistors based on data read as a result of the first read operation;
• and
• reducing a potential level of a select transistor operating voltage to be applied to the plurality of select transistors when the number of first select transistors fails within a first setting range.