Memory device and method of operating the memory device

A memory device comprising:

• a memory block connected to a plurality of lines;
• a peripheral circuit configured to perform a sensing operation on selected memory cells connected to a selected word line among the plurality of lines;
• a drain select line controller configured to control voltages applied to drain select lines among the plurality of lines, during the sensing operation and an equalizing operation performed after the sensing operation;
• a source select line controller configured to control voltages applied to source select lines among the plurality of lines;
• a word line controller configured to control a voltage applied to word lines between the drain select lines and the source select lines among the plurality of lines;
• and
• a dummy line controller configured to control a voltage applied to a center dummy line positioned in a middle of the word lines, when the memory block has a plurality of stack structures,
• wherein the drain select line controller controls a voltage applied to an unselected drain select line according to whether a cell string is shared with a selected drain select line among the drain select lines, during the sensing operation.

A method of operating a memory device including a memory block connected to a plurality of lines, the method comprising:

• applying a sensing voltage to a selected word line and applying pass voltages to unselected word lines among the plurality of lines in order to perform a sensing operation of sensing selected memory cells connected to the selected word line among the plurality of lines;
• and
• applying voltages to drain select lines among the plurality of lines, when applying the sensing voltage and the pass voltage,
• wherein a voltage applied to an unselected drain select line is set differently according to whether a cell string is shared with a selected drain select line among the drain select lines.