Memory device and operating method thereof

A memory device comprising:

• a plurality of memory blocks each including a plurality of memory cell strings each including a plurality of memory cells connected in series between a common source line and a bit line, a plurality of source select lines connected in series between the common source line and the plurality of memory cells, and a plurality of drain select lines connected in series between the bit line and the plurality of memory cells;
• a peripheral circuit configured to perform a plurality of program loops each including a program voltage apply step of providing a program voltage to a selected memory block among the plurality of memory blocks and a verify step of verifying a program state of the selected memory block;
• and
• a program operation controller configured to control the peripheral circuit to precharge channel regions of the plurality of memory cell strings through the common source line and to set a bit line voltage applied to the bit line, at a predetermined time with respect to starting precharging the channel regions of the plurality of memory cell strings, in the program voltage apply step.

A method for operating a memory device including a plurality of memory cell strings each including a plurality of memory cells connected between a common source line and a bit line, a source select line connected between the common source line and the plurality of memory cells, and a drain select line connected between the bit line and the plurality of memory cells, the method comprising:

• increasing a voltage of the common source line;
• increasing a voltage applied to the source select line of each of the plurality of memory cell strings through the common source line;
• and
• setting, after a predetermined elapsed time, a bit line voltage applied to the bit line, after the voltage applied to the source select line of each of the plurality of memory cell strings is increased, while the voltage applied to the source select line of each of the plurality of memory cell strings is increased.