Memory device and method of operating the same

A method of operating a memory device, comprising:

• performing a sub-program operation of applying a program voltage to a plurality of memory cells included in a selected page;
• performing a verify operation to verify threshold voltages of selected memory cells having a lowest target voltage, selected from among the plurality of memory cells;
• and
• comparing a number of passed bits detected in the verify operation with a reference number of passed bits,
• skipping a current sensing check operation of determining whether the verify operation has passed or failed in a next program loop when the number of passed bits is less than the reference number of passed bits;
• and
• performing the current sensing check operation from the next program loop when the number of passed bits is equal to or greater than the reference number of passed bits.

A method of operating a memory device, comprising:

• performing a plurality of program loops for increasing threshold voltages of memory cells in a selected page,
• wherein, in each of the plurality of program loops,
• when a number of memory cells whose threshold voltages have increased up to a target voltage, is less than a reference number of memory cells, a current sensing check operation of determining a result of a verify operation of a previous program loop is skipped, and
• when the number of memory cells whose threshold voltages have increased up to the target voltage, is equal to or greater than the reference number of memory cells, the current sensing check operation is performed.