Non-volatile memory device and operating method thereof

An operating method of a non-volatile memory device which comprises at least one cell string including a plurality of memory cells, a string select transistor and a ground select transistor arranged in a direction perpendicular to a substrate, the operating method comprising:

• erasing the plurality of memory cells;
• reading memory cells connected with a first word line using a first word line voltage;
• searching string address information corresponding to memory cells being at an off state;
• and
• storing mapping information indicating that memory cells corresponding to the string address information are programmed to a particular program state.

An operating method of a memory system, the memory system including a memory controller and a non-volatile memory, the non-volatile memory including a three-dimensional memory cell array comprising cell strings extending perpendicularly relative to a substrate and word lines intersecting the cell strings, the method comprising:

• identifying first string addresses corresponding to off-state cells among memory cells connected to a word line, and remaining second string addresses not corresponding to off-state cells among the memory cells connected to the word line;
• mapping original data corresponding to the first string addresses to first program states;
• and
• encoding the mapped data and data corresponding to the second string addresses.