Writing method, reading method and memory device for hiding data

A memory device, comprising:

• a memory array comprising a memory block, wherein the memory block comprises a plurality of memory cells, the plurality of memory cells are respectively connected to a plurality of word lines and are constructed as a plurality of pages, wherein each of the plurality of memory cells comprises an erase state and a plurality of potential states, each of the plurality of potential states comprises a first sub-potential state and a second sub-potential state for hiding hidden data;
• and
• a memory controller coupled to the memory array,
• wherein the memory controller is configured to:
• for a specific potential state among the plurality of potential states, perform a first program operation on a plurality of memory cells of a first portion in a specific page to move threshold voltages of the plurality of memory cells of the first portion to the first sub-potential state of the specific potential state, wherein the plurality of pages comprise the specific page;
• and
• for the specific potential state, perform a second program operation on a plurality of memory cells of a second portion of the specific page to move threshold voltages of the plurality of the memory cells of the second portion to the second sub-potential state of the specific potential state,
• wherein the first program operation comprises:
• applying a first pass voltage to a first word line of a first page of the plurality of pages, wherein the first page is adjacent to a side of the specific page;
• and
• applying a second pass voltage to a second word line of a second page of the plurality of pages, wherein the second page is adjacent to another side of the specific page, wherein the first pass voltage is lower than the second pass voltage,
• wherein the second program operation comprises:
• applying a third pass voltage to the first word line of the first page, wherein the third pass voltage is higher than the first pass voltage;
• and
• applying a fourth pass voltage to the second word line of the second page, wherein the fourth pass voltage is lower than the third pass voltage.