US Patent 7649784 Memory cell programming methods capable of reducing coupling effects

In a memory cell programming method, first through n-th programming operations are performed to program first through n-th bits of the n bits of data using the plurality of threshold voltage distributions. The first through n-th programming operations are performed sequentially. A threshold voltage difference between threshold voltage distributions used in the n-th programming operation is less than or equal to at least one threshold voltage difference between threshold voltage distributions used in the first through (n−1)-th programming operations.