| CPC G06F 11/1004 (2013.01) | 17 Claims |

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1. A storage device comprising:
a memory device including a memory region including memory cells; and
a controller configured to set at least one prohibited threshold voltage distribution among a plurality of threshold voltage distributions formed by the memory cells when a predetermined condition is satisfied and configured to control a program operation of the memory device so that the memory cells do not form the prohibited threshold voltage distribution,
wherein the predetermined condition includes a number of fail bits in data read from the memory region exceeding a reference number.
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