US Patent 7843723 Semiconductor memory device capable of reading data reliably

A control unit reads data from a plurality of memory cells connected to one of the word lines in a read operation at a first level CR generated by a voltage generator circuit and in a read operation at a second level CR−x and finds the number of cells included between the first level and the second level from the data and, if the number is equal to or smaller than a specified value, determines the result of the read operation at the first level to be read data.