Semiconductor memory device for storing multivalued data
Data storage circuits are connected to the bit lines in a one-to-one correspondence. A write circuit writes the data on a first page into a plurality of 5 first memory cells selected simultaneously by a word line. Thereafter, the write circuit writes the data on a second page into the plurality of first memory cell. Then, the write circuit writes the data on the first and second pages into second memory cells adjoining 10 the first memory cells in the bit line direction.
1. A semiconductor memory device comprising:
a memory cell array in which memory cells are provided in a matrix, the memory cells connected to word lines and bit lines, the memory cells storing one of n values (n is a natural number equal to or larger than 3); and
data holding circuits connected to the bit lines and holding data to be written to the memory cells,
wherein, after a writing of the data is performed to the memory cells and a verification for writing of data of (k−1) value (k≤n) is performed according to the data of the data holding circuits,
a verification for writing of data of k value is performed using a first verify level corresponding to a value less than the k value and a second verify level corresponding to the k value,
when a threshold voltage of the memory cell does not reach the first verify level, the data of the data holding circuit is not changed,
when the threshold voltage of the memory cell reaches the first verify level and does not reach the second verify level, the data of the data holding circuit is set as the data of the (k−1) value, and
when the threshold voltage of the memory cell reaches the second verify level, the data of the data holding circuit is set as non-write data,
a writing of the data is performed to the memory cells according to the data of the data holding circuits after the verification of the k value.
2. The semiconductor memory device according to claim 1 , further comprising:
a first cell holding information for the writing of the data of the k value,
wherein the information is not set to the first cell in the writing of the data of the (k−1) value, and the information is set to the first cell in the writing of the data of the k value.
3. The semiconductor memory device according to claim 2 , wherein a reading for the memory cells is performed based on the information.
4. The semiconductor memory device according to claim 2 , wherein
the data of the memory cell is determined based on the information.
5. The semiconductor memory device according to claim 1 , wherein
the writing and the verification is repeatedly performed.