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);
a circuit including data holding circuits connected to the bit lines, the data holding circuits holding data to be written to the memory cells,
the circuit configured to:
simultaneously select i number of memory cells among h number of memory cells (h is equal to or more than i) connected to a first word line of the word lines; and
write, before writing first data of next at least single value to the i number of memory cells storing second data of m values (m is less than n), third data having a value equal to or less than the m values to k number of memory cells among j number of memory cells (j is equal to or more than k) connected to a second word line adjacent to the first word line.
2. The semiconductor memory device according to claim 1 , wherein
when the first data of the at least single value is written to the i number of memory cells storing the second data of the m values and connected to the first word line,
the circuit changes a logical levels of g number of memory cells (g is equal to or less than h) connected to the first word line from a first level to a second level.
3. The semiconductor memory device according to claim 2 , wherein
fourth data is simultaneously read from the h number of memory cells, and
the fourth data of the h number of memory cells is determined based on fifth data of the g number of memory cells.
4. The semiconductor memory device according to claim 1 , wherein the memory cells are nonvolatile memory cells.
5. The semiconductor memory device according to claim 1 , wherein each of the word lines extends in a first direction, and each of the bit lines extends in a second direction crossing the first direction.
6. The semiconductor memory device according to claim 1 , wherein each of the memory cells includes a floating gate and a control gate, physically separated from each other.
7. The semiconductor memory device according to claim 1 , wherein the memory cell array is a memory cell array of a NAND flash memory.
8. The semiconductor memory device according to claim 1 , wherein the circuit is configured to control potentials of the word lines and potentials of bit lines.
9. The semiconductor memory device according to claim 1 , wherein the data holding circuits hold data read from the memory cells.