High performance semiconductor memory device that has different page addresses allotted to multiple bits of memory cells

1. A semiconductor memory device, comprising:

a memory cell array including a plurality of memory cells, each memory cell configured to store plural bits of data; and

a controller configured to execute a write operation on the memory cells such that user data are written in at least one of the plural bits of data of said each memory cell and prescribed data are written in the remaining bits of the plural bits of data of said each memory cell,

wherein the number of bits of user data stored in said each memory cell is less than the number of plural bits of data that said each memory cell is configured to store.

2. The semiconductor memory device of claim 1 , wherein the controller is configured to execute the write operation on the memory cells such that the user data are written in two or more plural bits of data of said each memory cell.

3. The semiconductor memory device of claim 1 , wherein the prescribed data are 1's.

4. The semiconductor memory device of claim 1 , wherein the prescribed data are 0's.

5. The semiconductor memory device of claim 1 , wherein the prescribed data have values that match a value of a highest order bit of the user data.

6. The semiconductor memory device of claim 1 , wherein the plural bits of data are stored in said each memory cell as a distribution of threshold voltages.

7. The semiconductor memory device of claim 6 , wherein the controller is configured to shift one or more of the threshold voltages.

8. The semiconductor memory device of claim 1 , wherein the write operation is an en bloc write operation.

9. A semiconductor memory device configured for a write operation, comprising:

a memory cell array including a plurality of pages, each page including a plurality of memory cells, each memory cell being configured to store three or more bits of data; and

a controller configured to execute the write operation on the pages such that x bits of data are written in a first memory cell included in a first page selected from the plurality of pages and y bits of data are written in a second memory cell included in a second page selected from the plurality of pages, where x is different from y.

10. The semiconductor memory device of claim 9 , wherein the bits of data are stored in the memory cells as a distribution of threshold voltages.

11. The semiconductor memory device of claim 10 , wherein the controller is configured to shift one or more of the threshold voltages.

12. A method of controlling a semiconductor memory device comprising a memory cell array including a plurality of memory cells, each memory cell configured to store N bits of data (where N is an integer greater than 1), said method comprising:

executing a write operation on the memory cells such that user data are written in i bits of data (where i is an integer less than N) and prescribed data are written in the remaining bits of the N bits of data; and

storing a parameter i in a nonvolatile state.

13. The method of claim 12 , further comprising:

upon power-on, reading a parameter i; and

executing a read operation on the memory cells to read i bits of data from each of the memory cells.

14. The method of claim 12 , wherein the prescribed data are all 1's or all 0's.

15. The method of claim 12 , wherein the prescribed data have values that match a value of a highest order bit of the user data.

16. The method of claim 12 , further comprising:

shifting one or more of threshold voltages that are set in the memory cells as a result of executing the write operation.

17. The method of claim 12 , wherein the write operation is an en bloc write operation.