Nonvolatile semiconductor memory device which stores multi-value information
US5870218A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 30, 1997 |
| Grant date | Feb 9, 1999 |
| Priority date | — |
| Expiry date | Apr 30, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C2211/5642
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
To enable one non-volatile memory cell to store four-value information, three different kinds of threshold voltages are serially applied to a word line in a verify operation to execute a write operation, the threshold voltages of the memory cell are controlled, and two-value (one-bit) information corresponding to the four-value (two-bit) information to be written are synthesized by a write data conversion circuit for each of the write operations carried out three times. In this way, the four-value (two-bit) information are written into one memory cell, and the memory capacity of the memory cell can be increased. In the information read operation, three different kinds of voltages are applied to a word line, three kinds of two-value (one-bit) information so read out are synthesized by a read conversion circuit and the memory information of the memory cell are converted to the two-bit information.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.