The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 16, 2000
Filed:
Oct. 03, 1997
Toshio Takeshima, Tokyo, JP;
Hiroshi Sugawara, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
In order to reduce the number of erase operations of a nonvolatile memory cell which stores a threshold voltage selected from among a plurality of threshold levels, a plurality of programming operations are implemented before an erase operation. That is, the programming operations are executed which respectively vary the threshold voltage of the memory cell to a different one of the plurality of threshold levels, or retain the previously stored threshold voltage of the memory cell. Thereafter, the memory cell is erased so as to return the voltage which is stored in the memory cell to a predetermined level, in response to all of the threshold levels having been used in the programming operations.