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:
Sep. 17, 2002
Filed:
Dec. 26, 2000
Seiichi Mori, Tokyo, JP;
Hiroyuki Sasaki, Yokkaichi, JP;
Hideo Kato, Kawasaki, JP;
Hidetoshi Saito, Yokohama, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
This invention discloses a memory cell threshold voltage shift method effective for the erase or write sequence of a nonvolatile semiconductor memory. First, the threshold voltages V of a plurality of memory cells are shifted at once to a range whose upper limit is set to an erase verify voltage V . After this, the lower limit of the threshold voltages V shifted at once to the range is shifted to a first overerase verify voltage V close to the erase verify voltage V . Then, the lower limit of the threshold voltages V shifted to the first overerase verify voltage V to a second overerase verify voltage V closer to the erase verify voltage V .