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:
Jun. 28, 2005
Filed:
Mar. 11, 2003
Shigekazu Yamada, Kawasaki, JP;
Shigekazu Yamada, Kawasaki, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
A nonvolatile semiconductor memory device includes a memory cell array which includes memory cells and reference cells, the reference cells including a first reference cell and a second reference cell. A data discriminating control unit generates an average reference level based on a reference level supplied from the first reference cell and a reference level supplied from the second reference cell, and the data discriminating control unit determining whether data is zero or one by comparison of a read-out level of each of the memory cells with the average reference level. A reference cell setting unit performs program verification for each memory cell with respect to a threshold level of the first reference cell to obtain a distribution of threshold levels of the memory cells, and the reference cell setting unit setting a threshold level of the second reference cell based on the distribution of the threshold levels of the memory cells.