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:
Aug. 27, 2002
Filed:
Oct. 10, 2000
Toshihiro Tanaka, Akiruno, JP;
Masataka Kato, Kaganei, JP;
Osamu Tsuchiya, Hamura, JP;
Toshiaki Nishimoto, Tachikawa, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A nonvolatile semiconductor memory device is provided which includes a plurality of memory cells each having a floating gate, wherein a threshold level of each memory cell depends on a value of electric charge in said floating gate of said memory cell, and wherein said threshold level of each memory cell is placed at one of a first area and a second area. A controller is also provided which controls to set each threshold voltage of selected ones of said plurality of memory cells, wherein said controller performs a first setting operation and a verifying operation. The first setting operation shifts threshold voltages of the selected ones of said plurality of memory cells in a direction from said first area to said second area. The verifying operation detects erratic memory cells which have threshold voltages which are on a side of said second area which is opposite of a middle area formed between the first area and the second area.