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:
Oct. 20, 2015
Filed:
Sep. 03, 2013
Kabushiki Kaisha Toshiba, Tokyo, JP;
Masaki Fujiu, Kanagawa, JP;
Kabushiki Kaisha Toshiba, Tokyo, JP;
Abstract
A semiconductor memory device includes a plurality of memory strings each of which includes a series of memory cells that each store data having n bits (n≧3), word lines, each connected in common to memory cells of different memory strings, and a control circuit which controls a first write operation and a second write operation. The first write operation includes a first step where a middle threshold voltage distribution is formed in memory cells and a second step following the first step where threshold voltages of some of the memory cells are increased, and the second write operation includes a step where threshold voltage distributions which correspond to the data having n bits is formed in the memory cells, wherein a write verify operation is performed after the first step but not after the second step of the first write operation.