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:
Feb. 18, 2014
Filed:
Aug. 23, 2011
Takashi Nakano, Osaka, JP;
Yukio Tamai, Osaka, JP;
Nobuyoshi Awaya, Osaka, JP;
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
The invention provides a semiconductor memory device including a variable resistance element capable of decreasing a variation of a resistance value of stored data due to a large number of times of switching operations and capable of performing a stable writing operation. The device has a circuit that applies a reforming voltage pulse to a memory cell including a variable resistance element of a degraded switching characteristic and a small read margin due to a large number of times of application of a write voltage pulse, to return each resistance state of the variable resistance element to an initial resistance state. By applying the reforming voltage pulse, the variable resistance element can recover at least one resistance state from a variation from the initial resistance state, and can recover the switching characteristic. Accordingly, there is obtained a semiconductor memory device in which a reduction of a read margin is suppressed.