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:
Jul. 07, 1998
Filed:
Mar. 19, 1997
Hidekazu Takata, Nara, JP;
Hidehiko Tanaka, Nara, JP;
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
A non-volatile semiconductor memory device includes a plurality of memory cells each including a capacitor as a memory element, the capacitor sandwiching a ferroelectric member. The non-volatile semiconductor memory device further includes: a first counter for counting the number of write accesses and read accesses for writing or reading first logic data to each one of the plurality of memory cells; a second counter for counting the number of write accesses and read accesses for writing or reading second logic data to the memory cell; and a refresh control circuit for performing, when either a first value counted by the first counter or a second value counted by the second counter exceeds a predetermined value, a refresh operation by applying electric fields for causing a polarization state of the ferroelectric member of the capacitor to make a complete round on a hysteresis curve of the ferroelectric member in a corresponding one of the plurality of memory cells for which the first or second value counted by the first counter or the second counter has exceeded the predetermined value.