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. 20, 2002
Filed:
Aug. 30, 2000
Junichi Yamada, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
There is provided a highly reliable non-volatile ferroelectric memory device in which the permitted number of read/write operation cycles is increased. The device comprises a step-down power supply circuit which generates a supply voltage VINT which is lower than a supply voltage VDD fed from the outside but not less than a coercive voltage of the ferroelectrics for the purpose of improving the resistance to fatigue of and imprinting to the ferroelectrics. Since the characteristics of the ferroelectrics deteriorate more due to fatigue and imprinting as the voltage applied to the ferroelectrics increases, a supply voltage for sense amplifiers and voltage supply circuits are selected to be VINT so that VINT is applied to the ferroelectric capacitors, while a supply voltage for other peripheral circuits is selected to be VDD. With this structure, the reliability of the device with respect to its read/write operations can significantly be improved as compared to the conventional ferroelectric memory devices by minimizing the effect that the signal voltage is reduced and by increasing the permitted number of operation cycles.