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:
Sep. 14, 1999
Filed:
Oct. 31, 1997
Applicant:
Inventor:
Kiyoshi Nishimura, Kyoto, JP;
Assignee:
Rohm Co., Ltd., Kyoto, JP;
Primary Examiner:
Int. Cl.
CPC ...
G11C / ;
U.S. Cl.
CPC ...
365145 ; 365149 ;
Abstract
A semiconductor memory device with a plurality of memory cells each having a ferroelectric material for storing a data item by its residual polarization is made usable selectably both as a RAM and as a ROM by controlling the so-called 'imprint condition' of the ferroelectric material. When some of the memory cells are going to be used to a ROM or when the memory cells in an imprint condition are going to be used a RAM, heat and/or voltage pulses with an appropriate polarity are applied to the data-storing ferroelectric material to change its hysteresis characteristics.