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:
Apr. 08, 1997
Filed:
Jun. 23, 1995
Nobuhiro Endo, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
In a floating-gate type nonvolatile memory cell, the second dielectric film between the floating gate and the control gate is made very higher in relative permittivity than the first dielectric film under the floating gate such that the relation .epsilon..sub.2 /.epsilon..sub.1 .gtoreq.13 and the relation t.sub.2 /t.sub.1 .gtoreq..epsilon..sub.2 /.epsilon..sub.1 hold, where .epsilon.and t represent relative permittivity and film thickness, respectively and subscripts 1 and 2 represent the first and second dielectric films, respectively. Strontium titanate, barium strontium titanate or lead zirconate-titanate is suitable as the material of the second dielectric film. In the case of, e.g. barium strontium titanate film, the proportion of Sr to Ba may vary in the direction of the film thickness. The second dielectric film may be made up of two (or more) different dielectric layers. The memory cell is low in writing and erasing voltages and excellent in endurance in terms of write/erase cycles.