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. 18, 1998
Filed:
Aug. 21, 1995
Yugo Tomioka, Tokyo, JP;
Nippon Steel Corporation, Tokyo, JP;
Abstract
A nonvolatile semiconductor memory device including a plurality of memory cells, and a method of making this memory device. The nonvolatile semiconductor memory device includes: a semiconductor substrate; an element-isolation structure formed in a surface of the semiconductor substrate and having at least two linear portions extending in a longitudinal direction to define at least one element region between them; and at least one of the memory cells formed in the element region and including: a pair of impurity diffusion layers formed in the surface of said semiconductor substrate along each of the linear portions and a floating gate of a conductive material formed in the element region so as to extend in a lateral direction crossing the longitudinal direction and to bridge the two linear portions, the floating gate including at least a first portion formed on the surface of the semiconductor substrate through a tunnel oxide film and a second portion formed on the surface of the semiconductor substrate through a gate oxide film so as to cover the first portion, the tunnel oxide film having a thickness smaller than that of the gate oxide film, wherein the first portion overlaps through the tunnel oxide film with one of the impurity diffusion layers at an overlapping area extending in the longitudinal direction and having a width equal to or less than 0.18 .mu.m measured in the lateral direction.