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:
Dec. 31, 2002
Filed:
Feb. 15, 2000
Kiyoteru Kobayashi, Tokyo, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
A semiconductor device and its manufacturing method which not only can solve the problem that a memory cell size determines a write/erase speed of memory cell transistors but also can increase the write/erase speed while preventing the reduction in the reliability of an insulating film between a control gate and a second-layer floating gate. Since the insulating film under a second-layer floating gate has irregularity, the second-layer floating gate itself has irregularity, whereby its surface area and hence the write/erase speed is increased. Further, since the insulating film under the second-layer floating gate has irregularity, protrusions on the surface of the second-layer floating gate are rounded. Therefore, the degree of electric field concentration is reduced, whereby the reliability of the insulating film between the control gate and the second-layer floating gate is prevented from being lowered.