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:
Oct. 30, 1990
Filed:
Apr. 13, 1988
Toshiyuki Shimizu, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
For increasing a retaining time period of a data bit, there is disclosed a semiconductor memory cell comprising a switching transistor and a storage capacitor fabricated in a semiconductor substrate formed with a heavily doped layer and a lightly doped layer, a transition layer graded in impurity atom concentration is produced between the heavily doped layer and the lightly doped layer, and the storage capacitor comprises (a) a first electrode formed by a first side wall portion of the lightly doped layer, a second side wall portion of the heavily doped layer and a bottom wall portion of the heavily doped layer, (b) a dielectric film formed in the first and second side wall portions and the bottom wall portion and defining a trench and (c) a second electrode formed on the trench and contacting the dielectric film, wherein the dielectric film has a relatively thin portion and a relatively thick portion which covers the transition layer so as to reduce in strength of electric field around the transition layer.