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:
May. 05, 1998
Filed:
Sep. 30, 1996
Yutaka Tomatsu, Okazaki, JP;
Mitsuhiro Kataoka, Kariya, JP;
Nippondenso Co., Ltd., Kariya, JP;
Abstract
A concave type DMOS transistor structure can attain improvement in a life-time of a gate insulating film. An initial groove portion is thermally oxidized with a silicon nitride film as a mask. A LOCOS oxide film is formed by this oxidation; concurrently, a U-groove is formed due to the erosion of the surface of an epitaxial layer by the LOCOS oxide film, and moreover the configuration of the groove is fixed. At this time, an inlet corner portion of the initial groove formed by chemical dry etching remains as a curving portion at a sidewall surface of the groove. Thereafter, a gate insulating film is formed, but thickness of the gate insulating film is controlled to be thicker on a groove inlet-portion side than on a groove bottom-portion side, with the curving portion as the boundary.