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. 31, 2004
Filed:
Apr. 11, 2003
Hiroyuki Doi, Toyama, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
A constant voltage device includes n-type and p-type doped layers. The n-type doped layer is formed by heavily doping with an n-type impurity an upper portion of a p-type silicon semiconductor substrate, in an active region defined by an isolating insulator film. The p-type doped layer is formed by doping the region under the n-type doped layer with a p-type impurity. The n-type and p-type doped layers are provided to form two layers in parallel with the substrate surface of the semiconductor substrate, whereby a pn junction formed between the n-type and p-type doped layers creates a diode structure. Impurity concentration in the p-type doped layer is established so that the impurity concentration of a portion adjacent the isolating insulator film is lower that that of the rest.