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:
Sep. 19, 1989
Filed:
Aug. 17, 1988
Takeshi Kasahara, Saitama, JP;
Toko, Inc., , JP;
Abstract
A method of making a variable-capacitance diode device including semiconductor layer a first conductivity type in which the impurity concentration decreases with increasing depth from surface of a PN junction. The semiconductor layer of the first conductivity type is formed by diffusing an impurity element of the first conductivity type in a semiconductor substrate with a high degree of concentration. Thereafter, a semiconductor layer of a second conductivity type is formed which has such an impurity concentration profile that the concentration of impurity element of the second conductivity type is lower than the impurity concentration of said semiconductor layer of the first conductivity type formed in said semiconductor substrate and at a predetermined depth, the concentration of the second conductivity type impurity element is substantially equal or close to the concentration of the first conductivity type impurity element. Subsequent to the formation of the first conductivity type semiconductor layer, an impurity element of the second conductivity type is diffused so as to define said PN junction with said first conductivity type semiconductor layer.