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:
Apr. 09, 2013
Filed:
Oct. 31, 2007
Yoshinori Yoshida, Fussa, JP;
Tatsuya Tominari, Tachikawa, JP;
Toshio Ando, Kunitachi, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
The external base electrode has a two-layered structure where a p-type polysilicon film doped with a medium concentration of boron is laminated on a p-type polysilicon film doped with a high concentration of boron. Therefore, since the p-type polysilicon film doped with a high concentration of boron is in contact with an intrinsic base layer at a junction portion between the external base electrode and the intrinsic base layer, the resistance of the junction portion can be reduced. In addition, since the resistance of the external base electrode becomes a parallel resistance of the two layers of the p-type polysilicon films, the resistance of the p-type polysilicon film whose boron concentration is relatively lower is dominant.