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:
Dec. 11, 1990
Filed:
Oct. 31, 1989
Hiroshi Kotaki, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
A method for fabricating a semiconductor memory device which includes a single substrate, at least one memory cell including at least one MOS transistor formed on the single substrate, and a peripheral circuit having at least one MOS transistor formed on the single substrate, comprises the steps of forming on the single substrate a gate electrode for each of the MOS transistors of the memory cell and the peripheral circuit, iono-implanting impurities at a low dosage by using the gate electrodes as a mask so as to forming a low impurity concentration of source/drain regions of the MOS transistors of the memory cell and the peripheral circuit, depositing a mask layer to cover an area of the memory cell, and ion-implanting impurities at a high dosage by using the mask layer as a mask, so as to dope impurities to only the source/drain regions of the MOS transistor of the peripheral circuit, so that the MOS transistor of the memory cell has the source/drain regions of a low impurity concentration, and the MOS transistor of the peripheral circuit has the source/drain regions including a high impurity concentration portion.