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:
Jan. 04, 1994
Filed:
Dec. 06, 1991
Applicant:
Inventors:
Isamu Kobayashi, Tokyo, JP;
Ryuuji Shibata, Higashiyamato, JP;
Assignee:
Hitachi, Ltd., Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H01L / ;
U.S. Cl.
CPC ...
437 29 ; 437 30 ; 437 44 ; 437 45 ; 437 52 ; 437 58 ;
Abstract
MISFET's are formed in the depletion mode in advance. MISFET's which are selected from these depletion-mode MISFET's are then formed into enhancement-mode or weak depletion-mode MISFET's to thereby write desired data into the memory cells of a read-only memory. The change of the MISFET's from the depletion mode into the enhancement mode (or weak depletion mode) is effected by introducing an impurity into the channel regions of the selected MISFET's in a manufacturing step that is carried out after the formation of the gate electrodes of the MISFET's.