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:
Nov. 23, 2004
Filed:
Jan. 13, 2004
Noriyuki Matsui, Kawasaki, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
A multi-value memory that has an improved data maintain period has been disclosed and, in a multi-value nonvolatile semiconductor memory device comprising a multi-value memory cell having a floating-gate and able to store at least three values, the threshold values of the multi-value memory cell are set from a state in which the threshold values designate at least two boundary values that identify at least three values to a state in which a fixed quantity of charges are injected into the floating gate in a data write operation, the read data is determined from the relationship between the threshold values of the multi-value memory cell and the (at least) two boundary values, and increments (margins) A , A and A in the threshold value from threshold values VT , VT and VT , which are the lower limits of ranges, due to the injection of charges into the floating gate in the data write operation are set so that the increment is larger for data corresponding to a state in which a larger quantity of charges are injected.