NON-VOLATILE SEMICONDUCTOR MEMORY AND ITS OPERATION METHOD

摘要

PROBLEM TO BE SOLVED: To improve a lifetime of a non-volatile semiconductor memory by performing weak writing, making only a memory cell having large movement in read-disturbe '0' cell, and discovering easily a memory cell having large movement. SOLUTION: A redundant circuit consisting of a second memory cell array 21 and a second row decoder 22 is used for replacing a memory cell with a redundant memory cell when a cell having large movement exists in read- disturb. Week page writing is performed with a shorter pulse than a writing pulse at the time of writing data so that a threshold value of a normal cell is smaller than read-out voltage at the time of reading data. At the time, As a writing speed of a cell having large movement in read-disturb is faster than that of a normal cell, it is made a '0' cell. Next, a cell having large movement can be easily discriminated by verifying whether a '0' cell exists or not.