Nonvolatile semiconductor memory device having electrically and collectively erasable characteristics

Abstract

A semiconductor memory device has 2n word lines, a plurality of bit lines, a plurality of nonvolatile memory cells disposed at each intersection of the word lines and the bit lines, a write circuit for writing data to a memory cell located at an intersection of selected ones of the word lines and the bit lines, and a sense amplifier for reading data out of the memory cells. Further, the semiconductor memory device comprises a first unit for simultaneously selecting a block of 2m (n>m) word lines among the 2n word lines, and a second unit for not selecting a block of 2k (m>k) word lines among the 2m word lines. The second unit does not select the block of 2k word lines, and selects a block of 2k word lines prepared outside the 2n word lines when any one of the 2k word lines among the 2m word lines is defective. Consequently, redundant word lines are effectively employed, write and verify operations are stable, and thereby the yield and performance of the semiconductor memory device are improved.

Dependencies are inferred from the claim text.