Fujitsu Corporation

Fujistu Limited

Katsuya Yoshida

Tamiji Akita

Kenji Ijitsu

A plurality of dummy bit lines are disposed together with a plurality of bit line pairs in a memory cell array. In selectively driving a memory cell connected to the bit line pair, a timing control circuit controls the timing of the driving operation, based on signal change in the plural dummy bit lines, thereby detecting the influences of the process variation in a plurality of positions in the memory cell array. Thus, the influence of the process variation given to the operation of a semiconductor memory device can be further alleviated, compared with the case when one dummy bit line is used.

Semiconductor memory device

A redundancy decision circuit for specifying a redundant memory cell in a memory cell array when a normal cell is defective. The circuit includes a switching element, a fuse and a load circuit connected in series between high and low potential supplies. A switching driver drives the switching element. A hold circuit latches the potential at a node between the switching element and one of either the fuse and the load circuit. The circuit then generates a redundant decision signal.

Redundant decision circuit for semiconductor memory device

The present invention concerns a memory structure wherein a plurality of memory cells such as SRAM are provided in columns and a plurality of bit line pairs are provided for each column. A write circuit drives a first bit line pair and writes data to the memory cells in the column; at the same time, a sense amp reads data by means of the second bit line pair. In that case, the first bit line pair and second bit line pair, provided in the same column, are driven with opposite phase signals. To prevent the reversal of the small potential difference of the second bit line pair for reading at that time, two bit lines, one bit line from the first and second bit line pairs, are arranged parallel in a first wiring layer and are interspersed with a fixed potential wiring. Furthermore, the two other bit lines from the first and second bit line pairs, are arranged parallel in a second wiring layer provided via an insulating layer and are interspersed with a fixed potential wiring. With such a structure, the first bit line pair and second bit line pair are disposed in each wiring layer and interposed in the fixed potential wiring; therefore, crosstalk therebetween is prevented even when the bit line pairs are driven with opposite phase signals and erroneous read operations are prevented.

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Kawasaki, Japan

Katsuya Yoshida