Column redundancy circuit for a semiconductor memory device

Abstract

A column redundancy circuit for a semiconductor memory device, e.g., a DRAM, which includes a normal memory array comprised of a plurality of memory blocks each comprised of a matrix of rows and columns of memory cells, with at least two of the memory blocks sharing common columns, and with at least one of the columns being defective, in the sense of being connected to at least one memory cell which has been determined to be defective. The column redundancy circuit includes a plurality of redundant columns, block selection control circuit which is programmed to generate a first output signal in response to receipt of a memory block address signal corresponding to one or more of the memory blocks which contain the defective column, a column address decoder which is programmed to generate a second output signal in response to receipt of both the first output signal and a column address signal corresponding to the defective column, and, a redundant column driver circuit which is responsive to the second output signal for activating a predetermined one of the redundant columns, to thereby repair the defective column. In a preferred embodiment, the block selection control circuit and the column address decoder each include a plurality of fuses and are each programmed by means of a selected one or more of their fuses being blown, e.g., by use of a laser.