Semiconductor memory with multiple sets & redundant cells

Abstract

An area of a semiconductor chip, on which a memory is disposed, is divided into a plurality of memory blocks and redundant memory blocks, each memory block is divided into a plurality of unit arrays of columns for replacing, each redundant memory block is divided into a plurality of unit arrays of redundant columns, a plurality of memory cells are disposed in each unit array of columns for replacing and each unit array of redundant columns, a memory cell group in each unit array of columns for replacing is connected to a word line and a data line, a redundant memory cell group of each unit array of redundant columns is connected to a redundant word line and a redundant data line, a first data selection circuit for controlling data selection with respect to the unit array of redundant columns is disposed in each memory block, a second data selection circuit for controlling data selecting with respect to the unit array group of redundant columns is disposed in each redundant memory block, and a third data selection circuit for selecting and transmitting only data selected either of the data selection circuit is disposed, wherein, if each memory block has no defect, data selected by the first data selection circuit, that is, data selected from the unit array of columns for replacing of each memory block is transmitted as it is by way of the third data selection circuit, if any one of the memory blocks has a defect, data selection with respect to the unit array of columns for replacing that has encountered the defect is inhibited, the unit array of redundant columns of the redundant memory block is instructed in place of the unit array of columns for replacing that has encountered the defect, and data is, by the second data selection circuit, selected from the selected unit array of redundant columns in place of the replacement unit array that has encountered the defect as to transmit the selected data by way of the third data selection circuit.