SEMICONDUCTOR STORAGE DEVICE AND METHOD FOR RELIEVING DEFECTIVE CELL

摘要

PURPOSE:To relieve a larger number of defective cells while the area expansion of a redundant circuit required for the relief of the defective cells is suppressed. CONSTITUTION:The memory cell array 5 of a mask ROM is divided into memory cell groups. A redundant circuit 10 is provided with data storing cell groups 2 which can store all data of the memory cell groups containing defective cells and a defective address storing cell 1 which stores the higher-order bit data (A9-A4) of addresses commonly given to all cells of the defective memory cell groups. When it is discriminated at a comparator circuit 3 that the higher-order bit of input address data coincides with the abovementioned stored data (A9-A4), redundant data are read out from the data storing cell groups 2 based on the lower-order bit of the address data and outputted through a switching circuit 4. Namely, all data of the defective memory cell groups are replaced with the redundant data. Therefore, numerous defective cells in the same memory cell group can be relieved by only enlarging the capacity of the data storing cell groups 2.