DEFECT-RELIEVING CIRCUIT OF READ-ONLY MEMORY DEVICE

摘要

PURPOSE: To provide a mask ROM in which a redundant cell array can be constituted of cells in the same structure as a normal memory cell array, and integrative degree can be improved. CONSTITUTION: A memory cell array 10 and a redundant cell array 12 are formed by dividing one cell array by word line units, and a bit line is shared. The word line of the memory cell array 10 is driven by a line decoder 14, and the word line of the redundant cell array 12 is driven by a redundant line decoder 16. A redundant address decoder 26 stores the address signal of a line block including a defective NAND cell string of the memory cell array 10, and when a block selection address signal is the same as the stored defect address signal, a redundancy enable signal RE is outputted as a logic 1, and otherwise, it is outputted as a logic 0. The line decoder 14 and the redundant line decoder 16 are activated when the redundancy enable signal RE is the logic 0.