Double word line type dynamic RAM having redundant sub-array of cells

摘要

In a double word line type dynamic RAM, redundant memory cells to be substituted for defective cells are concentrated so as to form only one redundant sub-array in a row direction and in a column direction. The size of the redundant sub-array is made smaller than that of regular sub-arrays each composed of only regular cells. Although a minimum unit of cells to be replaced together becomes large in the double word line type dynamic RAM, the increase of the redundant memory cells can be effectively suppressed.