| 摘要 |
<p>PURPOSE:To improve the yield of a memory device by adding a redundant cell multiple switching circuit to a redundant cell selecting circuit. CONSTITUTION:A redundant cell selection control circuit is provided with the redundant cell selecting circuits 21, 34 and the redundant cell selection control circuit 41 inactivating the selective signal 35 of the redundant cell selecting circuit 21 is added to the circuits 21, 34. A defective cell is present in a main cell and the defective cell is switched to other redundant cell again when the defect is present in the switched redundant cell, as well in spite of switching the defective cell to the redundant cell. At this time, the simultaneous selection of the redundant cell is prevented by the redundant cell selection control circuit 41 and an access is allowed to only the redundant cell switched again. Thus, the relieved memory device is increased since the redundant cell is replaced to other redundant cell again even when the defective cell is contained in the replaced redundant cell and the yield is improved.</p> |
