Disclosed herein is a device that responds to mat selection information, which is used to select one of memory mats, and selects at least one defective address from a plurality of defective addresses which are stored, for example, in a fuse circuit. When the access address information is coincident with a selected defective address, a redundant memory cell is accessed for reading or writing data in place of a normal memory cell. In a refresh operation, on the other hand, a column addressing, including the above replacement of a normal memory cell with a redundant memory cell, is deactivated.