Semiconductor memory devices

In a defect relieving technology which replaces defec­tive memory cells of a semiconductor memory device by spare memory cells, use is made of an associative memory (1). Ad­dress information of a defective memory cell is stored as a reference data of the associative memory (1), and new address information of a spare memory cell is written down as output data of the associative memory. A variety of improvements are made to the associative memory (1). For instance, a plurality of coincidence detection signal lines (16) of the associative memory (1) are divided into at least two groups, and one group among them is selected by switching means (5). Reference data of the associative memory (1) comprises three values consis­ting of binary information of "0" and "1", and don't care value "X". The associative memory further includes a plurality of electrically programable non-volatile semiconductor memory elements (39).