A semiconductor memory device includes a redundancy circuit having upper address bit input terminals receiving upper address bit, lower address bit input terminals receiving lower address bits, a regular memory cell array having a plurality of word lines and bit lines, and a plurality of memory cells are arranged at each intersection of the word and bit lines. A redundancy memory cell array is provided having a plurality of word and bit lines, and a plurality of memory cells are arranged at each intersection of the word and bit lines. The capacity of the redundancy memory cell array being smaller than the regular memory cell array. A first selection circuit selects a word or bit line in the regular memory cell array in accordance with the upper and lower address bits. A second selection circuit select a word or bit line in the redundancy memory cell array in accordance with the lower address bits. A redundancy address programming circuit programs the upper address bits corresponding to defective memory cells in the regular memory cell array. A control circuit compares the input upper address bits with the programmed upper address bits and controls the first and second selection circuits to inhibit the selection of the word or bit lines in the regular memory cell array. A predetermined word or bit line in the redundancy memory cell array is selected therefor when each of the input upper address bits coincides with each of the programmed upper address bits.

To achieve higher packaging density and one wafer level for a full-sized wafer memory, or wafer-scale integration memory system, the wafers are vertically stacked with each other at a predetermined interval. A packaging technique is improved in such a way that a memory system layout can be precisely realized and a precise through hole can be formed. Moreover, other chips are fixed on the wafer so as to achieve furthermore the high packaging density.

A remapping method and apparatus is employed by a memory controller system which includes a microprocessing section which couples to a memory section. The memory section includes a partially good bulk random access memory constructed from a plurality of bit wide chips containing a predefined small number of row or column faults randomly distributed. System columns of chips are organized into a plurality of groups or slices, each of which provide a different predetermined portion of the locations within the partially good bulk memory. A defective-free memory having substantially less capacity is similarly organized. Both memories couple to a static memory which is remapped under the control of the microprocessing section. Prior to remapping, the microprocessing section generates a "slice bit map" indicating the results of testing successive bit groups/slices within the bulk memory locations. Thereafter, the microprocessor section interprets the "slice bit map" and assigns column addresses in the static memory locations designating locations within the defect-free memory. The assignment is carried out in a predetermined manner according to fault category to maximize the use of all of the groups of bit locations within each defect free memory location thereby making storage available for remapping new faults.

To reduce waste and scrap of automotive electronic computer-type control apparatus constructed in hybrid technology on a substrate, due to malfunction, incorrect programming or desired change in data stored in the memory chip of a read-only memory (ROM) also applied in hybrid technology to the substrate, the substrate has a socket for a standard plug-insertable ROM or programmable ROM hard-wired connected thereto, the memory chip being enabled by application of a voltage applied to a circuit having a severable bridge (12) so that, upon severance of the bridge, the logic voltage applied to the chip will be of the "disable" value, permitting insertion of a standard ROM or PROM (16) into the additional socket (9) for supply of replacement data, the additional socket being hard-wired to a terminal (15) having an "enable" reference potential thereon. Preferably, isolating or decoupling resistors (3) are included in the address lines between the microprocessor (1) and the memory chip (5) to decouple the memory chip address input from the address inputs (8) of the additional socket and hence the additional memory (16 ).

A memory tester is disclosed for testing a matrix of memory elements, such matrix having spare rows and columns of memory elements to be used for repair of the memory under test. The memory tester tests the memory matrix to derive failure data and stores the failure data in corresponding rows and columns in a second memory matrix. Failure data in the second memory is scanned first by row and when the number of failures in any row exceeds the number of spare columns that row is flagged for replacement. Next, the columns of failure data are scanned and when the number of failures in any column exceeds the number of spare rows, that column is flagged for replacement. During the scan of the columns, previously flagged rows are masked such that failures which are to be repaired are not counted. Thereafter, with the flagged rows and column failures masked, the rows are again scanned and individual failures are flagged for replacement by remaining spare rows and columns until all spare rows and columns are used at which point detection of a subsequent failure flags the memory under test as non-repairable.