Abstract:
A semiconductor memory device and a failed cell address programming circuit usable therein. The semiconductor memory device as packaged includes a memory cell array having a plurality of memory cells accessed by an internal address, a plurality of redundant memory cells accessed by a failed cell address of a failed memory cell for repairing a failed memory cell, a comparator for comparing data output from the memory cells during testing the semiconductor memory device as packaged and generating a comparative correspondence signal, a mode setting register for storing an externally applied failed cell address programming control signal in response to a mode control signal, an address generating circuit for generating the internal address by buffering and latching an externally applied address, a failed cell address programming circuit for latching the internal address output from the address generating circuit in response to the failed cell address programming control signal when the comparative accordance signal indicates that a failed memory cell is detected and programming the failed cell address which is an address for accessing the failed memory cell; and a failed cell address decoding circuit for generating a redundant selection signal when the internal address output from the address generating circuit and the failed cell address output from the failed cell address programming correspond.

Description:
This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application 2002-6235 filed on Feb. 4, 2002, the entire contents of both of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a semiconductor memory device, and more particularly, to a failed cell address programming circuit and a method for programming a failed cell address for repairing a failed memory cell. 
     2. Description of Related Art 
     A semiconductor memory device is usually tested after it is packaged. When a damaged or failed memory cell is found, an address (herein after referred to as a “failed cell address”) for accessing the damaged or failed memory cell is stored in an additionally provided device. It is determined whether the failed memory cell can be repaired. If the failed memory cell can be repaired, the failed cell address stored in the additionally provided device is programmed into the semiconductor memory device by applying the failed cell address to a mode setting register. 
     FIG. 1 is a schematic block diagram of a conventional semiconductor memory device that is disclosed in Korean Patent Application No. 2000-57067 filed in the Korean Patent Office by the same assignee as the present invention. 
     As shown in FIG. 1, the conventional semiconductor memory device includes a memory cell array  10 , a column address decoder  12 , a row address decoder  14 , a sense amplifier  16 , a write amplifier  18 , a data input buffer  20 , a data output driver  22 , a data output buffer  24 , a mode setting resistor  26 , a failed cell address control signal generating circuit  28 , a column address buffer  30 , a row address buffer  32 , a repaired cell enable control signal generating circuit  34 , a repaired cell read/write control circuit  36 , a repaired cell  38 , switches  40 ,  41 , and a comparator  42 . 
     The operation of the conventional semiconductor memory device of FIG. 1 described below. The memory cell array  10  has a plurality of memory cells for storing data. The data is input to and output from the memory cells in response to a plurality of word line selection signals WL 1 -WLm from the row address decoder  14  and a plurality of column selection signals Y 1 -Yn from the column address decoder  12 ,. 
     The column address decoder  12  generates a plurality of column selection signals Y 1 -Yn (n signals) by decoding buffered address CAi, CAiB. 
     The row address decoder  14  generates a plurality of word line selection signals WL 1 -WLm (m signals) by decoding buffered row address RAj, RAjB. 
     The sense amplifier  16  amplifies data output from the memory cell array  10  or transferred from the switch  40  in response to the read enable signal CRE. 
     The write amplifier  18  amplifies buffered data output from the data input buffer  20  and outputs amplified data to be sent to the memory cell array  10 . 
     The data input buffer  20  buffers data DQ 1 -DQy and outputs the buffered data. The data output driver  22  drives the data amplified by the sense amplifier  16 . The data output buffer  24  buffers the data driven by the data output driver  22  and outputs buffered data DQ 1 -DQy. 
     The mode setting register  26  stores a parallel bit test control signal PBT and a failed cell address MRSk, applied externally through input pins (not shown) in response to a mode control signal MRS, and then outputs the parallel bit test control signal PBT and the failed cell address MRSk. 
     The failed cell address control signal generating circuit  28  generates a failed cell column address PCEi and a failed cell row address PREj in response to the failed cell address MRSk. 
     The column address buffer  30  buffers the column address of an externally supplied address Ak, applied from address input pins (not shown), latches the column address, and generates buffered column address CAi, CAiB. 
     The row address buffer  32  buffers the row address of the externally supplied address Ak, applied from the address input pins, latches the row address, and generates buffered row address RAj, RAjB. 
     The repaired cell enable control signal generating circuit  34  generates a repaired cell enable signal PS when the failed cell column address PCEi and the buffered column address CAi, CAiB correspond, and the failed cell row address PREj and the buffered row address RAj, RAjB correspond. 
     The repaired cell read/write control circuit  36  generates the repaired cell enable signal PS in response to a control command CONTi and a read command RE, or in response to a control command CONTi and a write command WE. The repaired cell enable signal PS generated by using the control command CONTi and the read command RE is used as a repaired cell read control signal CRE. The repaired cell enable signal PS generated by using the control command CONTi and the write command WE is used as a repaired cell write control signal CWE. 
     The repaired cell  38  latches the data. The switch  40  is turned on in response to the repaired cell read control signal CRE, thereby transferring the data stored in the repaired cell  38 . 
     The comparator  42  compares data output from the sense amplifier  16  in response to the parallel bit test control signal PBT and generates a comparison result signal. 
     The switch  44  is turned on in response to the repaired cell write control signal CWE and transfers the data output from the data input buffer  20 . 
     The conventional semiconductor memory device shown in FIG. 1 is electrically tested after it is packaged. After testing, when a failed memory cell is found, a failed cell address, namely, the address of a failed memory cell, is first stored in an external device. The external device programs the failed cell address into a failed cell address control signal generating circuit in the semiconductor memory device. When the address applied through the input pins of the semiconductor memory device during normal operation of the semiconductor memory device matches to the failed cell address, data can be input into or output from a repaired cell instead of the failed memory cell. 
     That is, when the conventional semiconductor memory device as packaged has a failed memory cell, the address of the failed cell is first stored in the external device, and then the address of the failed cell is programmed into the semiconductor memory device from the external device during repair of the semiconductor memory device. 
     Accordingly, the conventional semiconductor memory device uses an expensive external device to temporarily store the failed cell address during testing and repairing the packaged semiconductor memory device. As a result, the cost of testing of the semiconductor memory device is increased. 
     The operation of programming the failed cell address in the conventional semiconductor memory device is described below referring to FIG.  2 . 
     A tester inputs the mode control signal MRS along with the parallel bit test control signal PBT into the semiconductor memory device (Step  100 ). The parallel bit test control signal PBT applied to the semiconductor memory device is stored in the mode setting register  26 . 
     A parallel bit testing operation is performed on the semiconductor memory device in response to the parallel bit test control signal PBT (Step  110 ). The parallel bit testing operation includes storing test data for testing the memory cell array  10  in the semiconductor memory device and reading the test data stored in the memory cell array  10  in parallel. The test data output from the memory cell array  10  are transmitted to the tester by a comparator  42 . 
     The tester determines whether the memory cell array  10  being tested is normal (Step  120 ). When the test data transmitted to the tester indicates comparative consistency, the corresponding memory cell array  10  is determined to be normal, while when the test data indicates comparative inconsistency, the corresponding memory cell array  10  is determined to be abnormal or failed. 
     If the tester indicates that the tested memory cell array  10  is abnormal or failed, an address of a failed memory cell referred to as a failed cell address is stored in an external device (Step  130 ). 
     When the tester indicates that the tested memory cell array  10  is normal in step  120 , it is determined whether the parallel bit testing operation has been performed on all cells of the memory cell array (Step  140 ). 
     If no in step  140 , steps  110 - 130  are repeated, while if yes, in step  140 , the tester determines whether the failed memory cells can be repaired (Step  150 ). 
     When the tester determines that the failed memory cells can be repaired, the mode control signal MRS and the failed cell address are input to the semiconductor memory device from the external device (Step  160 ). The failed cell address is stored in the mode setting register  26  in response to the mode control signal and the failed cell address is written into a failed cell address control signal generating circuit  28 . 
     When it is determined that the failed memory cell can not be repaired, the test completed semiconductor memory device is discarded (Step  210 ). 
     After the failed cell address is programmed into the failed cell address control signal generating circuit  28  in the semiconductor memory device, the mode control signal MRS and the parallel bit test control signal PBT are input again to the corresponding semiconductor memory device that has been repaired (Step  170 ). 
     The repaired semiconductor memory device again undergoes the parallel bit testing in response to the parallel bit test control signal PBT (Step  180 ). 
     The tester determines whether the parallel bit testing for all memory cell arrays in the repaired semiconductor memory device is completed (Step  190 ). 
     If the tester indicates that the parallel bit testing is not completed, steps  180 - 190  are repeated, and if the parallel bit testing is completed, the tester determines whether the repaired semiconductor memory device is normal or not (Step  200 ). 
     When the tester determines that the repaired semiconductor memory device is normal, the repaired semiconductor device is commercialized. 
     As discussed above, an expensive external device may be used for testing and repairing a conventional semiconductor memory device. Therefore, the cost of testing the semiconductor memory device may be increased. 
     SUMMARY OF THE INVENTION 
     In an exemplary embodiment, the present invention is directed to a semiconductor memory device capable of being repaired without using an additional external device during testing and repairing the packaged semiconductor memory device. 
     In an exemplary embodiment, the present invention is directed to a failed cell address programming circuit employed in a semiconductor memory device for programming an address of a failed memory cell into the semiconductor memory device. 
     In an exemplary embodiment, the present invention is directed to a method of programming the failed cell address into the packaged semiconductor memory device. 
     In an exemplary embodiment, the present invention is directed to a semiconductor memory device, comprising a memory cell array having a plurality of memory cells accessed by an internal address; a plurality of redundant memory cells accessed by a failed cell address of a failed memory cell, the redundant memory cells being used for repairing the failed memory cell; a comparator for comparing data output from the memory cells during testing the semiconductor memory device as packaged and for generating a comparative output signal; a mode setting register for storing a failed cell address programming control signal in response to a mode control signal; an address generating circuit for generating the internal address by buffering and latching an externally applied address; a failed cell address programming circuit for latching the internal address output from the address generating circuit in response to the failed cell address programming control signal when the comparative output signal indicates that a failed memory cell is detected in the semiconductor memory device and programming the latched internal address as the failed cell address; and a failed cell address coding circuit for generating a redundant memory cell selection signal when the internal address output from the address generating circuit and the failed cell address output from the failed cell address programming circuit correspond, wherein the redundant memory cell is accessed in response to the redundant memory cell selection signal. 
     In an exemplary embodiment, the present invention is directed to a failed cell address programming circuit of a semiconductor memory device having a memory cell array having a plurality of memory cells accessed by an internal address, a plurality of redundant memory cells accessed by a failed cell address of a failed memory cell, a comparator for generating a comparative output signal after comparing data output from the memory cell array during testing the semiconductor memory device as packaged and an address generator for generating the internal address by buffering and latching an externally applied address, said failed cell address programming circuit comprising a mode setting register for storing a failed cell address latching control signal and a programming control signal which are externally applied in response to a mode control signal; failed cell address latching means for latching address output from the address generator in response to the failed cell address latching control signal when the comparative output signal indicates that at least one of the memory cells has failed; and failed cell address programming means for programming the address output from the failed cell address latching means in response to the programming control signal. 
     In an exemplary embodiment, the present invention is directed to a method for programming a failed cell address of a failed memory cell of a memory cell array with a plurality of memory cells accessed by an internal address, a plurality of redundant memory cells accessed by the failed cell address, a comparator for generating a comparative output signal after comparing data output from the memory cell array during testing of the semiconductor memory device as packaged and an address generator for generating the internal address by buffering and latching an externally applied address, said method comprising: latching the internal address output from the address generator in response to the failed cell address latching control signal when the comparative output signal indicates that at least one memory cell has failed; and programming the internal address which is latched in response to the programming control signal. 
     In an exemplary embodiment, the present invention is directed to a semiconductor memory device, comprising: a failed cell address programming circuit for latching an internal address from an address generating circuit in response to a failed cell address programming control signal when a failed memory cell is detected and programming the latched internal address as the failed cell address; and a failed cell address coding circuit for generating a redundant memory cell selection signal when an internal address and the failed cell address output from the failed cell address programming circuit correspond, wherein a redundant memory cell is accessed in response to the redundant memory cell selection signal. 
     In an exemplary embodiment, the present invention is directed to a failed cell address programming circuit, comprising: failed cell address latching means for latching an address output from an address generator in response to a failed cell address latching control signal when at least one of the memory cells has failed; and failed cell address programming means for programming the address output from the failed cell address latching means in response to the programming control signal. 
     In an exemplary embodiment, the present invention is directed to a method for programming a failed cell address of a failed memory cell of a memory cell array with a plurality of memory cells and a plurality of redundant memory cells accessed by the failed cell address, said method comprising: latching an internal address output from an address generator in response to a failed cell address latching control signal when at least one memory cell has failed; and programming the internal address which is latched in response to the programming control signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which like reference numerals denote like parts, and in which: 
     FIG. 1 is a schematic block diagram of a semiconductor memory device in accordance with the conventional art; 
     FIG. 2 is a flow chart showing a method of testing and repairing the semiconductor memory device in accordance with the conventional art; 
     FIG. 3 is a block diagram of a semiconductor memory device in accordance with an exemplary embodiment of the present invention; 
     FIG. 4 is an exemplary circuit diagram of a failed cell address latching circuit illustrated in FIG. 3 in accordance with an exemplary embodiment of the present invention; 
     FIG. 5 is another exemplary circuit diagram of the failed cell address latching circuit illustrated in FIG. 3, in accordance with an exemplary embodiment of the present invention; 
     FIG. 6 is a circuit diagram of a failed cell address programming circuit illustrated in FIG. 3, in accordance with an exemplary embodiment of the present invention; 
     FIG. 7 is a circuit diagram of a failed cell address coding circuit illustrated in FIG. 3, in accordance with an exemplary embodiment of the present invention; and 
     FIG. 8 is a flow chart showing a method of programming the failed cell address in a semiconductor memory device in accordance with an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to exemplary embodiments of the present invention, example of which is illustrated in the accompanying drawings. 
     FIG. 3 is a block diagram of a semiconductor memory device in accordance with an exemplary embodiment of the present invention. 
     As shown in FIG. 3, the semiconductor memory device is packaged and includes a memory cell array  50  having a normal memory cell array  50 - 1  and a column redundant memory cell array  50 - 2 . The semiconductor memory device further includes a row address decoder  52 , a column address decoder  54 , a sense amplifier  58 , a write amplifier  60 , a data input buffer  62 , a data output driver  64 , a data output buffer  66 , a mode setting register  68 , a column address buffer  70 , a row address buffer  72 , a failed cell latching circuit  74 , a failed cell programming circuit  76 , a failed cell address coding circuit  78  and a comparator  80 . 
     The memory cell array  50 , the row address decoder  52 , the column address decoder  54 , the sense amplifier  58 , the write amplifier  60 , the data input buffer  62 , the data output driver  64 , the data output buffer  66  and the comparator  80  have substantially the same function as the corresponding elements referred as the same name in FIG.  1 . Accordingly, explanation of the function thereof will be omitted. 
     The mode setting register  68  receives externally applied signals through address input pins of the semiconductor memory device in response to a mode control signal MRS, and generates a program control signal EFC, a failed cell address latching control signal FAL and a parallel bit test control signal PBT. 
     The column address buffer  70  buffers and latches a column address of an externally supplied address Ak, and then generates a buffered column address CAi, CAiB. The row address buffer  70  buffers and latches a row address of an externally supplied address Ak, and then generates a buffered row address RAi, RAiB. 
     The failed cell address latching circuit  74  outputs the buffered column address CAi, CAiB in response to an output signal of the comparator  80  and the failed cell address latching control signal FAL. The failed cell address programming circuit  76  programs the failed cell address output from the failed cell address latching circuit  74  in response to the program control signal EFC. 
     The failed cell address coding circuit  78  generates a redundant column selection signal RY when the programmed cell address corresponds to the buffered column address CAi, CAiB. The column address decoder  54  may be disabled in response to the redundant column selection signal RY 
     In the semiconductor memory device of FIG. 3, the memory cell array  50 - 1  has a plurality of memory cell columns and each of the columns is accessed by a column selection signal of the column selection signals Y 1 -Yn. When the semiconductor memory device has a column including at least one failed memory cell, the column including the failed memory cell is replaced with a redundant column that is comprised of a plurality of redundant memory cells  50 - 2  and accessed by the redundant column selection signal RY. That is, the semiconductor memory device is repaired column by column. In another exemplary embodiment, the semiconductor memory device can be repaired cell by cell. 
     FIG. 4 is an exemplary circuit diagram of the failed cell address latching circuit  74  in an exemplary embodiment of the present invention. As shown in FIG. 4, each of the failed cell address latching circuits  74 - 1 - 74 -i comprises a latching control signal generating circuit  75  comprised of a NAND gate NA 1  and an inverter I 1  and a latching element L comprised of a CMOS transmitting gate C 1 , an inverter I 2  and inverters I 3  and I 4 . 
     The latching control signal generating circuit  75  generates a logic “high” level of latching control signal when an output signal COUT of the comparator  80  and the failed cell latching control signal FAL have a logic “high” level. 
     The CMOS transmitting gate C 1  is turned on in response to a logic “high” level of the failed cell address latching control signal FAL, and transfers the failed cell address CA 1 -CAi. The latching element L in each of the address latching circuits  74 - 1 - 74 -i latches an output signal of the CMOS transmitting gate C 1  and generates the failed cell address output signals PCA 1 -PCAi. 
     FIG. 5 is another exemplary circuit diagram of the failed cell address latching circuit  74  in accordance with an exemplary embodiment of the present invention. As shown in FIG. 5, the failed cell address latching circuit further comprises a PMOS transistor in addition to the elements shown in FIG.  4 . 
     The elements designated by like reference numbers in FIG.  4  and FIG. 5 are like elements and therefore operated in substantially the same way. Accordingly, a discussion thereof in conjunction with FIG. 5 is omitted. 
     The PMOS transistor P 1  is turned on when an output signal of the NAND gate NA 1  is a logic “low” level, thereby transferring a logic “high” level signal. Then, the transferred logic “high” level signal is input to a tester via a pin of the semiconductor memory device, whereby the tester can detect that the failed cell address latching circuit is being used. That is, the tester determines whether the semiconductor memory device can be repaired using a combined signal that is transmitted by the PMOS transistor P 1  and generated by combining the failed cell address latching control signal and the comparative output signal. Accordingly, the combined signal may be considered a repair start signal. 
     FIG. 6 is an exemplary circuit diagram of the failed cell address programming circuit  76  in accordance with an exemplary embodiment of the present invention. As shown in FIG. 6, the failed cell address programming circuit includes a plurality of failed cell control signal generators  76 - 1 - 76 -i. Each of the failed cell control signal generators  76 - 1 - 76 -i includes a CMOS transmitting gate C 2 , inverters I 5 , I 6 , I 7  and an electrical fuse circuit EF each of which is comprised of NMOS transistors N 1 , N 2 , N 3 , N 4 , N 5 , PMOS transistors P 2 , P 3  and fuses F 1 , F 2 . In FIG. 6, the fuse F 2  has relatively lower resistance than that of the fuse F 1 . 
     Operation of the failed cell address programming circuit  76 - 1  is discussed below. When a logic “high” level of the programming control signal EFC is applied to the failed cell control signal generator  76 - 1 , the CMOS transmitting gate C 2  is turned on. At this time, when a logic “low” level of the failed cell output signal PCA 1  is input to the failed cell control signal generator  76 - 1 , the NMOS transistor N 1  is turned off, so that the fuse F 1  is not blown. Then, the NMOS transistors N 2 , N 5  are turned on in response to the logic “high” level of the programming control signal EFC, and a voltage potential at a node A becomes slightly greater than that at a node B. Accordingly, the output signal OPCA 1  having a logic “low” level is output from the failed cell control signal generator  76 - 1  through the inverters I 6 , I 7 . 
     When a logic “high” level of the programming control signal EFC and a logic “high” level of the failed cell output signal PCA 1  are applied to the failed cell control signal generator  76 - 1 , the NMOS transistor N 1  is turned on and the fuse F 1  is blown. Then, the NMOS transistors N 2 , N 5  are turned on in response to the logic “high” level of the programming control signal EFC, and a voltage potential at a node A is lowered to be slightly lower than that at a node B. Accordingly, the output signal OPCA 1  having a logic “high” level is output from the failed cell control signal generator  76 - 1  through the inverters I 6 , I 7 . 
     That is, the failed cell address programming circuits  76 - 1 - 76 -i generate a logic “low” level of the output signals OPCA 1 -OPCAi, respectively in response to a logic “high” level of the programming control signal EFC when a logic “high” level of the failed cell address output signals PCA 1 -PCAi are transmitted thereto, respectively. Further, the failed cell address programming circuits  76 - 1 - 76 -i generate a logic “high” level of the output signals OPCA 1 -OPCAi, respectively in response to a logic “high” level of the programming control signal EFC when a logic “low” level of the failed cell address output signals PCA 1 -PCAi, respectively, are transmitted thereto. 
     As discussed above, a level of the output signals OPCA 1 -OPCAi output from the failed cell control signal generator  76 - 1 - 76 -i may be repaired. 
     FIG. 7 is a circuit diagram of the failed cell coding circuit  78  in accordance with an exemplary embodiment of the present invention. As shown in FIG. 7, the failed cell coding circuit  78  includes a redundant column selection signal generating circuit  79  including a NAND gate N 5  and an inverter I 9 , and a failed cell address coder  78 - 1 - 78 -I, each having an inverter I 8  and NAND gates NA 2 , NA 3 , NA 4 . 
     When the output signal OPCA 1  is a logic “high” level, the NAND gate N 2  inverts and outputs the buffered column address CA 1 , and the NAND gate N 3  inverts and outputs an inverted buffered column address CAIB. The NAND gate N 4  NANDs output signals of the NAND gates NA 2  and NA 3  and generates a comparative output signal COM 1 . 
     As a result, when the output signal OPCA 1  is a logic “high” level and the buffered column address PCA 1  is a logic “high” level, the comparative output signal COM 1  has a logic “high” level. Further, when the output signal OPCA 1  is a logic “high” level and the buffered column address PCA 1  is a logic “low” level, the comparative output signal COM 1  has a logic “low” level. 
     When the output signal OPCA 1  is a logic “low” level, the NAND gate NA 2  inverts and outputs the buffered inverted column address CA 1 B, and the NAND gate NA 3  inverts and outputs the buffered column address CA 1 . The NAND gate NA 4  NANDs output signals of the NAND gates NA 2  and NA 3  and generates the comparative output signal COM 1 . 
     As a result, when the output signal OPCA 1  is a logic “low” level and the buffered column address CA 1  is a logic “high” level, the comparative output signal COM 1  has a logic “low” level. When the output signal OPCA 1  is a logic “low” level and the buffered column address CA 1  is a logic “low” level, the comparative output signal COM 1  has a logic “high” level. 
     The redundant column selection signal generating circuit  79  generates a redundant column selection signal RY with a logic “high” level when all of the comparative output signals COM 1 -COMi have logic “high” levels, and generates the redundant column selection signal RY with a logic “low” level when at least one comparative output signal of the comparative output signals COM 1 -COMi is has a logic “low” level. 
     That is, the failed cell address is directly programmed in the packaged semiconductor memory device without using an external device that is used for temporarily storing the failed cell address for repairing the packaged conventional semiconductor memory device. 
     A method of programming the failed cell address into the semiconductor memory device in accordance with an exemplary embodiment of the present invention will be described below with reference to FIG.  8 . 
     A tester inputs a mode control signal MRS and a parallel bit test control signal PBT to a packaged semiconductor memory device (Step  300 ). The parallel bit test control signal PBT is stored in a mode setting register  68  in the packaged semiconductor memory device in response to the mode control signal MRS. A parallel bit test operation is performed against the packaged semiconductor memory device (Step  310 ). 
     During the parallel bit test operation, the tester determines whether a comparator  80  in the packaged semiconductor memory device outputs logic “high” level of an output signal (Step  320 ). That is, the tester determines whether the packaged semiconductor memory device has a failed memory cell using the output signal of the comparator  80 . 
     When the comparator  80  outputs logic a “low” level of the output signal in the step  320 , the tester determines in step  330  whether the test for all memory cells in the packaged semiconductor memory device is complete. If not, at step  330 , steps  310 - 320  are repeated. If yes, in step  330 , step  410  is performed. 
     When the comparator  80  outputs logic the output signal in step  320  with a “high” level, the tester determines whether the packaged semiconductor memory device can be repaired (Step  340 ). 
     The semiconductor memory device can be repaired when the failed cell latching control signal generated by the failed cell address latching circuit shown in FIG. 5 transits from logic a “low” level to a logic “high” level. If the semiconductor memory device has the failed cell address latching circuit shown in FIG. 4, step  320  may be omitted. 
     If the packaged semiconductor memory device can not be repaired in step  340 , the test completed semiconductor memory device is discarded and if the packaged semiconductor memory device can be repaired in step  340 , the tester inputs the mode control signal MRS, the failed cell address latching control signal FAL and a programming control signal EFC to the semiconductor memory device (Step  350 ). The mode setting register  68  in the semiconductor memory device receives the failed cell address latching control signal FAL and the programming control signal EFC. 
     The failed cell address latching circuit  74  in the packaged semiconductor memory device programs the failed cell address in response to the failed cell address latching control signal FAL (Step  360 ). The failed cell address programming circuit  76  programs the failed cell address in response to the programming control signal EFC (Step  370 ). The tester transmits the mode control signal MRS and the parallel bit test control signal PBT to the semiconductor memory device (Step  380 ). The parallel bit test operation for the repaired semiconductor memory device is performed in response to the parallel bit test control signal PBT (Step  390 ). 
     It is then determined whether the parallel bit test operation for all memory cells in the repaired semiconductor memory device is completed (Step  400 ). If not, step  390  is repeated. If yes in step  400 , it is determined whether the repaired semiconductor memory device is normal (Step  410 ). If yes in step  410 , the test completed semiconductor memory device is commercialized (Step  430 ) and if not, the test completed semiconductor is discarded. (Step  420 ) 
     As a result, if the semiconductor memory device in accordance with exemplary embodiments of the present invention has a failed memory cell, an address to access the failed memory cell (a failed cell address), is stored in a failed cell address latching circuit  74  in the semiconductor memory device and then programmed in the failed cell programming circuit  76 . 
     The exemplary embodiments of the present invention as discussed above disclose repairing the semiconductor memory device column by column but exemplary embodiments of the present invention may also include repairing the semiconductor memory device row by row or cell by cell. 
     Further, the structure of the redundant memory cell of the exemplary embodiments of the present invention described above is not limited to the structure discussed above, but may be modified as would be known to one of ordinary skill in the art. 
     The exemplary embodiments of the present invention describe repairing one bit of a failed memory cell but the present invention may be also applied to a method of repairing a plurality of bits of failed memory cells. 
     Further, exemplary embodiments of the present invention may be applied to a semiconductor memory device having a plurality of memory cell arrays, each of which has a plurality of memory banks, wherein the parallel bit test is performed for a plurality of memory banks at the same time. 
     While the invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.