Abstract:
Disclosed is a semiconductor memory device and a data read method thereof. The semiconductor memory device comprises a memory cell array comprising a plurality of sub-arrays, said sub-arrays comprising a plurality of memory cells and repeaters, wherein each of said memory cells is connected to a corresponding pair of read word lines, a corresponding pair of read bitlines, a corresponding pair of write word lines, and a corresponding pair of write bitlines, and wherein each of said repeaters is connected to said corresponding pair of read bitlines of each said memory cell and a corresponding pair of common main read bitlines so as to transmit read data from said corresponding pair of read bitlines to said corresponding pair of common main read bitlines in response to an applied enable control signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Patent Application No. 2000-69234, filed on Nov. 21, 2000, the disclosures of which are incorporated by reference herein in their entirety.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention refers to a semiconductor memory device and, more particularly, to a read bitline arrangement comprising multi data read/write ports. In addition, a data read method utilizing the device is also described.  
           [0004]    2. Description of Related Art  
           [0005]    In general, a pair of bitlines connected to a cell of memory cell array in a semiconductor memory device reads data in reading operations and writes data in writing operations. Therefore, because the semiconductor memory device cannot perform both data reading and data writing operations simultaneously, the typical semiconductor memory device comprises unique data read/write ports in transmitting data.  
           [0006]    On the other hand, memory devices having multiple data read and write ports provide separate read bitlines and write bitlines to read and write data and thereby permit read and write operations to be performed independently.  
           [0007]    [0007]FIG. 1 is a block diagram illustrating an example of a conventional semiconductor memory device with multiple read ports and write ports.  
           [0008]    The conventional semiconductor memory device of FIG. 1 includes memory cell array  10 , first and second row read address decoders  12 - 1  and  12 - 2 , first and second row write address decoders  14 - 1  and  14 - 2 , first and second column read multiplexers  16 - 1  and  16 - 2 , first and second column write multiplexers  18 - 1  and  18 - 2 , and first and second column read address decoders  20 - 1  and  20 - 2 . Further, the conventional semiconductor memory device of FIG. 1 also includes first and second column write address decoders  22 - 1  and  22 - 2 , first and second write drivers  24 - 1  and  24 - 2 , first and second data input buffers  26 - 1 , and  26 - 2 ,and first and second data output buffers  28 - 1  and  28 - 2 .  
           [0009]    In FIG. 1, the memory cell array  10  comprises (1) multiple pairs of read bitlines rb 11  and rb 12 , rb 2 l and rb 22 , . . . , rbk 1  and rbk 2 , (2) multiple pairs of read word lines RWL 11  and RWL 12 , RWL 21  and RWL 22 , . . . , RWLm 1  and RWLm 2 , (3) multiple pairs of write bitlines wb 11  and wb 12 , wb 2 l and wb 22 , . . . , wbk 1  and wbk 2 , (4) multiple pairs of write word lines WWL 11  and WWL 12 , WWL 21  and WWL 22 , . . . , WWLm 1  and WWLm 2 , and a plurality of memory cells MC connected to those corresponding four types of pairs of lines.  
           [0010]    In response to both signals applied from write word lines WWL 11 , WWL 21 , . . . , WWWm 1 , and write control signals wc 11 ,wc 21 , . . . , wck 1 , each of a plurality of memory cells MC store data from each of corresponding write bitlines wb 11 , wb 21 , . . . , wbk 1  . In a similar way, in response to both signals applied from write word lines WWL 12 , WWL 22 , . . . , WWWm 2 , and write control signals wc 12 ,wc 22 , . . . , wck 2 , each of the memory cells MC store data from each of corresponding write bitlines wb 12 , wb 22 , . . . , wbk 2 . Even though not illustrated in FIG. 1, write control signals wc 11 , wc 21 , . . . , wck 1  are generated by buffering and delaying first column-selecting control signals WY 11 , WY 12 , . . . , WY 18 . Write control signals wc 12 , wc 22 , . . . , wck 2  are generated by buffering and delaying second column-selecting control signals WY 21 , WY 22 , . . . , WY 28 .  
           [0011]    The device of FIG. 1 includes two data read ports and two data write ports.  
           [0012]    The functions of the blocks in the semiconductor memory device of FIG. 1 are as follows:  
           [0013]    The first row read address decoder  12 - 1  decodes a first row read address FRRA, and selects one of first read word lines RWL 11 , RWL 21 , . . . , RWLm 1 . The second row read address decoder  12 - 2  decodes a second row read address SRRA and selects one of second read word lines RWL 21 , RWL 22 , . . . , RWLm 2 . The first row write address decoder  14 - 1  decodes a first row write address FRWA and selects one of first write word lines WWL 11 , WWL 21 , . . . , WWLm 1 . The second row write address decoder  14 - 2  decodes a second row write address SRWA and selects one of second write word lines WWL 21 , WWL 22 , . . . , WWLm 2 . The first column read multiplexer  16 - 1  selectively outputs data through read bitlines rb 11 , rb 21 , . . . , rbm 1 . In this case, when a multiplexer is a two-input type, the multiplexer selects a read data transmitted from a selected line between two adjacent read bitlines and outputs the selected read data. In a similar way, the multiplexer of a four-input type selects a read data transmitted from a selected line among four adjacent read bitlines and outputs the selected read data. Therefore, the multiplexer of an eight-input type selects a read data transmitted from a selected line among eight adjacent read bitlines and outputs the selected read data. FIG. 1 illustrates a semiconductor memory device with an eight-input multiplexer, meaning that, in response to the column-selecting control signals RY 11 , RY 12 , . . . , RY 18 , the multiplexer of the eight-input type selects a read data transmitted from a selected line among eight adjacent read bitlines and outputs the selected read data. The second column read multiplexer  16 - 2  outputs a read data selectively according to the input type of the multiplexer in the same way as the first column read multiplexer  16 - 1  selectively.  
           [0014]    The first column write multiplexer  18 - 1  puts data to write bitlines wb 11 , wb 21 , . . . , wbm 1  and the second column write multiplexer  18 - 2  puts data to write bitlines wb 12 , wb 22 , . . . , wbm 2 . In response to column-selecting control signals WY 11 , WY 12 , . . . WY 18  and WY 21 , WY 22 , . . . , WY 28 , the first and the second column write multiplexers  18 - 1  and  18 - 2  apply the data to a selected one line of a bitline pair in a manner analogous to the read operations of the first and the second column read multiplexers  16 - 1  and  16 - 2 .  
           [0015]    The first column read address decoder  20 - 1  decodes three bits of the first column read address FCRA and generates eight column-selecting control signals RY 11 , RY 12 , . . . , RY 18 . The second column read address decoder  20 - 2  decodes three bits of the second column read address SCRA and generates eight column-selecting control signals RY 21 , RY 22 , . . . , RY 28 . The first column write address decoder  22 - 1  decodes three bits of the first column write address FCWA and generates eight column-selecting control signals WY 11 , WY 12 , . . . , WY 18 . The second column write address decoder  22 - 2  decodes three bits of the second column write address SCWA and generates eight column-selecting control signals WY 21 , WY 22 , . . . , WY 28 .  
           [0016]    The first write driver  24 - 1  drives the first write data and the second write driver  24 - 2  drives the second write data through the write multiplexers. The first data input buffer  26 - 1  buffers first input data Din 1  from the outside and generates a first write data. The second data input buffer  26 - 2  buffers second input data Din 2  and generates a second write data. The first data output buffer  28 - 1  buffers first read data from the first column read multiplexer  16 - 1  and generates a first output data Dout 1 . The second data output buffer  28 - 2  buffers second read data from the second column read multiplexer  16 - 2  and generates a second output data Dout 2 .  
           [0017]    Operations of the semiconductor memory device of FIG. 1 are as follows:  
           [0018]    An applied write enable signal (not shown) enables a write operation and then the write operation is executed when a first write address and a first input data are applied on the rising edge of a clock signal.  
           [0019]    An example of a write operation may be illustrated with the assumption that the first input data Din 1  is “00 . . . 0”, the first row write address FRWA is “00 . . . 0”, and the first column write address FCWA is “000”.  
           [0020]    The first data input buffer  26 - 1  buffers and outputs the first input data Din 1  “00 . . . 0”. The first write driver  24 - 1  drives the output data of the first data input buffer  26 - 1 . The first column write address decoder  22 - 1  decodes the first column write address FCWA as “000” and generates the first column-selecting control signal WY 11  at logical “high” while the other first column-selecting control signal WY 12 , . . . , WY 18  are in “low” logic levels. The first row write address decoder  14 - 1  decodes the first row write address FRWA as “00 . . . 0” and selects the first write word line WWL 11  by raising it to logical “high”.  
           [0021]    In response to the first column-selecting control signal WY 11  being at logical “high”, the first column write multiplexer  18 - 1  outputs the data from the first data input buffer  26 - 1  to the adjacent eight write bitlines wb 11 , wb 91 , . . . , wb(k−8) 1  among the first write bitlines wb 11 , wb 21 , . . . , wbk 1 . The first column write multiplexer  18 - 1  also selects write control signals wc 11 ,wc 91 , . . . , wc(k−8) 1  in response to the column-selecting control signal WY 11  being at logical “high”. Then, the first write data is stored in memory cell MC connected to both the first write word line WWL 11  and the adjacent eight write bitlines wb 11 , wb 91 , . . . , wb(k−8) 1 .  
           [0022]    Writing operations of the second input data Din 2  are performed by the second row write address decoder  14 - 2 , the second data input buffer  26 - 2 , the second write driver  24 - 2 , the second column write address decoder  22 - 2 , and the second column write multiplexer  18 - 2 . Each of writing operations of the first input data Din 1 , writing operations of the second input data Din 2 , reading operations of the first output data Dout 1 , and reading operations of the second output data Dout 2  are performed independently and individually.  
           [0023]    An applied read enable signal (not shown) initiates a read operation. The following example illustrate read operations on the assumption that the first row read address FRRA is “00 . . . 1” and the first column read address FCRA is “001”.  
           [0024]    The first row read address decoder  12 - 1  decodes the first row read address FRRA as “00 . . . 1” and selects the first read word line RWL 21 , bringing it to logical “high”. Then, the first read data from the memory cell MC connected to the first read word line RWL 21  is outputted to the first read bitlines rb 11 , rb 21 , . . . , rbk 1 . The first column read address decoder  20 - 1  decodes the first column read address FCRA as “001” and generates the first column-selecting signal RY 12  of “high” logic level while the first column read address decoder  20 - 1  generates a “low” logic level in the other of the first column-selecting signals RY 11 , . . . , RY 18 . In response to the first column-selecting signal RY 12  being at a “high” logic level, the first column read multiplexer  16 - 1  selects and outputs data from the adjacent eight bitlines rb 21 , rb 101 , . . . , rb(k−7) 1  from the set of first read bitlines rb 11 , rb 21 , . . . , rbk 1 . The first data output buffer  28 - 1  buffers data from the first column read multiplexer  16 - 1  and outputs the data through the first output data Dout 1 . Writing operations of the second output data Dout 2  are performed by the second row read address decoder  12 - 2 , the second column read multiplexer  16 - 2 , the second column read address decoder  20 - 2 , and the second data output buffer  28 - 2 . Reading operations in the second output data Dout 2 , reading operations in the first output data Dout 1 , writing operations of the first input data Din 1 , and writing operations in the second input data Din 2  are performed independently and individually.  
           [0025]    However, the semiconductor memory device of FIG. 1 cannot perform both read operations and write operations in the same address simultaneously without data contention. What is needed is a device and method that can both read and write from the same address substantially simultaneously.  
           [0026]    A Referring to FIG. 2 there is shown a circuit diagram of a typical memory cell MC that may also be utilized in the invention. The memory cell MC shown as an example in the drawing is that connected to read word lines RWL 11  and RWL 12 , write word lines WWL 11  and WWL 12 , read bitlines rb 11  and rb 12 , and write bitlines wb 11  and wb 12 .  
           [0027]    The memory cell MC of FIG. 2 comprises NMOS transistors N 1 , N 2 , N 5 , N 6 , N 7 , and N 8 , inverter INV 2 , which itself comprises NMOS transistor N 3  and PMOS transistor P 1 , and inverter INV 3 , which itself comprises NMOS transistor N 4  and PMOS transistor P 2 .  
           [0028]    Inverters INV 2  and INV 3  latch data between nodes Nd 1  and Nd 2 . NMOS transistors N 1  and N 2  transmit read data to corresponding read bitlines rb 11  and rb 12  in response to selecting signals in corresponding read word lines RWL 11  and RWL 12 , respectively. The inverter INV 1  inverts the read data and transmits it to node Nd 3 . NMOS transistors N 5  and N 6  transmit write data to node Nd 2  in response to selecting signals in corresponding write word lines WWL 11  and WWL 12 , respectively. NMOS transistors N 7  and N 8  transmit write data of the corresponding write bitlines wb 11  and wb 12  to NMOS transistors N 5  and N 6  in response to corresponding write control signals wc 11  and wc 21 .  
           [0029]    As the capacity of memory cell array  10  increases, the greater are the number of memory cells are arranged in the column direction. In such case, the length of the first read bitlines rb 11 , rb 12 , . . . , rbk 1 , the second read bitlines rb 12 , rb 22 , . . . , rbk 2 , the first write bitlines wb 11 , wb 12 , . . . , wbk 1 , and the second write bitlines wb 12 , wb 22 , . . . , wbk 2  is increased so that the number of NMOS transistors N 1  and N 2 , N 7  and N 8  connected to those corresponding lines can be increased, which finally results in an increase in line load capacitances, which slows down speeds in both read and write operations, and raises the consumption voltages in the memory cells.  
           [0030]    In addition, transmission gates transmitting read data, such as transistors N 1  and N 2 , show good transmission performance for logical “low”, but poor transmission performance for logical “high”. A way to improve transmission performance in “high” logic level data is to increase both the size of NMOS transistors N 1  and N 2 , and the size of inverter INV 1 . However, increasing the size of NMOS transistors N 1  and N 2 , and the size of inverter INV 1  results in increased line load capacitances.  
           [0031]    Enlarging the sizes of the first and the second write drivers  24 - 1  and  24 - 2  can improve write speed, but at the cost of increasing line load capacitances in the first bitlines wb 11 , wb 21 , . . . , wbk 1  and in the second write bitlines wb 12 , wb 22 , . . . , wbk 2 .  
           [0032]    What is needed is a semiconductor memory device with improved speeds in data read/write operations regardless of increases in bitline load capacitances.  
         SUMMARY OF THE INVENTION  
         [0033]    Disclosed is a semiconductor memory device comprising a memory cell array comprising a plurality of sub-arrays, said sub-arrays comprising a plurality of memory cells and repeaters, wherein each of said memory cells is connected to a corresponding pair of read word lines, a corresponding pair of read bitlines, a corresponding pair of write word lines, and a corresponding pair of write bitlines, and wherein each of said repeaters is connected to said corresponding pair of read bitlines of each said memory cell and a corresponding pair of common main read bitlines so as to transmit read data from said corresponding pair of read bitlines to said corresponding pair of common main read bitlines in response to an applied enable control signal.  
           [0034]    In another aspect of the invention, each said memory cell comprises a pre-determined number of read data transmission gates transmitting read data to the corresponding read bitline in response to a corresponding read word line control signal applied through the corresponding read word line, a pre-determined number of write data transmission gates transmitting write data of the corresponding write bitline in response to a corresponding write word line control signal applied through the corresponding write word line, a latch latching the write data transmitted from a pre-determined number of the write data transmission gates, and a pre-determined number of read data driving gates driving the stored data in the latch and outputting the stored data to the corresponding read data transmission gate.  
           [0035]    In another aspect of the invention, the applied enable control signal is generated by decoding pre-determined bits in a row address.  
           [0036]    In another aspect of the invention, each of the multiple repeaters in each sub-array according to claim 1 comprises a first inverter inverting a signal of the read bitline, a second inverter inverting the output signal of the first inverter in response to the applied enable control signal, a first PMOS transistor with a source applying a power voltage, a drain applying a signal of the read bitline, and a gate applying the output signal of the first inverter, a first NMOS transistor with a drain connected to the drain of the first PMOS transistor, and a gate applying the applied enable control signal, and a second NMOS transistor with a source applying a ground voltage, and a gate applying the output signal of the first inverter,  
           [0037]    wherein a source of the first NMOS transistor is connected to a drain of the second NMOS transistor.  
           [0038]    Also disclosed is a semiconductor memory device comprising a memory array comprising a plurality of sub-arrays, each said sub-array comprising a plurality of memory cells, said memory cells connected to a corresponding pair of read word lines, a corresponding pair of read bitlines, a corresponding pair of write word lines, and a corresponding pair of write bitlines, multiple repeaters in each sub-array, each of the multiple repeaters connected to both the corresponding pair of read bitlines and the corresponding pair of common main read bitlines for connecting commonly the corresponding pair of read bitlines in each sub-array, transmitting read data in the corresponding pair of read bitlines to the corresponding pair of common main read bitlines, in response to an applied enable control signal, and multiple write repeaters in each sub-array, each of the multiple write repeaters connected to both the corresponding pair of write bitlines and the corresponding pair of common main write bitlines for connecting commonly the corresponding pair of write bitlines in each sub-array, transmitting write data in the corresponding pair of write bitlines to the corresponding pair of common main write bitlines, in response to an applied enable control signal.  
           [0039]    In another aspect of the invention, each memory cell comprises a pre-determined number of read data transmission gates transmitting read data to the corresponding read bitline in response to a corresponding read word line control signal applied through the corresponding read word line, a pre-determined number of write data transmission gates transmitting write data of the corresponding write bitline in response to a corresponding write word line control signal applied through the corresponding write word line, a latch latching the write data transmitted from a pre-determined number of the write data transmission gates, and a pre-determined number of read data operation gates operating the stored data in the latch and outputting the stored data to the corresponding read data transmission gate.  
           [0040]    In another aspect of the invention, the applied enable control signal is generated by decoding pre-determined bits in a row address.  
           [0041]    In another aspect of the invention, each said repeater comprises a first inverter inverting a signal of the read bitline, a second inverter inverting the output signal of the first inverter in response to the applied enable control signal and transmitting the inverted output signal to the corresponding common main read bitline, a first PMOS transistor with a source applying a power voltage, a drain applying a signal of the read bitline, and a gate applying the output signal of the first inverter, a first NMOS transistor with a drain connected to the drain of the first PMOS transistor, and a gate applying the applied enable control signal, and a second NMOS transistor with a source applying a ground voltage, a drain connected to the source of the first NMOS transistor, and a gate applying the output signal of the first inverter.  
           [0042]    In another aspect of the invention, each said write repeater in each said sub-array comprises a third inverter inverting a signal of the common main write bitline, a fourth inverter inverting the output of the third inverter in response to the applied enable control signal, and transmitting the inverted output signal to the write bitline, a second PMOS transistor with a source applying a power voltage, a drain applying a signal of the common main write bitline, and a gate applying the output signal of the third inverter, a third NMOS transistor with a drain connected to the drain of the second PMOS transistor, and a gate applying the applied enable control signal, a fourth NMOS transistor with a source applying a ground voltage, and a gate applying the output signal of the third inverter, and wherein a source of the third NMOS transistor is connected to a drain of the fourth NMOS transistor.  
           [0043]    Disclosed is a data read method in a semiconductor memory device comprising a memory array comprising a plurality of sub-arrays, each said sub-array comprising a plurality of memory cells, said memory cells connected to all of a corresponding pair of read word lines, a corresponding pair of read bitlines, a corresponding pair of write word lines and a corresponding pair of write bitlines, the data read method , transmitting read data of the corresponding pair of read bitlines to a corresponding pair of common main read bitlines so as to commonly connect the corresponding pair of common main read bitlines to the corresponding pair of read bitlines in each sub-array, in response to an applied enable control signal selecting each sub-array.  
           [0044]    In another aspect of the invention, the data read method further comprises transmitting write data in the common main write bitlines so as to commonly connect the corresponding pair of common main write bitlines in each sub-array to the corresponding pair of write bitlines, in response to an applied enable control signal in a write operation.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0045]    For a 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:  
         [0046]    [0046]FIG. 1 is a block diagram illustrating an example of a conventional semiconductor memory device with both multiple data read ports and multiple data write ports.  
         [0047]    [0047]FIG. 2 is a circuit diagram illustrating a memory cell of a preferred embodiment of the invention.  
         [0048]    [0048]FIG. 3 is a block diagram illustrating a semiconductor memory device comprising multi data read ports and multi data write ports, according to a preferred embodiment of the invention.  
         [0049]    [0049]FIG. 4 is a circuit diagram illustrating a repeater in a preferred embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0050]    Reference will now be made in detail to preferred embodiments of the present invention, example of which is illustrated in the accompanying drawings.  
         [0051]    Referring to FIG. 3, there is shown a block diagram illustrating a semiconductor memory device comprising multiple data read ports and multiple data write ports, according to a preferred embodiment of the invention. As illustrated in FIG. 3, memory cell array  100  is substituted for memory cell array  10  in FIG. 1 and it is to be understood that peripheral devices shown in the drawing identified by numerals identical to those in FIG. 1 operate in the same manner as those described with respect to FIG. 1. The memory array  100  of FIG. 3 may utilize the prior art memory cells described in FIG. 2.  
         [0052]    Memory cell array  100  of a preferred embodiment of the invention is divided into four memory cell sub-arrays  100 - 1 ,  100 - 2 ,  100 - 3 , and  100 - 4 , and read bitlines rb 11 , rb 12 , rb 21 , rb 22 , . . . , rbk 1 , rbk 2  are divided into four parts, each in one of the four sub-arrays.  
         [0053]    Each of read bitlines rb 11 , rb 12 , rb 21 , rb 22 , . . . , rbk 1 , rbk 2 , divided into four parts, is connected to common main read bitlines rm 11 , rm 12 , rm 21 , rm 22 , . . . , rmk 1 , rmk 2  through repeaters  40 - 11 ,  40 - 12 ,  40 - 21 ,  40 - 22 , . . . ,  40 -k 1 ,  40 -k 2 . The common main read bitlines rm 11 , rm 12 , rm 21 , rm 22 , . . . , rmk 1 , rmk 2  are connected to the first and the second column read multiplexers  16 - 1  and  16 - 2 .  
         [0054]    Each of the corresponding repeaters  40 - 11 ,  40 - 21 , . . . ,  40 -k 1  in the four divided memory cell sub-arrays  100 - 1 ,  100 - 2 ,  100 - 3 ,  100 - 4  outputs read data in response to each of four corresponding repeater control signals rc 11 , rc 21 , rc 31 , rc 41  generated by decoding an upper two bits in the first row address. Each of the corresponding repeaters  40 - 12 ,  40 - 22 , . . . ,  40 -k 2  in the four divided memory cell sub-arrays  100 - 1 ,  100 - 2 ,  100 - 3 ,  100 - 4  outputs read data in response to each of four corresponding repeater control signals rc 12 , rc 22 , rc 32 , rc 42  generated by decoding an upper two bits in the second row address. Repeaters  40 - 11 ,  40 - 21 , . . . ,  40 -k 1  in the memory cell sub-array  100 - 1  output read data in response to the repeater control signal rc 11  when the upper two bits of the first row address are “00”. Repeaters  40 - 11 ,  40 - 21 , . . . ,  40 -k 1  in the memory cell sub-array  100 - 2  output read data in response to the repeater control signal rc 21  when the upper two bits of the first row address are “01”. Similarly, Repeaters  40 - 12 ,  40 - 22 , . . . ,  40 -k 2  in the memory cell sub-array  100 - 3  output read data in response to the repeater control signal rc 32  when the upper two bits of the second row address are “10”. Repeaters  40 - 12 ,  40 - 22 , . . . ,  40 -k 2  in the memory cell sub-array  100 - 4  output read data in response to the repeater control signal rc 42  when the upper two bits of the second row address are “11 ”.  
         [0055]    By dividing bitlines rb 11 , rb 12 , rb 21 , rb 22 , . . . , rbk 1 , rbk 2  into four parts, bitline load capacitances are reduced. Of course, the invention is not limited to a four-part division. The teachings of the invention may be generalized to any n-part divisions as desired.  
         [0056]    Each of divided read bitlines rb 11 , rb 12 , rb 21 , rb 22 , . . . , rbk 1 , rbk 2  is connected to each of corresponding common main read bitlines rm 11 , rm 12 , rm 21 , rm 22 , . . . , rmk 1 , rmk 2 . Line load capacitances in each of common main read bitlines rm 11 , rm 12 , rm 21 , rm 22 , . . . , rmk 1 , rmk 2  is less than those of read bitlines rb 11 , rb 12 , rb 21 , rb 22 , . . . , rbk 1 , rbk 2  in the conventional semiconductor memory device of FIG. 1, because each of common main read bitlines rm 11 , rm 12 , rm 21 , rm 22 , . . . , rmk 1 , rmk 2  connect to only four repeaters.  
         [0057]    Referring to FIG. 4 there is depicted a circuit diagram illustrating a repeater in a preferred embodiment of the invention. The repeater comprises PMOS transistor P 3 , NMOS transistors N 9  and N 10 , inverters  14  and  15 , and tri-state inverter  16 .  
         [0058]    The specific repeater here illustrated as an example is that labeled  40 - 21  in FIG. 3. The repeater is connected to both the read bitline rb 11  and the common main read bitline rm 11 . The inverter  14  inverts read data in the read bitline rb 11 . The source of PMOS transistor P 3  is connected to a power voltage VDD, the drain to the read bitline rb 11 , and the gate to the output signal of the inverter  14 . The source of NMOS transistor N 9  is connected to the drain of NMOS transistor N 10 , the drain of N 9  connects to the drain of PMOS transistor P 3 , the gate of N 9  to the repeater control signal rc 12 . The source of NMOS transistor N 10  is connected to a ground voltage VSS, the drain to the source of NMOS transistor N 9 , and the gate to the output signal of the inverter  14 . The inverter  15  inverts the repeater control signal rc 12 . The tri-state inverter  16  outputs the signal of the inverter  14  to the common main read bitline rm 11  in response to both the output signal of the inverter  15  and the repeater control signal rc 12 .  
         [0059]    The operation of the repeater of FIG. 4 is as follows:  
         [0060]    As an example, assume a transmitted signal to the read bitline rb 11  is a “low” logic level so that inverter  14  is now inverting a logical “low” so as to generate a logical “high”. Further assume that the repeater control signal rc 12  is “low”. The tri-state inverter  16  turns on in response to the “low” repeater control signal rc 12  and inverts the “high” output signal of the inverter  14  to a logical “low” that is then asserted on the common main read bitline rm 11 . Hence, the “low” signal on line rb 11  has been repeated to line rm 11 .  
         [0061]    Likewise, so long as the repeater control rc 12  is “low”, a “high” signal on read bitline rb 11  will be repeated to the common main read bitline rm 11 . In addition, PMOS transistor P 3  turns on in response to the “low” output signal of the inverter  14 , and thereby amplifies the “high” input applied to the inverter  14 . In other words, PMOS transistor P 3  is turned on to enlarge the signal of “high” logic levels in the read bitline rb 11  because data transmission performance of “high” logic levels in NMOS transistors is poor.  
         [0062]    The repeater in the semiconductor memory device of the invention in FIG. 4 buffers and transmits read data between the read bitline and the common main read bitline. In addition, the repeater of FIG. 4 assists “high” logic level signals inputted from the bitline thereby improving operation speeds in transmitting “high” signals.  
         [0063]    A preferred embodiment of the invention in FIG. 3 divides the read bitline in the memory cell array into four parts. However, at least more than two divided read bitlines in the memory cell array is enough to get the same effects in the above statements. In other words, the read bitline can be divided appropriately according to the increase in the number of memory cells connected to the read bitline. Too many numbers of repeaters in memory cell array may occupy too large a layout area. Therefore, it is preferable that the read bitline is divided appropriately by speed versus space.  
         [0064]    The above description of the invention divides the read bitline to improve the read operation speed. In another embodiment the write bitlines may also be divided to improve both read and write operation speeds.  
         [0065]    It is to be understood that all physical quantities disclosed herein, unless explicitly indicated otherwise, are not to be construed as exactly equal to the quantity disclosed, but rather about equal to the quantity disclosed. Further, the mere absence of a qualifier such as “about” or the like, is not to be construed as an explicit indication that any such disclosed physical quantity is an exact quantity, irrespective of whether such qualifiers are used with respect to any other physical quantities disclosed herein.  
         [0066]    While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration only, and such illustrations and embodiments as have been disclosed herein are not to be construed as limiting to the claims.