Dynamic semiconductor memory device

Abstract: A sense amplifier (3) is connected between memory cell arrays (l₁ and l₂), a re-writing register (5) is arranged in position adjacent to the sense amplifier (3), transfer gates (4, 6 and 9) are disposed between the sense amplifier (5) and the memory cell arrays (l₁ and l₂), transfer gates (7) are provided between bit lines (BL and /BL) of the memory cell arrays (l₁ and l₂) and global bit lines (GBL and /GBL), and a gate control circuit (10) for controlling the transfer gates is provided. When readout data is written into the register (5), the node of the sense amplifier (3) is electrically separated from the bit lines (BL and /BL) and global bit lines (GBL and /GBL).

Description: This invention relates to a dynamic semiconductor memory device (DRAM). A DRAM having a memory cell array which is constructed by forming a plurality of NAND memory cell units each of which is constructed by a plurality of series-connected memory cells and connecting a plurality of memory cell units to bit lines is known in the prior art. In this memory cell array system, the number of bit line contacts can be made small in comparison with a system in which memory cells are individually connected to bit lines and therefore the cell area can be reduced. With the above NAND cell array system, when data is read out from a memory cell of the memory cell unit which lies at a long distance from the bit line, data of memory cell or cells lying between the readout memory cell and the bit line must be destroyed. Therefore, it becomes necessary to use a register for temporarily holding the data of the memory cell unit and re-write the data (for example, refer to IEEE ISSCC DIGEST OF TECHNICAL PAPERS, VOL. 34, p106, TAM.2, 1991). As the layout method for the above temporary storing register, a method of commonly using a register for a plurality of memory cell arrays is provided. In this method, a global bit line is arranged to cross a plurality of memory cell arrays, nodes of a plurality of sense amplifiers are connected to the global bit lines via transfer gates and a register is connected to one end of the global bit line. However, in the above conventional system, it is necessary to charge and discharge the global bit line which has a larger capacitance than the bit line arranged in the memory cell array in order to re-write data which is temporarily stored in the register. Therefore, in the conventional DRAM, the power consumption in the data re-writing operation is large. In the above NAND cell array system, since the cell area is small, the open bit line system may be effectively used. Therefore, in the cell array system, a pseudo-folded bit line system which is a modification of the open bit line system is proposed. This system is a system in which a dummy cell array arranged at the end portion of the memory block is commonly used by memory cell arrays in the memory block. However, in this system, it is necessary to construct the dummy cell array by memory cell units each formed of a plurality of series-connected dummy cells in the same manner as in the memory cell array and therefore the area of the dummy cell array becomes large. In the conventional ordinary DRAM in which each memory cell is connected to a corresponding one of bit line contacts, the operation of writing data into a memory cell from the exterior of the chip is effected at the same time of effecting the active restoring operation in which data is read out from a memory cell to a bit line pair, a potential difference is amplified to Vcc and Vss by a sense amplifier, data is transferred to a DQ line, and then data is re-written into the memory cell. In the above system, the readout mode and write-in mode of the DRAM are not separated from each other and it is not necessary to provide a circuit for setting the mode. However, in this method, when data is read out from the memory cell to the bit line pair and data set in an inverted relation with respect to data obtained by amplifying a potential difference between Vcc and Vss by use of the sense amplifier is written from the exterior, the operation is active, and since the potentials Vcc and Vss on the two nodes of the sense amplifier for amplifying data from the memory cell to the potential difference between Vcc and Vss must be inverted to Vss and Vcc, respectively, the power consumption becomes large. In addition, in the DRAM in which a memory cell unit formed of series-connected memory cells is connected to a bit line, the memory cells are serially so that data of the memory cell cannot be read out at random and at a high speed. As described above, in the conventional DRAM in which a NAND memory cell unit is constructed by serially connecting a plurality of memory cells, it is necessary to charge and discharge the global bit line in order to re-write data and the power consumption becomes large. In the case of using the pseudo-folded bit line system, the cell area of the conventional DRAM is increased by an amount corresponding to the dummy cell array. Further, the memory cells are serially connected in the conventional DRAM, data of the memory cell cannot be read out at random and at a high speed. In an ordinary DRAM in which each memory cell is connected to a corresponding one of bit line contacts, when data is written into the memory cell and data set in an inverted relation with respect to data obtained by amplifying a potential difference to Vcc and Vss by use of the sense amplifier is written from the exterior, the operation is active, and since the potentials Vcc and Vss on the two nodes of the sense amplifier for amplifying data from the memory cell to the potential difference between Vcc and Vss must be inverted to Vss and Vcc, respectively, the power consumption becomes large. An object of this invention is to provide a DRAM which has memory cell units each constructed by serially connecting a plurality of memory cells and in which the power consumption is lowered and an erroneous readout operation can be prevented. Another object of this invention is to provide a DRAM in which the power consumption at the time of writing data can be suppressed by controlling the operation of a first sense amplifier when data is written from the exterior and then writing the data into a memory cell. This invention provides a dynamic semiconductor memory device comprising: a plurality of memory cell arrays (1 1 , 1 2 ) each constructed by a plurality of memory cell units which are each formed of a plurality of series-connected dynamic memory cells (MC), each memory cell array having a first bit line (BL, BL ) connected thereto; a first transfer gate connected to each said first bit line (BL, BL ); at least one first sense amplifier arranged between adjacent memory cell arrays (1 1 , 1 2 ), the sense amplifier having a first and second data nodes (N 1 , N 2 ), each data node being selectively connected via a first transfer gate to a different one of said first bit lines; at least one register arranged between said sense amplifier and said memory cell arrays and connected to at least one of said data nodes directly or via a second transfer gate, for temporarily storing memory cell data read out from a memory cell unit; and gate control means for controlling each said first transfer gates to selectively and electrically separate the first and second data nodes of said sense amplifier from each said first bit line in a case where data read out to one of said first bit lines is stored into said register from said sense amplifier. According to this invention, when data to be re-written is stored into the register for temporarily storing memory cell data, the sense amplifier can be operated with the first bit line electrically separated therefrom by controlling the transfer gate provided between the register and the first bit line by means of the gate control means. That is, the operation of storing data into the register can be effected without charging or discharging the first bit line so that the power consumption of a NAND type DRAM can be reduced, occurrence of noise which may be caused on the first bit line in the cell array when the sense amplifying operation is effected can be prevented and the readout operation can be stably effected. The DRAM according to an embodiment of this invention is characterized by further comprising a second bit line pair arranged to extend across said plurality of memory cell arrays and selectively connected to the second data node of said first sense amplifier; a switch connected to said second bit line pair, for controlling the operation of data transfer with respect to the exterior; a buffer for writing exterior data to said second bit line pair, a second sense amplifier for amplifying data read out from said memory cell; and control means for controlling said first sense amplifier, said switch and one of said buffer and said second sense amplifier to write data from said second bit line to said first bit line by use of said buffer and switch before said first sense amplifier is operated when exterior data is written via said second bit line. According to the above embodiment of this invention, data from the exterior of the chip is amplified by the buffer of the second sense amplifier and transferred to the first bit line via the second bit line before the first sense amplifier is operated in a case where the data from the exterior is written into the memory cell via the second bit line. Therefore, the power consumption caused in a case where the potentials of the input/output nodes of the first sense amplifier which are set to Vcc and Vss must be inverted in the prior art technique can be reduced. As described above, according to this invention, the temporarily storing registers are arranged adjacent to the sense amplifier disposed between the NAND memory cell arrays, the sense amplifier is operated with the bit line and global bit line electrically separated therefrom by controlling the transfer gate when memory cell data is stored into the register so that data can be stored into the register without charging and discharging the bit line, thereby making it possible to reduce the power consumption of the DRAM and suppress noise occurring at the readout time. Further, the power consumption can be reduced by transferring data from the global bit line pair to the bit line pair without operating the first sense amplifier by use of the second sense amplifier or write-in buffer when data is written into the memory cell from the I/O register cell. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figs. 1 and 2 are diagrams showing the construction of a first embodiment of a DRAM according to this invention, that is, the construction of a DRAM of an embodiment in which a register is provided on one side of a sense amplifier; Figs. 3A and 3B are diagrams respectively showing the constructions of a NAND memory cell unit and a register in the first embodiment; Figs. 4 and 5 are timing diagrams for illustrating the data readout operation of the first embodiment; Fig. 6 is a diagram showing the construction of a data transfer system control circuit in the first embodiment; Fig. 7 is a diagram showing the construction of an I/O register cell in the first embodiment; Figs. 8 to 12 are diagrams showing the concrete constructions of portions of the data transfer system control circuit shown in Fig. 6; Figs. 13A and 13B are diagrams respectively showing the concrete constructions of clocked inverters N 11 and N 12 ; Fig. 14 is a diagram showing the operation waveforms obtained at respective nodes when data is stored on the bit line pair from the I/O register; Fig. 15 is a diagram showing another example of the construction of the data transfer system control circuit of Fig. 6; Fig. 16 is a diagram showing another example of the construction of the I/O register cell of Fig. 7; Fig. 17 is a diagram showing another example of the construction of Fig. 8; Fig. 18 is a diagram showing another example of the construction of Fig. 12; Fig. 19 is a diagram showing the operation waveforms obtained at respective nodes in the construction of Figs. 15 and 16; Fig. 20 is a diagram showing a first modification of Fig. 1; Fig. 21 is a diagram showing a second modification of Fig. 1; Figs. 22 and 23 are diagrams showing the construction of a second embodiment of a DRAM according to this invention, that is, the construction of a DRAM of an embodiment in which registers are provided on both sides of a sense amplifier; Figs. 24 and 25 are timing diagrams for illustrating the data readout operation of the second embodiment; Figs. 26 and 27 are diagrams showing the construction of a DRAM of a first modification of the second embodiment in which the registers are provided on both sides of the sense amplifier; Figs. 28 and 29 are timing diagrams for illustrating the data readout operation of the first modification of the second embodiment; Figs. 30A and 30B are diagrams respectively showing examples of the construction of the memory cell of the register in the first modification of the second embodiment; Figs. 31 and 32 are diagrams showing the construction of a DRAM of a second modification of the second embodiment in which the registers are provided on both sides of the sense amplifier; Figs. 33 and 34 are timing diagrams for illustrating the data readout operation of the second modification of the second embodiment; Figs. 35 and 36 are diagrams showing the construction of a DRAM of a third modification of the second embodiment in which the registers are provided on both sides of the sense amplifier; Figs. 37 and 38 are timing diagrams for illustrating the data readout operation of the third modification of the second embodiment; Figs. 39 and 40 are diagrams showing the construction of a DRAM of a fourth modification of the second embodiment in which the registers are provided on both sides of the sense amplifier; Figs. 41 and 42 are diagrams showing the construction of a DRAM of a fifth modification of the second embodiment in which the registers are provided on both sides of the sense amplifier; Figs. 45 and 46 are circuit diagrams of a circuit for generating a basic signal used for controlling signals in Figs. 41 and 42; Fig. 47 is a timing diagram for illustrating the readout operation in the circuit of Figs. 45 and 46; Fig. 48 is a timing diagram for illustrating the re-writing operation in the circuit of Figs. 45 and 46; Fig. 49 is a diagram for illustrating the process of determining the readout order of signals in Figs. 41 and 42; Fig. 50 is a diagram for illustrating the process of determining the write-in order of signals in Figs. 41 and 42; There will now be described an embodiment of this invention with reference to the accompanying drawings. Figs. 1 and 2 are diagrams showing the construction of a first embodiment of a DRAM according to this invention, that is, the construction of a DRAM of an embodiment in which a register is provided on one side of a sense amplifier. This embodiment shows an example in which one memory cell unit is constructed by serially connecting four memory cells MC. The concrete construction of the memory cell is shown in Fig. 3A. As shown in Figs. 1 and 2, memory cell arrays 1 1 and 1 2 each having a plurality of memory cell units are arranged on both sides of a sense amplifier 3. Dummy cell arrays 2 1 and 2 2 are respectively connected to one-side end portions of the memory cell arrays 1 1 and 1 2 . The dummy cell array may be same construction as the memory cell unit which is constructed by serially connecting four memory cells. The memory cell MC and dummy cell DC are each formed with the one-transistor/one-capacitor structure which is used in an ordinary DRAM. The sense amplifier 3 includes a CMOS flip-flop which is constructed by nMOS transistors Q 51 and Q 52 and pMOS transistors Q 53 and Q 53 . An equalizer circuit 8 is provided adjacent to the sense amplifier 3. The equalizer circuit 8 includes precharge nMOS transistors Q 41 and Q 42 and an equalizing pMOS transistor Q 43 . A re-writing register 5 is arranged between the memory cell array 1 1 which is one of the two memory cell arrays and the sense amplifier 3 and equalizer circuit 8. In this embodiment, as shown in Fig. 3B, the register 3 is formed with the same construction as that of the memory cell MC used in the memory cell array. Further, in the register 5, four memory cells which are selected by register word lines RWL 0 to RWL 3 for respective data nodes RBL 0 to RBL 3 are arranged in positions corresponding to four memory cells MC selected by word lines WL 0 to WL 3 . Four bit lines BL 0 to BL 3 of the memory cell array l 1 which is one of the two memory cell arrays are respectively connected to the data nodes RBL 0 to RBL 3 of the register 5 via four nMOS transistors Q 11 to Q 14 of a transfer gate 4. The data nodes RBL 0 to RBL 3 of the register 5 are connected to a common connection node via respective nMOS transistors Q 21 to Q 24 of a transfer gate 6 and the common connection node is connected to a data node N1 which is one of the two data nodes of the sense amplifier 3. Four bit lines /BL 0 to /BL 3 of the other memory cell array 12 are connected to a common connection node via respective nMOS transistors Q 61 to Q 64 of a transfer gate 9 and the common connection node is connected to the other data node N 2 of the sense amplifier 3. The data nodes N 1 and N 2 of the sense amplifier 3 are respectively connected to global bit lines GBL and /GBL via nMOS transistors Q 31 and Q 32 of a transfer gate 7. The global bit lines GBL and /GBL are arranged to extend across the memory cell arrays 1 1 and 1 2 and are connected to data input/output lines (not shown). The transfer gate 7 for the global bit lines is shown in Figs. 1 and 2 for easy understanding of the connection relation between circuit portions respectively shown in Figs. 1 and 2 which are connected to each other in practice. A read/write gate control circuit 10 serves to control the transfer gates 4, 6, 7 and 9 in response to a clock. The gate control circuit 10 basically controls the transfer gates 4 and 6 so that only data of a selected bit line among data items read out from the memory cells to bit lines can be transferred to the data nodes of the sense amplifier 3 and re-written into a corresponding data node of the register 5 with the bit lines electrically separated therefrom. Figs. 4 and 5 show concrete waveforms for illustrating the data re-write operation for re-writing data read out by the readout operation of the first embodiment into the re-writing register 5. In this example, the explanation is made with much attention paid to the first bit of the memory cell unit to be selected by the word line WL 0 . Before data readout, transfer gate control signal lines  t0 to  t3 and  tR0 to  tR3 are all set to the "H" level and an equalization control signal line V BLEQ is set to the "H" level, and as a result, the bit lines, the node of the register 5 and the nodes of the sense amplifier 3 are precharged to (1/2)Vcc, for example, by means of the equalizing circuit 8. After this, the control signal lines  tR1 ,  tR2 ,  tR3 ,  tR5 ,  tR6 and  tR7 are set to the "L" level, and only the bit lines BL 0 and /BL 0 are respectively connected to the nodes N 1 and N 2 of the sense amplifier 3. In this condition, the word line is selectively driven. In this case, the potential of the word line WL 0 on the side of the memory cell array 11 rises and data items of memory cells arranged along the word line WL 0 are read out to the bit lines BL 0 to BL 3 . At this time, the potential of the dummy word line DWL1 of the dummy cell array 2 1 falls. This is because coupling noises caused on the bit lines by the fall of the potential of the word line WL 0 are canceled. Since the dummy cell line DWL 2 of the dummy cell array 22 on the side of the other memory cell array 1 2 is kept at the "H" level, data of the dummy cell array 2 2 is read out to the bit lines /BL 0 to /BL 3 . Only the data items of the bit lines BL 0 and /BL 0 among the data items of the bit lines BL 0 to BL 3 and /BL 0 to /BL 3 are transferred to the nodes N 1 and N 2 of the sense amplifier 3. After this, the control signal lines  tR0 ,  t4 and  t0 are sequentially set to the "L" level to electrically separate the bit lines which have been connected to the sense amplifier 3 and electrically separate the register 5 from the bit lines and sense amplifier 3. In this condition, the amplifying operation of the sense amplifier 3 is effected. After this, the control signal line  tR0 is set to the "H" level again to connect the node N 1 of the sense amplifier 3 to the node RBL 0 of the register 5 so as to permit data read out from the bit line BL 0 to be written into a selected memory cell of the register 5. At this time, the control signal line RWL 0 among the control signal lines RWL 0 to RWL 3 is set at the "H" level and data is re-written into the memory cell selected by the control signal line. The same operation is repeatedly effected to permit data items selected by the word line WL 0 and read out to the bit lines BL 0 , BL 1 , BL 2 and BL 3 to be sequentially transferred to the sense amplifier 3 and re-written into the four memory cells of the register 4 which are controlled by the control signal line RWL 0 . Re-writing into the memory cell from the re-writing register 5 performs that the data are written into memory cell block 1 by opening the transfer gate 4, after the sense amplifier 3 is operated by opening transfer gate 6 arranged on the bit line and connected the memory cell to be re-written to amplify the data of the register cell 5. The transfer gate connected the memory cell to be re-written can be opened after operating the sense amplifier 3. Although not indicated by the above operation waveforms, if the word line WL 1 is selected, data items of the memory cells arranged along the word line WL 0 are first read out and re-written into the memory cells of the register arranged along the control signal line RWL 0 , and then data items of the memory cells arranged along the word line WL 1 are re-written into the memory cells of the register arranged along the control signal line RWL 1 . During the operation of reading out the data items from the memory cell array to the re-writing register, the global bit lines GBL and /GBL are electrically separated from the data nodes N 1 and N 2 of the sense amplifier 3, and while the sense amplifier 3 is operated to write data into the register 5 as described above, the bit lines BL and /BL are electrically separated from the data nodes N 1 and N 2 of the sense amplifier 3. Therefore, according to this embodiment, it is not necessary to charge and discharge the bit lines and global bit lines during the operation of writing data into the register and the power consumption can be reduced. Fig. 6 is a diagram showing the construction of the data transfer system circuit of the first embodiment, and the data transfer system circuit for latching data read out from the bit line into the I/O register and writing data from the I/O register to a bit line pair. Fig. 7 is a diagram showing the construction of the I/O register cell of the first embodiment and a diagram showing data transfer control circuit 58. Each of the data transfer system circuit and an I/O register cell is provided one for each global bit line pair and a preset number of sense amplifiers 3. The data transfer system includes a read gate 51 constructed by nMOS transistors Q 71 and Q 72 , a register sense amplifier 52 constructed by pMOS transistors Q 81 , Q 91 and Q 92 and nMOS transistors Q 93 , Q 94 and Q 82 , a global bit line equalizing circuit 53 constructed by nMOS transistors Q 10,1 , Q 10,2 , and Q 10,3 , a write-in buffer 54 constructed by clocked inverters N 11 and N 12 , and an I/O data register  t gate circuit 55 constructed by nMOS transistors Q 11,1 and Q 11,2 . An I/O register cell includes a latch circuit 56 constructed by inverters N 22 and N 23 . A transfer gate constructed by nMOS transistors Q 12,1 and Q 12,2 controls data to transfer to an I/O via a DQ line pair of the I/O register cell 56. A control circuit 58 serves to control the transfer gates 51 to 55 according to data transfer control circuit driving signals BCEND and VWRACP, and the concrete construction thereof is shown in Figs. 8 to 12. The data transfer system control circuit 58 generally serves to control the gate GNLEQ of the global bit line pair equalizing circuit 53 so as to release the paired global bit lines from the equalized state at the readout time, and when data of the memory cell is read out to the global bit line pair, it controls the read gate RGATE of the read gate control circuit 51 to turn off the transistors Q 71 and Q 72 , controls RSEP and RSEN of the register sense amplifier 52 to amplify the potential difference between the paired global bit lines, and controls PHITR of the I/O register  t gate circuit 55 to turn on the transistors Q 11,1 and Q 11,2 so as to cause data to be written into the I/O register cell 56. At this time, the operation of the write-in buffer 54 is kept interrupted by controlling WBUFE and BWBUFE. On the other hand, when data is written from the I/O register into the memory cell, data of the I/O register cell 56 is read out to GBL 1 and /GBL 1 by controlling PHITR of the I/O register  t gate circuit 55, and then the readout data is transferred to the succeeding stage by controlling WBUFE and BWBUFE of the write-in buffer 54 and written into the bit line pair via the global bit line pair (GBL and /GBL). At this time, the read gate circuit 51, register sense amplifier circuit 52 and global bit line equalizing circuit 53 are kept deactivated by controlling the respective gates. A difference between the above embodiment and the conventional DRAM in the operation of writing data from the I/O register cell 56 into the memory cell is that the sense amplifier 3 of Fig. 2 is not operated and the power consumption is reduced when inverted potentials of the potentials of the nodes N 1 and N 2 are written unlike the case wherein the sense amplifier 3 is operated. Figs. 13A and 13B show the clocked inverters of N 11 and N 12 used as the buffer circuit 54. Figs. 13A and 13B respectively correspond to the inverters N 11 and N 12 . Fig. 14 shows the operation waveforms obtained at respective nodes when data is stored on the bit line pair from the I/O register. More specifically, Fig. 14 shows the operation waveforms obtained when potentials Vcc and Vss are respectively held on nodes N 5 and N 6 of the I/O register cell 56 and the potentials are stored on the nodes N 1 and N 2 of the sense amplifier 3. First, WBUFE and BWBUFE are respectively set to the "H" and "L" potential levels so as to write data from the I/O register onto the global bit line pair. That is, the write mode is set. Secondly, it is assumed that the write-in operation effected at this time utilizes the active restore effected at the time of the readout operation. That is, N 1 and N 2 are equalized and set to (1/2)Vcc, and the potential of the register word line RWLn (n = 0, 1, 2, 3) rises to permit data of the register cell to be read out onto the bit line. If the active restore is the operation effected at the readout time, data on the bit line pair is amplified since the sense amplifier is operated, but since the operation of the sense amplifier 3 is interrupted in this case, the data is not amplified. Thirdly, the potential of the I/O register is transmitted to the global bit line pair by applying the potential "H" to PHITR. Further, data is transmitted to the bit line pair from the global bit line pair by setting  tGBL to the "H" level and is written into the nodes N 1 and N 2 . Fourthly, when  tn (n = 0, 1, 2, 3) of the transfer gate 4 is set to "H", data of N 1 and N 2 is written into the memory cell l 1 . At this time, potentials Vcc and Vss are not applied from the exterior to the nodes SAP and /SAN of the sense amplifier 3 and the sense amplifier 3 is not operated. Therefore, unlike the conventional DRAM, since the sense amplifier 3 is not operated and the potentials Vcc and Vss of the nodes are not changed to Vss and Vcc when data is written into the odes N 1 and N 2 , the power consumption can be reduced. Another example of the data transfer system and I/O register is explained. The basic construction of the DRAM is the same as that of the former embodiment, but this embodiment is different from the former embodiment in the following respects. In the former embodiment, the write-in buffer 54 is used when data is written from the I/O register into the memory cell, but in this embodiment, the register sense amplifier 52 is used to effect the write-in operation. For this purpose, the data transfer system and I/O register cell are constructed as shown in Figs. 15 and 16. In Figs. 15 and 16, this embodiment is different from the former embodiment in that the buffer 14 is omitted. Further, the data transfer system control circuit 58' controls the gates PHITR, RGATE, RSEN, RSEP and GBLEQ in addition to the control process described above. The construction of the data transfer system control circuit 58' is basically the same as that shown in Figs. 8 to 12, but a circuit for creating WBUFE and BWBUFE in the portion of Fig. 8 is omitted as shown in Fig. 17 and the portion of Fig. 12 is modified as shown in Fig. 18. In this embodiment, the operation of reading out data from the memory cell into the I/O register is effected in exactly the same manner as in the former embodiment. When data is written into the memory cell from the I/O register, PHITR is first set to the "H" potential so as to permit the potentials of the I/O register to be transmitted to GBL and /GBL. Secondly, RSEP and RSEN are respectively set to the "L" and "H" potentials so as to permit the potential difference between GBL and /GBL to be amplified. Thirdly,  tGBL is set to the "H" potential to permit data to be transmitted from the global bit line pair to the bit line pair and written into the nodes N 1 and N 2 . At this time, like the former embodiment, the sense amplifier 3 is not operated in this embodiment and the power consumption can be reduced in comparison with the conventional DRAM. Fig. 19 shows the operation waveforms obtained at respective nodes in the construction of Figs. 15 and 16. Unlike the construction of Figs. 6 and 7, in this embodiment, RSEP and RSEN are respectively set to the "L" and "H" potentials so as to permit data from the I/O register to be amplified by a register sense amplifier 52. The other portion is the same as the corresponding portion of the construction of Figs. 6 and 7. In this case, RGATE is applied with the "H" potential. Fig. 20 shows a first modification in which the construction of the register 5 in the embodiment of Fig. 1 is made by two series-connected memory cells instead of two parallel-connected memory cells. Fig. 21 shows a second modification in which the register 5 is constructed by four series-connected memory cells like the memory cell array. In the above embodiment, the re-writing register is provided only on one side of the sense amplifier, that is, on the side of the bit line BL, but it is possible to symmetrically arrange re-writing registers on the sides of both of the bit lines BL and /BL. With this arrangement, data having an inverted relation with respect to data written into the register on the bit line BL side is written into the register on the bit line /BL side. In this case, the potential of (1/2)Vcc can be created by equalizing the re-writing registers on the bit line BL side and on the bit line /BL side in the precharge/equalize operation of the re-writing registers. Figs. 22 and 23 are diagrams showing the construction of a second embodiment of a DRAM according to this invention, that is, the construction of a DRAM of an embodiment in which registers are provided on both sides of the sense amplifier. Portions corresponding to those of the first embodiment in Figs. 1 and 2 are denoted by the same reference numerals used in Figs. 1 and 2. In this embodiment, the number of bit lines of a re-writing register section is 2 and re-writing registers 5 1 and 5 2 are symmetrically arranged on both sides of the sense amplifier 3. In Fig. 23, a dummy cell array on the side of the memory cell array 1 2 is omitted. In the first embodiment, the register 5 is arranged only on one side of the sense amplifier 3 and data of each of the memory cell arrays 1 1 and 1 2 is written into the register 5. However, in this embodiment, data of the memory cell array 1 1 may be written into the register 5 1 and data of the memory cell array 1 2 be written into the register 5 2 . That is, data read out onto the bit lines BL 0 to BL 3 via the word line WL 0 of the memory cell array 1 1 is written into four memory cells arranged along the register word lines RWL 0 and RWL 1 of the register 5 1 . Data read out onto the bit lines BL 0 to BL 3 via the word line WL 1 is written into four memory cells arranged along the register word lines RWL 2 and RWL 3 of the register 5 1 . Likewise, the register word lines RWL 4 and RWL 5 and the register word lines RWL 6 and RWL 7 are selected according to the word lines WL 2 and WL 3 used for data readout. The relation between the memory cell array 1 2 and the register 5 2 is the same as that between the memory cell array 1 1 and the register 5 1 . As an another method, a cell data may be stored to both side of the registered with a manner of a complementary signals. That is, a datum is stored by using each one bit of both side of the registers. In this arrangement, since capacities of signal nodes N 1 and N 2 of a sense amplifier and the register word lines RBL 1 and /RBL 1 , stable operation can be attained. In the case of this embodiment, the transfer gate control operation by the gate control circuit 10 is basically the same as in the former embodiment. That is, the control operation of setting the control signal lines  t0 to  t7 ,  tR0 and  tR1 to the low potential level when memory cell data is read out to the bit line, raising the potentials of the transfer gate control signal lines (one of  t0 to  t3 and one of  t4 to  t7 ) of the bit line pair for readout and lowering the potentials of the transfer gate control signal lines of the bit line pair for readout before the sense amplifier 3 is operated and the control operation of raising the potential of the control signal line (one of  tR0 and  tR1 ) of the register for write-in after the sense amplifier 3 is operated and a potential difference between the paired bit lines BL and /BL becomes sufficiently large and lowering the same after data is written into the memory cell of the register are effected. Figs. 24 and 25 show an example of operation waveforms of the second embodiment. Also, in this embodiment, an example in which the first one-bit data of four memory cells series-connected in the same manner as in the first embodiment is read out is explained, but the other bit can be read out by changing the address. Figs. 26 and 27 are diagrams showing the construction of a DRAM of a first modification of the second embodiment in which the registers are provided on both sides of the sense amplifier. In this modification, the transfer gates arranged between the register 51 and 52 on one hand and the nodes N 1 and N 2 of the sense amplifier 3 on the other in Figs. 22 and 23 are removed. Memory cell data items selected by the word line WL 0 and read out to the bit lines BL 0 to BL 3 are sequentially re-written into memory cells in the register 51 by use of the register word lines RWL 15 , RWL 14 , RWL 13 and RWL 12 . The operation waveforms of this modification are shown in Figs. 28 and 29. The transfer gate control operation by he gate control circuit 10 is effected in basically the same manner as in the second embodiment, and when data is written into the register, the bit lines and global bit lines are electrically separated from the data nodes of the sense amplifier. Figs. 30A and 30B show examples of the construction of the memory cell of the register used in the first modification of the first embodiment. The memory cell of the register may be a charge storage type memory cell having the same construction as the memory cell in the memory cell array as shown in Fig. 30A or as a memory cell constructed by three transistors as shown in Fig. 30B. Further, an SRAM cell can be used as the memory cell of the register. When the SRAM cell is used as the memory cell of the register, a stable write-in operation can be attained if the write-in circuit is constructed to write data items which are set in the inverted relation from both of the bit lines BL and /BL into the nodes D and /D of the DRAM cell. Figs. 31 and 32 are diagrams showing the construction of a DRAM of a second modification of the second embodiment in which the registers are provided on both sides of the sense amplifier. In this modification, the capacity of the registers 5 1 and 5 2 is set to half of the capacity in the embodiment of Figs. 22 and 23. In the case of this modification, data items of the bit lines BL 0 and BL 1 among the data items read out to the bit lines BL 0 to BL 3 by means of the word line WL 0 are written into memory cells arranged along the register word line RWL 0 of the register 5 1 arranged on the same side and data items of the bit lines BL 3 and BL 4 are written into memory cells arranged along the register word line RWL 4 of the register 5 2 arranged on the opposite side. The waveforms obtained in this case are shown in Figs. 33 and 34. Also, in this modification, the basic transfer gate control operation effected by the gate control circuit 10 is the same as in the case shown in Figs. 22 and 23, and when data is written into the register 5, the bit lines and global bit lines are electrically separated from the sense amplifier nodes. With the construction in which the bit lines BL and /BL are connected to bit lines in the re-writing register having the same capacity as in this modification, the (1/2)Vcc precharge operation after data is written into the re-writing register can be easily attained by directly connecting the bit lines RBL 0 and RBL 1 in the register to the respective bit lines /RBL 0 and /RBL 1 . Figs. 35 and 36 are diagrams showing the construction of a DRAM of a third modification of the second embodiment in which the registers are provided on both sides of the sense amplifier and shows an embodiment in which the capacity of the registers 5 1 and 5 2 is set to half of the original capacity. In the case of this modification, data items of the bit lines BL 0 and BL 1 among the data items read out to the bit lines BL 0 to BL 3 by means of the word line WL 0 are written into memory cells arranged along the along the register word lines RWL 15 and RWL 14 of the register 5 2 arranged on the opposite side and data items of the bit lines BL 3 and BL 4 are written into memory cells arranged along the register word lines RWL 7 and RWL 8 of the register 5 1 arranged on the same side. The operation waveforms obtained at this time are shown in Figs. 37 and 38. Also, in this modification, the transfer gate control operation by the gate control circuit 10 is effected in the same manner as in the case shown in Figs. 22 and 23, and the bit lines and the global bit lines are electrically separated from the sense amplifier nodes at the time of writing data into the register 5. Figs. 39 and 40 are diagrams showing the construction of a DRAM of a fourth modification of the second embodiment in which the registers are provided on both sides of the sense amplifier. In the third modification shown in Figs. 35 and 36, the data nodes of the registers 5 1 and 5 2 are commonly connected to the respective nodes N 1 and N 2 of the sense amplifier 3, but in this modification, two data nodes of the register 5 1 are respectively connected to the two nodes N 1 and N 2 of the sense amplifier 3 and two data nodes of the register 5 2 are respectively connected to the two nodes N 1 and N 2 of the sense amplifier 3. Also, in this modification, the control operation of separately writing data items read out to the bit lines BL 0 to BL 3 by means of the word line WL 0 , for example, into the register 51 arranged on the same side and into the register 5 2 arranged on the opposite side. In this case, noises induced on the nodes N 1 and N 2 via the nodes of the register can be canceled. Figs. 41 and 42 are diagrams showing the construction of a DRAM of a fifth modification of the second embodiment in which the registers are provided on both sides of the sense amplifier. Figs. 45 and 46 are circuit diagrams of the read/write gate control circuit shown in Fig. 41. Figs. 47 and 48 are timing diagrams showing the readout and re-write timings. Fig. 47 shows basic timings of various signals in the readout operation and Fig. 48 shows basic timings of various signals in the re-writing operation. The timings are determined based on the basic clock CK for reading one bit. Further, the order of reading 16 bits may be determined by counting CK and decoding to-be-selected word lines (WLi),  tk and RWLi according to the counting state as shown in Fig. 49. Fig. 50 shows the writing order in the same manner as shown in Fig. 49. 16-bit data can be read out by use of a combination of timing signals of one cycle shown in Figs. 47 and 48 and the orders shown in Figs. 49 and 50. In the read/write gate control circuits 10 shown in Figs. 1, 20, 21, 22, 26, 31, 35 and 39, the control terminals thereof are slightly different from one another. This invention is not limited to the above embodiments and can be variously modified without departing from the technical scope thereof.

Claims: A dynamic semiconductor memory device comprising: a plurality of memory cell arrays (1 1 , 1 2 ) each constructed by a plurality of memory cell units which are each formed of a plurality of series-connected dynamic memory cells (MC), each memory cell array having a first bit line (BL, BL ) connected thereto; a first transfer gate (4, 9) connected to each said first bit line (BL, BL ); at least one first sense amplifier (3) arranged between adjacent memory cell arrays (1 1 , 1 2 ), the sense amplifier (3) having first and second data nodes (N 1 , N 2 ), each data node being selectively connected via a first transfer gate (4, 9) to one of said first bit lines; at least one register (5) arranged between said sense amplifier and said memory cell arrays and connected to at least one of said data nodes directly or via a second transfer gate (6), for temporarily storing memory cell data read out from a memory cell unit; and gate control means (10) for controlling each said first transfer gate (4, 9) to selectively and electrically separate the first and second data nodes (N 1 , N 2 ) of said sense amplifier (3) from each said first bit line in a case where data read out to one of said first bit lines is stored into said register (5) from said sense amplifier (3). A dynamic semiconductor memory device according to claim 1, characterized in that the or each said register (5) is constructed by memory cells same as a plurality of memory cells connected to said first bit line. A dynamic semiconductor memory device according to claim 1, characterized in that the or each said register (5) is constructed by memory cells same as memory cells connected in a serial form and connected to said first bit line. A dynamic semiconductor memory device according to claim 1, characterized by further comprising: a third transfer gate (7) connected to each of said data nodes of said sense amplifier; a second bit line pair (GBL, /GBL) connected to said third transfer gate; and a second register (60) for storing said memory cell data via said second bit line pair. A dynamic semiconductor memory device according to claim 4, characterized by further comprising a data transfer circuit (58, 58') connected between said second register and said second bit line. A dynamic semiconductor memory device according to claim 1, characterized by further comprising: a second bit line pair (GBL, /GBL) arranged to extend across said plurality of memory cell arrays and selectively connected to the second data node of said first sense amplifier; a switch (7) connected to said second bit line pair (GBL, GBL ), for controlling the operation of data transfer with respect to the exterior; a buffer (54) for writing exterior data to said second bit line pair; a second sense amplifier (52) for amplifying data read out from said memory cell; and control means (58) for controlling said first sense amplifier, said switch and one of said buffer and said second sense amplifier to write data from said second bit line to said first bit line by use of said buffer and switch before said first sense amplifier is operated when exterior data is written via said second bit line. A dynamic semiconductor memory device according to claim 1, characterized by further comprising: a second bit line pair (GBL, /GBL) arranged to extend across said plurality of memory cell arrays and selectively connected to the second data node of said first sense amplifier; a switch (7) connected to said second bit line, for controlling the operation of data transfer with respect to the exterior of this device; a second sense amplifier (52) for amplifying exterior data and writing the data into said second bit line; and control means (58) for controlling said first sense amplifier, said switch and said second sense amplifier to write data from said second bit line to said first bit line by use of said amplifier means and switch before said first sense amplifier is operated when exterior data is written via said second bit line.

Inventors: HASEGAWA TAKEHIRO, MASUOKA FUJIO, OGIWARA RYU, OOWAKI YUKIHITO, SHIRATAKE SHINICHIROU, HASEGAWA, TAKEHIRO, MASUOKA, FUJIO, OGIWARA, RYU, OOWAKI, YUKIHITO, SHIRATAKE, SHINICHIROU, Hasegawa, Takehiro, c/o Int. Property Division, Masuoka, Fujio, c/o Int. Property Division, Ogiwara, Ryu, c/o Int. Property Division, Oowaki, Yukihito, c/o Int. Property Division, Shiratake, Shinichirou, c/o Int. Property Division
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1992
Main classification: G11C11
IPC codes: G11C11, G11C7