JP2000340771A - Semiconductor memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize area saving of a semiconductor memory device. SOLUTION: NMOSFETs 49 and 50, which are used to connect a pair of complementary bit line 15 extending from a subarray 32 and a sense amplifier 24a, are arranged on the opposite side of a sub array 32, which is not from the input side of the sense amplifier 25Pa. Accordingly, the NMOSFETs 49 and 50, having the threshold voltage same as that of the NMOSFET used on a logic circuit, can be used without the use of the material of low threshold voltage, the NMOSFETs 49 and 50 can be on/off operated surely in the narrow range of operation, and the scale and the function of a drive circuit can be suppressed low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor memory device such as a dynamic RAM which is suitable for being integrated on a semiconductor substrate together with a logic circuit.

[0002]

2. Description of the Related Art Conventionally, logic circuits such as microprocessors and application-specific integrated circuits (ASICs), and dynamic RAMs (DRAMs) and the like have been increasing in the degree of integration, respectively, and have high-performance large-scale integrated circuits (VLSI, U
LSI etc.). These integrated circuits are produced as individual chips, respectively, and in a system such as a personal computer, they are connected by external wiring on a system board.

However, in such a system, since the computing performance of the computer is limited by the parasitic capacitance and resistance of the external wiring, it is difficult to further improve the performance of the computer. Therefore, in recent years, the logic circuit, the DRAM, and the like are formed on the same semiconductor substrate to partially improve the performance. In recent years, in particular, the metal wiring of logic circuits has been multi-layered,
Attempts have been made to increase the number of metal wiring layers such as six layers or seven layers.

FIGS. 20 to 22 show an outline of a manufacturing process of a conventional semiconductor memory device in which a DRAM composed of two layers of metal wiring and a logic circuit using the DRAM are mounted on the same semiconductor substrate. 20 to 22 show partial cross-sectional structures of the DRAM region.
Each right figure shows a partial cross-sectional structure of the logic circuit region. First, as shown in FIG. 20, after forming a field oxide film 2 for element isolation on a Si (silicon) substrate 1, a gate oxide film 3, a gate electrode 4 of a transistor made of polycrystalline silicon, a word line (gate) A wiring 4a, a silicon oxide film 5 covering the upper portion, and diffusion layers 6 and 6a are formed. After an interlayer insulating film 217 is formed thereon by a CVD method, a part of the interlayer insulating film 217 is opened for forming a capacitor by a photoresist process and a dry etching process.

[0005] Next, in the DRAM region, the thin film deposition, the photoresist process, and the dry etching process are repeated, so that the storage electrode 201, the capacitance insulating film 202, the cell plate electrode of the memory cell capacitor shown in the left diagram of FIG. 203 are sequentially formed. Then, an interlayer insulating film 204 including the logic circuit region is formed thereon.

Next, in the DRAM region, as shown in the left diagram of FIG. 22, the above wirings and interlayer insulating films are alternately deposited and processed to form bit lines 206 made of a polycrystalline silicon film and a tungsten polycide film. A contact hole 205 connecting the bit line 206 and the diffusion layer 6a is formed.
After that, an interlayer insulating film 207 is formed so as to cover the upper portion including the logic circuit region.

In such a semiconductor memory device in which a DRAM region and a logic circuit region are mixedly mounted, as described above, the memory cell is composed of a memory cell transistor for address selection and a memory cell capacitor for data storage. Since the data storage operation is performed by accumulating the electric charge in the cell capacitor, it is necessary to increase the amount of the stored electric charge in order to read the data normally and at a high speed and to lengthen the data holding time.

[0008] The amount of charge stored in the memory cell capacitor of a DRAM is proportional to the voltage written to the memory cell.
The write voltage for “H” data is represented below. Write voltage = {α · Vcc− (Vtn + β)} · γ where α is a function of a time depending on a time constant due to a parasitic capacitance or resistance from a power supply voltage supply source to a memory cell (α ≦ 1) β: Increase in threshold value depending on back bias value γ: Coefficient (γ ≦
1) Vcc: power supply voltage Vtn: threshold value of the memory cell transistor Therefore, in such a DRAM, the write voltage can be increased by minimizing the second term (Vtn + β) of the equation, and therefore, Generally, the word line voltage is made higher than the power supply voltage Vcc, thereby canceling out the negative component of the second term.

However, when the DRAM region and the logic circuit region are mixedly mounted, as shown in FIGS. 20 to 22, the logic circuit region and the logic circuit region are formed in order to simplify the oxide film forming process.
It is desirable that the respective gate oxide films 3 in the RAM region are formed in the same step, and in this case, the thicknesses of the respective gate oxide films 3 in the logic circuit region and the DRAM region are the same. Since high speed is required in the logic circuit region, the thickness of the gate oxide film 3 is set to be relatively small, and the gate oxide film 3 in the DRAM region is inevitably thin. As a result, it is necessary to ensure the reliability of the gate oxide film 3 in the DRAM region, so that the word line cannot be boosted, and it is difficult to increase the write voltage, that is, to increase the amount of storage charge. Occurs.

As a method for solving such a problem, Japanese Unexamined Patent Publication No. Hei 10-134570 discloses a transistor having a lower threshold voltage (about 0.6 V) than usual as a transistor in a memory cell portion.
Is described. This makes it possible to reduce the second term of the above equation.

[0011]

In the conventional example, a so-called shared sense amplifier system is adopted.
The sense amplifier is further connected to a pair of bit lines disposed on both sides thereof via switching transistors disposed on both sides thereof. Therefore, a write voltage is applied to the memory cell capacitor via the switching transistor and the memory cell transistor. In such a circuit configuration, the voltage applied to the memory cell capacitor depends on the threshold values of both the switching transistor and the memory cell transistor. It drops by the value. Therefore, when a memory cell transistor having a low threshold is used, it is necessary to use a switching transistor having a similar low threshold.

However, when the threshold value of the switching transistor is lowered, the transistor is surely turned off.
It is necessary to use a negative voltage Vbb as a voltage for causing the circuit to drive, and as a result, a circuit for driving a wide operating range is required, which causes a problem that a layout area is increased.
There is a problem that the load of the Vbb generation circuit increases, the circuit scale increases, and the current consumption increases.

[0013] The present invention relates to a semiconductor memory device and an object thereof is to solve such a problem.

[0014]

In a semiconductor memory device according to the present invention, a first switching transistor for connecting a bit line extending from a memory sub-array to a sense amplifier is provided in the memory sub-array more than the input side of the sense amplifier. The gist is that it is arranged on the opposite side to the above.

This makes it possible to eliminate the first switching transistor from the data write path to the memory cell. Further, instead of using a low switching transistor as the first switching transistor, for example, a switching transistor having the same threshold as the transistor used in the logic circuit region can be used. The first switching transistor can be reliably turned on / off.

According to a second aspect of the present invention, there is provided a semiconductor memory device.
In the invention, the first sense amplifier is provided with a first P
A channel sense amplifier and an N-channel sense amplifier, wherein the first switching transistor is connected to the first
It is arranged between the P-channel sense amplifier and the N-channel sense amplifier to separate and connect them.

According to a third aspect of the present invention, in the semiconductor memory device, a first common bit line and a second common bit line complementary to the first common bit line are provided.
A common bit line, an N-channel sense amplifier connected between the first and second common bit lines, a first bit line, and a second bit line complementary to the first bit line. , A first bit line connected between the first and second bit lines.
A P-channel sense amplifier, a first switching transistor connected between the first common bit line and the first bit line, a second common bit line and the second bit line, , A third bit line, a fourth bit line complementary to the third bit line, and a third switching transistor connected between the third and fourth bit lines. A second P-channel sense amplifier, a third switching transistor connected between the first common bit line and the third bit line, a second switching transistor connected between the second common bit line and the fourth A fourth switching transistor connected between the bit line, a word line, a memory cell capacitor, and a fourth switching transistor connected between the first bit line and the memory cell capacitor and connected to the word line; Get A memory cell transistor having the door, further comprising a as its gist.

This makes it possible to eliminate the first switching transistor from the data write path to the memory cell. Further, instead of using a low switching transistor as the first switching transistor, for example, a switching transistor having the same threshold as the transistor used in the logic circuit region can be used. The first switching transistor can be reliably turned on / off.

According to a fourth aspect of the present invention, there is provided a semiconductor memory device.
4. The invention according to any one of the first to third aspects, wherein the memory cell transistor has a lower threshold value than a threshold value of the first switching transistor. This increases the storage capacity of the memory cell. According to a fifth aspect of the present invention, there is provided the semiconductor memory device according to any one of the first to fourth aspects, further comprising an N-channel driving transistor connected between a power supply node and the first P-channel sense amplifier. Is the gist. By doing so, the first P-channel sense amplifier can apply a voltage lower than the power supply voltage by the threshold voltage of the N-channel drive transistor to the first or second bit line.

According to a sixth aspect of the present invention, there is provided a semiconductor memory device according to the fifth aspect.
In the invention of the first aspect, the N-channel drive transistor includes:
The gist is to have a threshold value lower than the threshold value of the first switching transistor. As described above, even if the threshold value of the N-channel drive transistor is set low, both the voltage range for controlling the N-channel drive transistor and the voltage range for controlling the first switching transistor are set to, for example, a negative voltage. , It is not necessary to set a wide range using such a circuit, and a circuit for driving a wider operation range becomes unnecessary.

According to a seventh aspect of the present invention, there is provided a semiconductor memory device according to the fifth aspect.
In the invention of the first aspect, the N-channel drive transistor includes:
The gist of the present invention is to have a threshold almost the same as that of the memory cell transistor. An eighth aspect of the present invention provides the semiconductor memory device according to any one of the fifth to seventh aspects, further comprising a control circuit for selectively applying a power supply voltage and a ground voltage to the gate of the N-channel drive transistor. This is the gist.

According to a ninth aspect of the present invention, there is provided a semiconductor memory device according to the first aspect.
4. The invention according to any one of items 3 to 3, wherein each of the sense amplifiers includes two cross-connected sense transistors, and the sense transistor, the memory cell transistor, and the switching transistor have the same thickness. The gist is to have a gate insulating film.

A semiconductor memory device according to a tenth aspect is characterized in that the memory cell transistor has a grounded back gate. In a semiconductor memory device according to an eleventh aspect, in the invention according to the third aspect, a second P-channel sense amplifier is connected to a memory sub-array complementary to the memory sub-array, and the second P-channel sense amplifier is connected to the second sub-channel sense amplifier. The second with the N-channel sense amplifier
The gist of the present invention is to configure the sense amplifier. That is, the first sense amplifier and the second sense amplifier
Since a shared sense amplifier format is used for the complementary memory cell array, further area saving can be realized.

A semiconductor memory device according to a twelfth aspect of the present invention is the semiconductor memory device according to the sixth aspect of the present invention, wherein the semiconductor memory device is arranged between the second P-channel sense amplifier and the N-channel sense amplifier to separate and connect the two. The point is that a switching transistor is provided. Thus, the first switching transistor and the second switching transistor can be used by appropriately switching between the first sense amplifier and the second sense amplifier.

A semiconductor memory device according to a thirteenth aspect includes a power supply line, a ground line, and a plurality of memory cell arrays, wherein each of the memory cell arrays is adjacent to the subarray including a plurality of bit line pairs. A plurality of P-channel sense amplifiers respectively connected to the plurality of bit line pairs; and a plurality of P-channel sense amplifiers, each of which is provided with a power supply band. A plurality of power supply driving transistors connected between a line and a corresponding P-channel sense amplifier, a plurality of N-channel sense amplifiers respectively connected to the plurality of bit line pairs, and a plurality of N-channel sense amplifiers And a plurality of ground drive transistors each connected between the ground line and a corresponding N-channel sense amplifier. To include bets as its gist.
In this semiconductor memory device, the storage capacity can be easily increased simply by repeatedly designing a memory cell array having the same configuration.

According to a fourteenth aspect of the present invention, in the semiconductor memory device according to the thirteenth aspect, the plurality of memory cell arrays are arranged in a matrix, and the power supply driving transistors in the memory cell arrays arranged in each row of the matrix are provided with the power supply. The ground drive transistors in the memory cell arrays arranged in each row of the matrix are commonly connected to a ground line, and the power supply in the memory cell array arranged in each column of the matrix is commonly connected to the ground line. The drive transistor is commonly connected to the power supply line,
The gist is that the ground drive transistors in the memory cell array arranged in each column of the matrix are commonly connected to the ground line.

16. A semiconductor memory device according to claim 15, wherein: a semiconductor substrate; a dynamic random access memory formed on said semiconductor substrate; and a logic circuit formed on said semiconductor substrate for controlling said dynamic random access memory. The gist is that the memory cell capacitor in the dynamic random access memory has a capacitance insulating film having substantially the same thickness as a gate insulating film of a transistor constituting the logic circuit. Therefore, a capacitor insulating film of a memory cell capacitor and a gate insulating film of a transistor included in a logic circuit can be formed in the same step.

A semiconductor memory device according to a sixteenth aspect is the invention according to the fifteenth aspect, wherein the memory cell capacitor has a grounded cell plate electrode. Therefore, there is no need to provide a circuit for generating the cell plate voltage. In this case, in the second sense amplifier, the P-channel type field-effect transistor and the N-channel type in the second sense amplifier are interposed between the P-channel type field-effect transistor and the N-channel type field-effect transistor. It is desirable to dispose a second switching field-effect transistor for separating and connecting to the field-effect transistor.

In this way, the switching field-effect transistor and the second switching field-effect transistor can be used by appropriately switching between the sense amplifier and the second sense amplifier.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor memory device 31 embodying the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a layout of a semiconductor memory device 31 according to an embodiment of the present invention. Referring to FIG. 1, a semiconductor memory device 31 includes a global power supply line Vcc, a plurality of local power supply lines 36, a global ground line Vss, a plurality of local ground lines 37, and a plurality of memory cell arrays (MEMORY CEL).
L ARRAY) MA00-MAXy. The global power supply line Vcc and the global ground line Vss are made of an aluminum alloy, and are arranged at both ends of the semiconductor chip.
The local power line 36 is also made of an aluminum alloy,
It is orthogonal to and connected to global power supply line Vcc. The local ground line 37 is also made of an aluminum alloy, and is orthogonal to and connected to the global ground line Vss. Local power supply lines 36 and local ground lines 37 are arranged alternately. Memory cell arrays MA00-MAxy are arranged in a matrix. Each of the memory cell arrays MA00 to MAxy includes two subarrays (SUB ARRAY) 32 and a sense amplifier band (SENSE AMP BAND) 35. Sense amplifier band 35 is arranged at the center of the memory cell array, and sub-array 32 is arranged adjacent to both sides of sense amplifier band 35.

In the semiconductor memory device 31 shown in FIG.
Only two memory cell arrays 33 are shown, and therefore only four sub-arrays 32 are shown. Each subarray 3
2 has a storage capacity of, for example, 64K bits. A column decoder 3 is provided between the memory cell arrays 33 and 33.
4 are arranged. The sense amplifier band 35 is configured by a shared sense method, and a bit line pair is provided on the left and right with the sense amplifier band 35 as a center, and each subarray 32 is selectively connected to one of the left and right bit line pairs.
The sense amplifier band 35 includes a sense amplifier, a precharge circuit, and an input / output (I / O) line as described later.

The local power supply line 36 and the local ground line 37 are formed on the memory cell array 33 via an interlayer insulating film, and the global power supply line Vcc and the global ground are provided via contact holes formed at predetermined positions in the interlayer insulating film. Each is connected to a line Vss. In addition, since a plurality of local power supply lines 36 and local ground lines 37 need to be provided on a limited layout area, they have a width smaller than the width of global power supply line Vcc and global ground line Vss.

FIG. 3 is a control block diagram of the semiconductor memory device 31. Here, for convenience of explanation, 1
Only the memory cell arrays 33 are shown. The power supply voltage Vcc and the ground voltage Vss supplied from the local power supply line 36 and the local ground line 37 are respectively supplied to the column decoder 34, the main amplifier / I / O system (MAIN AMPLIFIER).
ER / I / O SYSTEM) 38, DRAM control circuit (CONTROL CI)
RCUIT) 39, Vbb generation circuit (GENERATION CIRCUIT)
40, a Vblp generation circuit (GENERATION CIRCUIT) 41 and a row decoder 42.

The Vbb generating circuit 40 comprises an oscillating circuit such as a ring oscillator and a charge pump circuit for generating a negative voltage by the oscillating pulse.
In response to ss, a known substrate back bias voltage Vbb is generated. The Vbb generation circuit 40 of the present embodiment receives the ground voltage Vss, and from this ground voltage Vss, the threshold voltage Vtn (about 0.4 to 0.5 V) of the memory cell transistor.
And a negative voltage Vbb that is only lower.

The Vblp generation circuit 41 generates a bit line precharge voltage Vblp. The Vblp generation circuit 41 is basically composed of an N-channel MOSFET source follower circuit, and supplies the power supply voltage Vcc to the MO
A voltage level shifted by the threshold voltage of the SFET is formed, and a voltage (half precharge voltage) obtained by dividing the voltage by half is generated.

In this embodiment, the ground voltage Vss is used as the cell plate voltage Vcp. However, by using the half precharge voltage, the withstand voltage characteristics of the capacitor insulating film of the capacitor can be further improved. it can. However, in this case, it is desirable to provide a circuit independent of the Vblp generation circuit 41 instead of using the half precharge voltage from the Vblp generation circuit 41.

The negative voltage V generated by the Vbb generation circuit 40
bb is supplied to the row decoder 42. The precharge voltage Vblp is supplied as a precharge signal to a precharge circuit described later, and the cell plate voltage Vcp is supplied to a memory cell capacitor. FIG. 4 is a main part plan view showing the memory cell structure of the sub-array 32. In the figure, a plurality of N-type semiconductor regions 11 (source / drain) are formed in a strip shape on one main surface of a P-type semiconductor substrate (silicon substrate) or a P-type well region. The semiconductor region 11 extends in the column direction and is arranged with both ends aligned. A groove 12 is formed on one main surface of the semiconductor substrate so as to overlap both ends of the plurality of semiconductor regions 11. The cell plate electrode 13 is made of polycrystalline silicon, and is formed on the semiconductor substrate via a capacitive insulating film (not shown) so as to be continuous with the groove 12 in the row direction. As a result, a trench memory cell capacitor for retaining charges between the semiconductor region 11 and the cell plate electrode 13 is formed in the trench 12.

The gate electrode 14 is connected to the cell plate electrode 13
Are disposed so as to intersect the semiconductor region 11 at a predetermined distance of two each. The gate electrode 14 is independent in two columns, and the cell plate electrode 13
And in the same layer and in the same step. Also, the gate electrode 1
4 is also formed in the same layer and in the same step as the capacitive insulating film below the cell plate electrode 13. Further, the gate electrode 14 and the gate insulating film thereunder are formed in the same manner as in the prior art by using the gate electrode and the gate insulating film of the MOS type FET in the logic circuit region (the gate electrode 4
And the gate oxide film 3) are formed in the same layer and in the same step, so that the cell plate electrode 13, the gate electrode 14, and the gate electrode of the FET in the logic circuit area are all formed in the same layer and in the same step. The lower insulating film is also formed in the same layer in the same step and has the same thickness. Therefore, the manufacturing process can be simplified, the number of layers to be multilayered is reduced, the cost can be reduced, and the manufacturing TAT (Turn Around Time) can be shortened.

Bit line 15 is made of, for example, aluminum, extends in the column direction along each semiconductor region 11, and is arranged on gate electrode 14 via an insulating film. This bit line 15 is electrically connected to the semiconductor region 11 through the contact hole 16 between the gate electrodes 14. The semiconductor region 11 to which the bit line 15 is connected is an island-shaped region separated from the trench capacitor by the gate electrode 14, and electrically independently forms a drain region. The intermediate wirings 17 and 18 overlap the gate electrode 14 between the bit lines 15 and extend in the column direction. One intermediate wiring 17 is formed to extend over the plate electrode 13, and the other intermediate wiring 18 is formed short enough to protrude slightly from the end of the gate electrode 14. The intermediate wirings 17 and 18 are formed in the same layer as the bit line 15 in the same step, and are electrically connected to the gate electrode 14 through contact holes 19 and 20, respectively.

Word line 21 is made of, for example, aluminum, extends in a direction crossing bit line 15, and is arranged on bit line 15 and intermediate interconnection 17 with an insulating film interposed therebetween. The word line 21 is arranged on the cell plate electrode 13 and the gate electrode 14, and the cell plate electrode 13
Is electrically connected to the intermediate wiring 17 through the contact hole 22, and the contact hole 2 is formed on the gate electrode 14.
3 and is electrically connected to the intermediate wiring 18. Therefore, each word line 21 is connected to the gate electrode 14 via the intermediate wirings 18 and 19, and applies a selection signal to each gate electrode 14.

The local power supply line 36 and the local ground line 37 are arranged on the word line 21 via an insulating film. Here, every other word line 21 is connected to the gate electrodes 14 arranged on the same row. That is, gate electrodes 14 arranged corresponding to 4n columns (n is an integer) and 4n + 1 columns are commonly connected to word lines 21 arranged in 4n + 1 and 4n + 2 rows, respectively.
Gate electrodes 14 arranged corresponding to columns 4n + 2 and 4n + 3 are commonly connected to word lines 21 arranged in rows 4n and 4n + 3, respectively. Thereby, each word line 2
No. 1 is a set of two memory cell transistors adjacent in the row direction and can be selected and activated every other set for each row.

In the above-described memory cell, the gate electrodes 14 are connected to the sense amplifier by combining columns separated from each other. As described above, in this semiconductor memory device, the DRAM circuit and the logic circuit for controlling the DRAM circuit are formed on the same silicon substrate. 5 to 7 are cross-sectional views showing a part of the manufacturing process of the semiconductor memory device. As shown in FIG. 5, a groove 12 is formed in the DRAM region of the silicon substrate 1, and an N-type well 1a and a P-type well 1b are formed. The storage electrode 201 is formed in the groove 12. As shown in FIG. 5, a field oxide film 2 for element isolation is formed in a region other than the element region.

Subsequently, as shown in FIG.
01, a capacitor insulating film 202 is formed, and at the same time,
The gate oxide film 3 of the memory cell transistor and the gate oxide film 3 of the transistor forming the logic circuit are formed. Subsequently, the cell plate electrode 13 is formed on the capacitor insulating film 202, and at the same time, the gate electrode 14 of the memory cell transistor and the gate electrode 14 of the transistor forming the logic circuit are formed.

Subsequently, as shown in FIG. 7, an interlayer insulating film 204 is formed over the entire DRAM region and logic circuit region. Subsequently, contact holes 16 and 218 are formed at predetermined positions of the interlayer insulating film 204, and the bit line 1 is formed.
5 and the wiring 219 are formed. Then, an interlayer insulating film 207 is formed over the entire DRAM region and the logic circuit region.

As described above, since the capacitance insulating film 202 of the memory cell capacitor and the gate oxide film 3 of the transistor constituting the logic circuit are formed in the same step, they have substantially the same thickness. The cell plate electrode 13 of the memory cell capacitor is connected to the ground line 37. Therefore, there is no need to provide a circuit such as the Vblp generation circuit 41 for supplying the cell plate voltage.

FIG. 8 is a circuit diagram of the DRAM.
In the figure, a plurality of memory cells each including a memory cell transistor MT and a memory cell capacitor MC are arranged in a matrix. The memory cell transistor MT
It is composed of a gate electrode 14 and a semiconductor region 11 divided by the gate electrode 14. The threshold value of each memory cell transistor MT is set to a value (about 0.4 to 0.5 V) lower than the threshold value (0.7 V) of the NMOSFET in the logic circuit area. Therefore,
The second term in the above equation becomes smaller, and the storage capacity can be increased.

In this embodiment, the ratio (CB) between the parasitic capacitance CB of the bit line and the capacitance CS of the memory cell capacitor is used.
/ CS) is maintained at 5 to 15 and the number of memory cell transistors MT connected to the pair of bit lines 15 and 15 complementary to each other is less than 256 in order to secure a data read voltage at the time of memory access. And The memory cell capacitor MC has a storage electrode 20 formed in the groove 12.
1 and the cell plate electrode 13 covering the storage electrode 201
And is connected to the source of each memory cell transistor MT by sharing the semiconductor region 11.

The bit line 15 is arranged so as to correspond to each column of the memory cell transistors MT, and the drain of the memory cell transistor MT is connected to each column. Two word lines 21 are arranged for each row of the memory cell transistors MT, and the gates of the memory cell transistors MT in two consecutive columns are connected to one of the two via the intermediate wirings 17 and 18, respectively. That is, the gates of the memory cell transistors MT arranged in the 4n column and the 4n + 1 column are connected to one of the word lines 21 arranged by two via the intermediate wiring 17, and the other is connected to the 4n + 2 Columns and 4n
The gates of the memory cell transistors MT arranged in the +3 column are connected via the intermediate wiring 18.

FIG. 9 shows a main part circuit diagram of the memory cell array 33. As described above, the memory cell array 33
Are two sub-arrays 32 (32a, 3a) complementary to each other.
2b) and a shared sense type sense amplifier band 35 provided therebetween. Subarray 32a
And 32b each include a plurality of bit line pairs. The sense amplifier band 35 includes a P-channel sense amplifier 25Pa provided for each pair of bit lines 15a1 and 15a2, a P-channel sense amplifier 25Pb provided for each pair of bit lines 15b1 and 15b2, and two pairs of bit lines 15a1. , 15
a2, 15b1, 15b2, an N-channel sense amplifier 25N, a precharge circuit 43, a local input / output line SubI / O, and a device for transferring data on a bit line to an input / output line pair SubI / O. It comprises a switch circuit 44.

One P-channel sense amplifier 25Pa or 25Pb and one N-channel sense amplifier 25N form one sense amplifier (SENSE AM) in FIG.
P) 25 is constituted. Each P channel sense amplifier 25
Pa is a P-channel MOSFET (hereinafter, referred to as a PMOS) in which a gate and a drain are cross-connected and in a latch form.
FETs) 45 and 46. Each P-channel sense amplifier 25Pb includes PMOSFETs 60 and 61 whose gates and drains are cross-connected to form a latch. Each N-channel sense amplifier 25N includes an N-channel type MOSFET (hereinafter, referred to as an NMOSFET) 4 in which a gate and a drain are cross-connected and latched.
7, 48.

A pair of bit lines 15a1 and 15a2 extending from one sub-array 32a are connected to a pair of common bit lines 151 and 152 via switching transistors (NMOSFETs) 49 and 50. A pair of bit lines 15b1, 15 extending from the other sub-array 32b
b2 is a switching transistor (NMOSFET)
A pair of common bit lines 151 and 152 via 58 and 59
Connected to. N-channel sense amplifier 25N is connected between common bit lines 151 and 152.

The gates of switching transistors 49 and 50 are commonly connected to sub-array selection signal line SBSR. In the present embodiment, the switching transistor 49,
Reference numeral 50 denotes an NM used for a logic circuit region without using a low-threshold one such as the memory cell transistor MT.
Since the same threshold value as that of the OSFET is used, S
The voltage amplitude range of the BSR can be set to Vss to Vcc.

The switching transistors 49 and 50 are
Sub-array 32 more than P-channel sense amplifier 25Pa
It is located on the opposite side to a. Each source of the PMOSFETs 45 and 46 is connected to the local power supply line 36 via a drive transistor (NMOSFET) 51. Four P-channel sense amplifiers 25 are connected to one local power supply line 36.
Pa are connected in common. Each gate of the drive transistor 51 is commonly connected to an activation signal line VSPL.

In this embodiment, the driving transistor 51
Are formed in the same step as the memory cell transistor MT, and are set to the same low threshold value. Therefore, a voltage level-shifted from power supply voltage Vcc by the threshold value of drive transistor 51 is applied to bit line 15 of sub-array 32a.
a1 and 15a2, the maximum potential difference between the gate electrode 14 connected to the word line 21 and the bit lines 15a1 and 15a2 can be reduced, and the withstand voltage of the gate insulating film of the memory cell transistor MT is ensured to improve reliability. And the voltage of the higher bit line is lower than the power supply voltage Vcc by the threshold value of the memory cell transistor, so that the restore voltage is reduced and power consumption can be reduced.

Further, by performing a voltage drop using drive transistor 51, the voltage amplitude range of activation signal line VSPL is not Vbb-Vcc but Vss-Vcc.
And the signal group to be negatively bias-controlled can be only the word line 21. As a result, a separate negative bias control circuit for the drive transistor 51 becomes unnecessary, and the power consumption can be reduced. Activation signal line VSPL is connected to DRAM control circuit 39 shown in FIG.
Supply voltage Vcc and ground voltage Vss are supplied alternately.

The sources of the NMOSFETs 47 and 48 are
The driving transistor (NMOSFET) 52 is connected to the local ground line 37. One local ground wire 3
7 is connected to one local power line 36
Four N-channel sense amplifiers 25N corresponding to the P-channel sense amplifiers 25Pa are commonly connected. Each gate of the drive transistor 52 is commonly connected to an activation signal line VSN. That is, the activation signal lines VSPL, V
Due to SN, the drive transistors 51 and 52 are turned on, and a voltage required for the operation of the sense amplifier 25 is supplied.

The precharge circuit 43 includes a PMOSFET
N provided between the NMOSFETs 45 and 46 and the NMOSFETs 47 and 48 for short-circuiting the pair of common bit lines 151 and 152.
MOSFET 53 and NMOSFET 5 for supplying precharge voltage Vblp to bit lines 151 and 152
4, 55. NMOSFET 53-55
Is a circuit activation signal SBS (in this embodiment, the power supply voltage V
cc) is supplied.

The switch circuit 44 includes an NMOSFET 5
The switching control is performed in accordance with the column selection signal GYS. In the present embodiment, four pairs of bit lines can be selected by one column selection signal GYS, but may be two pairs, eight pairs, or more. The data of each bit line pair is transmitted to the switch circuit 44.
Is connected to the input / output line SubI / O via

The gates of switching transistors 58 and 59 are commonly connected to sub-array selection signal line SBSL. The sources of the PMOSFETs 60 and 61 are commonly connected to a local power supply line 36 via a drive transistor (NMOSFET) 62. One local power line 36
, Four P-channel sense amplifiers 25Pb are commonly connected. Each gate of the drive transistor 62 is commonly connected to an activation signal line VSPR. Note that, similarly to the drive transistor 51, the drive transistor 62 is set to the same low threshold value in the same step as the memory cell transistor MT, so that the voltage amplitude range of the sub-array select signal line SBSL can be set to Vss to Vcc. .

FIG. 10 is a block diagram of a row decoder 42 for selecting a word line. Row decoder 42
Is a first row address detection circuit (FIRST ROW ADDRESS
DETECTION CIRCUIT) 63 and a second row address detection circuit (SECOND ROW ADDRESS DETECTION CIRCUIT) 64
And word line select circuit (WORD LINE SELECT CIRCUIT) 6
5 and a control circuit (CONTROL CIRCUIT) 66. The row decoder 42 finally selects one of the four word line addresses selected by the first row address detection circuit 63.

FIG. 11 shows the first row address detection circuit 6
3 and a specific circuit diagram of the word line selection circuit section 65. The first row address detection circuit 63 is a vertically stacked three-stage NMOSFET 67 having a row address as an input signal.
a to 67c. The word line selection circuit 65
It comprises a logic circuit 69 and a word line driver 70.

The logic circuit 69 has a signal supply line (/ R) for precharging when the row decoder is deactivated.
PMOSFET 71 whose gate is connected to DP)
, NMOSFETs 72 and 73 in which the gate and the drain are cross-connected to form a latch,
MOSFET 73 is connected to the drain, and the gate is connected to the first
Connected to the output terminal of the row address detection circuit 63 of FIG.
MOSFET 74 and a PMO connected between the drain of NMOSFET 72 and the gate of PMOSFET 74
It comprises an SFET 75 and a PMOSFET 76 whose gate is connected to the drain of the NMOSFET 73 and whose drain is connected to the gate of the PMOSFET 74. The power supply voltage Vcc is applied to the sources of the PMOSFETs 71, 74, and 76, and the PMOSFET 75
The ground voltage Vss is applied to the gate of
Negative voltage Vbb is applied to the sources of T72 and T73.

According to the configuration of the logic circuit 69, the PMOSFET 75 whose gate is connected to the ground voltage Vss is
It plays a role of source potential conversion and a role of actively cutting off the PMOSFET 74. As a result, a desired operation can be realized without using a logic element such as an inverter, the number of elements can be reduced, and the area can be reduced. This can contribute to an increase in operation speed.

Each word line 21 of the sub-array 32 has 2
NMOSFET 77, 78 connected to the stage, and NMOS
The output side of the FETs 77 and 78 is connected to the output side of a drive circuit 80 composed of an NMOSFET 79 whose drain is connected. Each drive circuit 80 constitutes a word line driver 70 as a set of four drive circuits. In the word line driver 70, the NMO of each drive circuit 80
The drain of the SFET 77 is commonly connected to the output terminal of the logic circuit 69, and the drain of the NMOSFET 78 is connected to four selection signal lines SX1 to SX from the control circuit 66, respectively.
X4.

NMOSFET 79 of each drive circuit 80
Is connected to the PMOSFET 71 of the logic circuit 69, and a negative voltage Vbb is applied to the source. Therefore, while the row decoder is inactive, the signal from the PMOSFET 71 of the logic circuit 69 causes the NMOSF
ET79 is turned on, and the potential of the word line 21 becomes Vb.
b.

NMOSFET 77 of each drive circuit 80
Is in a state where it can be always turned ON because its power supply voltage Vcc is always supplied to its gate. In response to a signal from the logic circuit 69, each NMO of the four drive circuits 80
The SFET 77 is turned ON all at once. Then this NMO
The NMOSFET 78 next to the SFET 77 can be turned on, and at this time, the four word lines 21 are selected.

Then, out of the four selection signal lines SX1 to SX4 from the control circuit 66, only the NMOSFET 78 connected to the activated one signal line performs signal transmission.
Finally, one word line 21 is selected. Here, the negative voltage Vbb is equal to the NMOSFETs 72, 7 of the logic circuit 69.
12 and the NMOSFET 79 of the drive circuit 80, respectively. In the present embodiment, as shown in FIG.
CURCUIT) 69 and the drive circuit (WORD LI)
The supply line LB to the NE driver 80 is formed by wiring of another system on the layout. That is, when the logic circuit 69 operates, the NMOSFETs 72 and 7 which discharge electric charges are provided.
3 is short-circuited with the source of the NMOSFET 79, which always keeps the word line 21 stably at the Vbb potential, on the layout.
3 becomes a noise source, and the word line 21
However, in this embodiment, the supply line LB is made independent so as to be less susceptible to noise.

In this embodiment, each drive circuit 8
The two-stage NMOSFETs 77 and 78 of 0 are set to the same low threshold value as the memory cell transistor MT. Therefore, the voltage applied to the gate of the NMOSFET 78 (Vcc-the threshold voltage of the NMOSFET 77) increases, and the time during which the NMOSFET 78 is turned on also decreases. As a result, the rising speed of the word line 21 increases.

FIG. 13 shows a redundant row address detecting circuit 81 and a word line selecting circuit 82 in a redundant row decoder.
3 shows a specific circuit diagram. The redundant row address detection circuit 81 includes a well-known fuse circuit 83 for programming a redundant address. Word line selection circuit 8
2 comprises a logic circuit 84 and a word line driver 85. The configuration of the word line driver 85 is the same as that of the word line driver 70.

The logic circuit 84 has a signal supply line (/ R) for precharging when the row decoder is deactivated.
PMOSFET 86 whose gate is connected to DP)
The source is connected to the output of the redundant address detection circuit 81, the drain is connected to the drain of the PMOSFET 86, the source signal is a PMOSFET 87 that becomes the first output to the word line driver 85, and the gate is A PMOSFET 88 connected to the drain of the PMOSFET 87, the drain signal of which is the second output to the word line driver unit 85;
Connected to the drain of SFET 88, the gate of which is connected to PM
NMOSFET connected to the drain of OSFET 87
89, an NMOSFET 90 whose gate is connected to the drain of the PMOSFET 88, and whose drain is connected to the drain of the PMOSFET 87;
PMOSF connected to the drain of MOSFET 88 and having its drain connected to the source of PMOSFET 87
ET91. And PMOSFET8
The power supply voltage Vcc is applied to each of the sources 6, 88, and 91, the ground voltage Vss is applied to the gate of the PMOSFET 87, and the negative voltage Vbb is applied to each of the sources of the NMOSFETs 89 and 90.

FIG. 14 shows the second row address detection circuit 6
4 and a specific circuit diagram of the control circuit 66. The second row address detection circuit 64 includes a PMOSFET 92
And a selection circuit 94a composed of a series of
To 94d in parallel, a power supply voltage Vcc is input to an input terminal of this parallel circuit, and an output terminal is an NMOSFET.
A configuration connected to (grounded to) the ground voltage Vss via the terminal 95 is adopted.

The PMOSFE of each of the selection circuits 94a to 94d
A signal supply line (/ RDP) is connected to the gate of T92. Also, the NMOS of each of the selection circuits 94a to 94d
The selection signal RA of the word line 21 is connected to the gate of the FET 93.
i is input, and the selection signal RAi causes the selection circuit 94
One of a to 94d is specified. Control circuit 66
Consists of four control circuit units 66a to 66d,
One selection signal line (SX1 to SX4) is derived from each of the control circuit units 66a to 66d, and this selection signal line is connected to the corresponding drive circuit 80 of the word line driver 70.

The input terminal of the control circuit unit 66a is connected to the output terminal of the selection circuit 94a. Similarly, the input terminal of the control circuit unit 66b is connected to the output terminal of the selection circuit 94b, and the input terminal of the control circuit unit 66c. Is connected to the output terminal of the selection circuit 94c, and the input terminal of the control circuit unit 66d is connected to the output terminal of the selection circuit 94d. The control circuit unit is specified according to the specified selection circuit. 21 will be specified.

Since the specific circuit configuration of each of the control circuit units 66a to 66d is the same, only the control circuit unit 66a will be described here. A signal XE for enabling word line selection (a signal defining a selection period of the word line 21) and its inverted signal are input to a NOR circuit 96, and an inverted signal of an output from the NOR circuit 96 and an output signal from a selection circuit 94a. Are input to the NOR circuit 97. The output terminal of the selection circuit 94a has a PMOSFET 9
8 are connected. Also, the selection circuit 94a
Is input to the gate of the PMOSFET 98 and also to the NAND circuit 99. N
The signal XE is input to the other input terminal of the AND circuit 99, and a signal obtained by inverting the signal from the NAND circuit 99 twice is supplied to the source of the PMOSFET 100 and the PMOSFE.
Input to the gate of T101.

The signal from the NOR circuit 97 is a PMOSF
The inverted signal is input to the gate of the ET 100 and the inverted signal is input to the source of the PMOSFET 102 and the PMOSFET.
Input to the gate of 103. The drain of the PMOSFET 102 is connected to the drain of the NMOSFET 104 of the NMOSFETs 104 and 105 whose gates and drains are cross-connected and in the form of a latch.
The drain of the FET 103 is connected to the drain of the NMOSFET 105.

The drain of the PMOSFET 100 has a gate-drain cross-connected N
NMOSFET 1 of MOSFETs 106 and 107
The drain of the PMOSFET 101 is connected to the drain of the NMOSFET 107. The drain of the NMOSFET 108 is connected to the selection signal line SX1 derived from the control circuit unit 66a.
The drain of T103 (the drain of NMOSFET 105) is connected. Further, the NMOSFET 108
Of the PMOSFET 101 (NM
The drain of the OSFET 107) is connected.

Then, the PMOSFETs 98, 101, 1
03, the source voltage Vcc is applied to each source and PM
Gate of OSFET 102 and NMOSFET 108
The ground voltage Vss is applied to the source of the NMOS FE.
A negative voltage Vbb is applied to each source of T104, 105, 106, 107. Next, the operation of the control circuit unit 66a configured as described above will be described with reference to the timing chart of FIG. Row address strobe signal / R
When signal / RDP attains H (logic high) level in response to activation of AS and furthermore, signal XE attains H level, the potentials of nodes J and K attain L (logic low) level. Therefore, the PMOSFET 101 is turned on and the NMOS
The FET 107 is turned off, thereby selecting the selection signal line SX.
1 is supplied with a power supply voltage Vcc. As a result, the voltage of the word line becomes the power supply voltage Vcc by the word line driver 85 shown in FIG.

Subsequently, when signal XE goes low, the potential at node J goes high and the potentials at nodes L and M both go low. When the potential of the node J becomes H level, the PMOSFET 101 is turned off, and the supply of the power supply voltage Vcc to the selection signal line SX1 is stopped. On the other hand, when the potential of the node L becomes L level, the PMOSFE
T103 is turned on. When the potential of the node M becomes L level, the NMOSFET 105 is turned off. for that reason,
The power supply voltage Vcc is applied to the gate of the NMOSFET 108, thereby turning on the NMOSFET 108.
The voltage of the selection signal line SX1 drops to the ground voltage Vss. Therefore, the voltage of the word line also drops to the ground voltage Vss. After a lapse of a predetermined time from the fall of signal XE, the potentials of nodes K, L, and M all go to L level. When the potential of the node K becomes L level, the NMOSFET 107 is turned on, and the voltage of the selection signal line SX1 drops to the negative voltage Vbb. When the potential of the node L becomes H level, PMO
The SFET 103 turns off. When the potential of the node M becomes H level, the NMOSFET 105 is turned on. Therefore, the gate voltage of the NMOSFET 108 becomes the negative voltage Vb
b, which turns off the NMOSFET 108.

With the circuit configuration described above, the control circuit unit 66a appropriately switches among three types of voltages, that is, the negative voltage Vbb, the power supply voltage Vcc, and the ground voltage Vss, and outputs the voltage on the selection signal line SX1. Here, there is a problem in control circuit unit 66a that through currents I1 and I2 flow at the time of rising and falling of signal XE. That is, when the signal XE goes high, the potential at the node J immediately goes low, but the potential at the node K goes low during the transmission time by the PMOSFET 100. Therefore, the PMOSFET 101 and the NMOSFET 107 are turned on at the same time, and a through current I1 flows. When the signal XE goes to L level, the potential of the node L immediately goes to L level, but the potential of the node M goes to L level with a delay of the transmission time by the PMOSFET 102. Therefore, the PMOSFET 103 and the NMOSFET 105 are turned on at the same time, and a through current I2 flows. When such through currents I1 and I2 flow, the negative voltage Vbb increases significantly. For this reason, the Vbb generation circuit 40 needs to restore the increased negative voltage Vbb to a predetermined voltage, which requires a large driving capability and increases power consumption.

In order to reduce such a through current,
As shown in FIG.
It is desirable to add SFETs 109 and 110, respectively. Here, the PMOSFET 101 and the NMO
A CMOS inverter is constituted by the SFET 109,
The PMOSFET 103 and the NMOSFET 110 form a CMOS inverter. Therefore, when the potential of the node J becomes L level and the PMOSFET 101 is turned on, the NMOSFET 109 is turned off. As a result, no through current flows even when the NMOSFET 107 is turned on. Similarly, when the potential of the node L becomes L level and the PMOSFET 103 is turned on, the NMOS
The FET 110 turns off. As a result, NMOSFET
No through current flows even when the switch 105 is turned on.

FIG. 17 is a diagram showing the arrangement of each component of the above-described semiconductor memory device on a well. As described above, the semiconductor memory device according to the present embodiment has P
It is formed in a type single crystal silicon substrate or a P-type well region (referred to as a P-type substrate region PWA). DRAM control circuit 3
9, main amplifier I / O system 38, Vbb generation circuit 40,
The logic circuit including the Vblp generation circuit 41, the address buffer, the clock circuit, and the like has an N-type well region N
WA and a P-type substrate region PWA are formed. Further, the cell block 32, the sense amplifier band 35, the row decoder 42
And a DRAM core composed of a column decoder 34 have N
The N-type well region NWB is formed in the N-type well region NWB deeper than the N-type well region NWA. In this manner, the N where the DRAM core is formed
By forming the N-type well region NWB deeper than the N-type well region NWA where the logic circuit is formed, the N-type well region NWB and the logic circuit region (LOGIC CIRCUIT RE
Noise from the GION) is in the DRAM core area (DRAM CORE RE
GION).

In the N-type well region NWB, the memory cell array 32 has NMOSFETs 47 to 50 and 52 to 59 having normal thresholds (the same as the thresholds of the NMOSFETs used in the logic circuit region). The memory cell transistor MT and the NMOSFETs 51 and 62 each having a lower threshold value are formed in different regions. The former is formed in the P-type well region PWA, and the latter is formed in the P-type well region PWB.

Similarly, the NMOSFETs 77 and 78 of the word line driver 80 having a low threshold value are also used for the row decoder.
And the other NMOSFETs are formed in different regions. The former is formed in the P-type well region PWB, and the latter is formed in the P-type well region PWA. In such a configuration, the operation of the semiconductor memory device according to the present embodiment is shown in FIG.
This will be described based on the timing chart shown in FIG. 14, J indicates the potential of the node J in FIG. 14, and N indicates the potential of the node N in FIG.

An address signal is fetched in synchronization with the fall of row address strobe signal / RAS. That is, the signal / RDP rises, and subsequently, the signal XG indicating the row address decision rises. Then, the potential of the signal line SBS of the precharge circuit falls, and further, the potential of the signal line SBSL falls. In this state, when the word line selectable signal XE rises, the potential of the node J falls, and the potential of the selection signal line SX1 (in this case, the control circuit unit 66a is selected) changes to the non-selection state. From the negative voltage Vbb to the power supply voltage Vcc.

As a result, the word line 21 is connected to the negative voltage Vbb.
Rises to the power supply voltage Vcc. The rising of the word line 21 causes a minute voltage change corresponding to the information charge of the selected memory cell on one of the pair of bit lines 15. Then, the rise of the potential of the signal line VSP activates the sense amplifier 25Pa, amplifies the potential change of the bit line, and outputs it to the input / output line subI / O.

When the selection of the word line 21 is completed, the signal X
E falls, and the potential of the word line 21 (selection signal line SX1) falls. At this time, the control circuit unit 66a
In response, a one-shot pulse is generated at node N in response to the fall of signal XE, and while this one-shot pulse is at a high level (power supply voltage Vcc), the potential of word line 21 is temporarily changed to ground voltage Vss. After that, the voltage of the word line 21 decreases to the negative voltage Vbb in response to the fall of the one-shot pulse. Thus, the read operation of the semiconductor memory device ends.

FIG. 19 shows the potential state of the memory cell in this embodiment. In the figure, the cell plate voltage Vcp and the voltage of the P-type well region PWB where the memory cell transistor MT is formed are both the ground voltage Vcp.
It is set to ss. FIG. 19A shows a write state of H level (“1”), and the word line 21 is shown.
Is set to 3.3 V, and the H level (2.3 V) of the bit line is written to the capacitor MC.

FIG. 19B shows a write state of L level (“0”). The gate voltage connected to word line 21 is set to 3.3 V, and the L level (0 V) of the bit line is set.
Is written to the memory cell capacitor MC. FIG. 19C
Indicates a data holding state, and the gate voltage connected to the word line 21 is set to the non-selection level of -0.5 V. At this time, the bit line is set to 0 V and 2.3 V of H in the write / read state. Level / L level, and a half precharge voltage of 1.2 V in a standby state. The holding voltage of the memory cell capacitor MC is 0 V or 2.3 V, and the source of the NMOSFET 79 for address selection is the negative voltage Vbb as described above. Therefore, even when the bit line or the holding voltage is 0 V, since the reverse bias voltage (-0.5 V) is applied, no leak current for erasing information charges flows.

The operation and effect of the semiconductor memory device of the present embodiment described above will be described below. (1) A memory cell transistor MT having a lower threshold than usual is used. Therefore, the second term of the above equation becomes smaller, and the storage capacity can be increased. (2) In the present embodiment, as shown in FIG. 19, the cell plate voltage Vcp is set to 0V. This is possible because the thicknesses of the capacitive insulating film of the memory cell capacitor MC and the gate insulating film of the transistor forming the logic circuit are all equal, as described above. In this way, even if a power supply voltage similar to that of the logic circuit region is applied to the memory cell capacitor MC, there is no problem because the withstand voltage of the capacitive insulating film is guaranteed based on the TDDB characteristic. Therefore,
The circuit operation can be stabilized using the ground voltage Vss, which is a stable voltage among various power supply voltages, as the cell plate voltage Vcp, and there is no need to use a special circuit for generating the cell plate voltage Vcp. Circuit area saving and cost reduction can be realized.

(3) In this embodiment, as shown in FIG. 19, the potential of the P-type well region PWB in which the memory cell transistor MT is formed is set to 0 V (ground voltage Vss). Therefore, the back gate effect in the memory cell transistor MT can be eliminated, and the second term of the above equation can be reduced, and the storage capacity can be increased.

(4) In the row decoder 42, the supply line LA to the logic circuit 69 and the supply line L to the drive circuit 80
Since B and B are formed by another type of wiring on the layout,
Noise is less likely to affect the word line 21 and highly accurate writing and reading operations can be performed. (5) The two-stage NMOSFET 77 of the drive circuit 80,
Since the threshold value of 78 is set to a low value equal to that of the memory cell transistor MT, the rising speed of the word line 21 is increased, and the writing / reading operation can be speeded up.

(6) Do not apply a high voltage between the bit line 15 and the word line 21 in order to maintain a good TDDB characteristic and perform a highly reliable design and reduce current consumption. When the word line 21 in the non-selected state is held at the negative voltage Vbb as in the present embodiment, it is desirable that the power supply voltage Vcc is not directly applied to the bit line as much as possible.

In this embodiment, the sense amplifier 25 Pa
(Consequently the bit line) to the power supply voltage Vc from the power supply line 36
Since the N-channel MOSFET 51 is used as a switching element for applying c, the power supply to the pair of bit lines 15 (the sense amplifier 25 Pa) is reduced compared to the case where a P-channel MOSFET is used as the switching element. A voltage whose level is shifted from the voltage Vcc by the threshold voltage Vtn of the NMOSFET 51 can be applied, so that the reliability of the circuit can be improved and the current consumption can be reduced.

Further, as compared with the case where a P-channel MOSFET is used as a switching element,
Parasitic capacitance generated in 5Pa (PMOSFETs 45 and 46) is reduced, and the operation of the sense amplifier 25Pa can be speeded up. (7) The switching transistors 49 and 50 for connecting the bit line pair to the common bit line pair are connected to the sense amplifier 2
The PMOSFETs 45 and 46 of 5 Pa are arranged on the side opposite to the sub-array 32a. Therefore, as the switching transistors 49 and 50, those having the same threshold value as the NMOSFET used in the logic circuit region can be used instead of using a low threshold value like the memory cell transistor MT. For example, when the switching transistors 49 and 50 have low threshold values, the switching transistors 49 and 50 can be reliably connected to O.
Although it is necessary to use the negative voltage Vbb as the voltage for the FF, in this embodiment, 0 V (ground voltage Vss) can be used as the voltage for surely turning off the switching transistors 49 and 50. As a result, the following effects can be obtained.

(A) Switching transistors 49 and 5
0 is the same as the negative voltage Vbb of the word line 21.
The power supply voltage is not the power supply voltage Vcc but the ground voltage Vss (0 V) to the power supply voltage Vcc. Therefore, the same circuit configuration and layout area as those of the word line driving circuit are not required, and the area can be reduced. (B) It is not necessary to increase the capability of the Vbb generation circuit 40, so that the layout area required for the Vbb generation circuit 40 can be reduced and the current consumption can be reduced.

(8) By arranging the power supply line 36 and the ground line 37 on the memory cell array 33 via an insulating film, the power supply line and the ground line and the memory cell array 33 are formed in different layers. Noise components such as a voltage drop of a power supply and a bound of a ground voltage generated when the sense amplifier is activated can be removed. As a result, α and γ in the above equation can be brought close to 1, and the storage capacity can be increased, and it is not necessary to take a special power supply strengthening measure.
Circuit size can be reduced.

(9) When the unselected word line 21 is clamped to the negative voltage Vbb as in this embodiment, the charge generated when the activated word line 21 is deactivated is a negative voltage. It flows to the Vbb node and NMOSFET7
9 to another word line 21, and as a result, the memory cell transistor M connected to the other word line 21.
The gate potential of T rises, causing leakage of accumulated charges,
There is a problem that data retention characteristics deteriorate. Therefore, in this embodiment, when the signal XE falls, the word line 21
Instead of immediately lowering the potential of the (selection signal line SX1) from the Vcc level to the Vbb level, the control circuit unit 66a temporarily changes the potential of the selection signal line SX1 to the ground voltage in response to the fall of the signal XE. Vss (0
Since the voltage is held at the V) level, the voltage is reduced to the negative voltage Vbb. During this hold period, most of the charges accumulated on the word line 21 flow into the ground potential. Therefore, even if charges are newly generated when the voltage is lowered to the level of the negative voltage Vbb thereafter, the total charge amount is small, so that the gate potential of the memory cell transistor MT connected to the word line 21 is reduced. The rise is suppressed, and as a result, it is possible to prevent the deterioration of the data retention characteristic due to the leakage of the stored charges.

According to the semiconductor memory device of the present invention,
Since the switching field-effect transistor for connecting the bit line extending from the memory cell array to the sense amplifier can be reliably turned on / off in a narrow operation range, the capability and scale of the driving circuit can be reduced. Thus, area saving can be realized. The present invention can be applied not only to a logic circuit and a DRAM integrated on a semiconductor substrate, but also to a DRAM alone.

[0099]

According to the semiconductor memory device of the present invention, the first switching transistor for connecting the bit line and the sense amplifier can be reliably connected in a narrow operating range.
Since N / OFF can be performed, the capability and scale of the driving circuit can be reduced, and the area can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing a layout of a semiconductor memory device according to an embodiment of the present invention.

FIG. 2 is a partial plan view of the semiconductor memory device shown in FIG. 1;

FIG. 3 is a block diagram showing a circuit configuration of the semiconductor memory device shown in FIG. 1;

FIG. 4 is a partial plan view showing a layout of the sub-array shown in FIG. 3;

FIG. 5 is a sectional view showing a manufacturing process of the semiconductor memory device shown in FIG. 1;

FIG. 6 is a sectional view showing a manufacturing process of the semiconductor memory device shown in FIG. 1;

FIG. 7 is a sectional view showing a manufacturing process of the semiconductor memory device shown in FIG. 1;

FIG. 8 is a circuit diagram of the sub-array shown in FIG.

FIG. 9 is a circuit diagram of a sense amplifier band shown in FIG. 3;

FIG. 10 is a block diagram of a row decoder shown in FIG. 3;

FIG. 11 is a circuit diagram of a first row address detection circuit and a word line selection circuit shown in FIG.

FIG. 12 is a block diagram showing supply of a negative voltage to the word line driver and the logic circuit shown in FIG. 11;

13 is a circuit diagram of a redundant circuit that can be replaced with the first row address detection circuit and the word line selection circuit shown in FIG.

14 is a circuit diagram of a second row address detection circuit and a control selection circuit shown in FIG.

FIG. 15 is a timing chart showing an operation of the control circuit shown in FIG. 14;

FIG. 16 is a circuit diagram showing another example of the control circuit unit in FIG.

FIG. 17 is a plan view showing a well arrangement of the semiconductor memory device shown in FIG. 1;

18 is a timing diagram of the semiconductor memory device shown in FIG.

FIG. 19 is a circuit diagram showing a potential state of the memory cell shown in FIG. 8;

FIG. 20 is a cross-sectional view showing a manufacturing process of a conventional semiconductor memory device.

FIG. 21 is a sectional view showing a manufacturing process of a conventional semiconductor memory device.

FIG. 22 is a cross-sectional view showing a manufacturing process of a conventional semiconductor memory device.

[Explanation of symbols]

 Reference Signs List 31 semiconductor memory device 15 bit line 21 word line 25 Pa, 25 Pb P-channel sense amplifier 25 N N-channel sense amplifier 32 sub-array 33 memory cell array 34 column decoder 35 sense amplifier band 36 local power supply line 49, 50 switching transistor 51 N-channel driving transistor 58, 59 switching transistor 62 drive transistor 63 first row address detection circuit 66 control circuit 70 word line driver 151, 152 common bit line MC memory cell capacitor MT memory cell transistor

Claims (16)

[Claims] 1. A bit line (15) extending from a memory sub-array (32a) including a memory cell transistor (MT).
a1, 15a2) and the first sense amplifier (25 Pa, 2
5N), wherein the first switching transistor (49, 50) for connection to the memory sub-array (32a) is arranged on the opposite side of the input side of the sense amplifier (25) from the memory sub-array (32a). apparatus. 2. The first sense amplifier (25 Pa, 2
5N) is the first P-channel sense amplifier (25 Pa)
And an N-channel sense amplifier (25N), wherein the first switching transistor (49, 50) is arranged between the first P-channel sense amplifier (25Pa) and the N-channel sense amplifier (25N). 2. The semiconductor memory device according to claim 1, wherein the two are separated and connected. 3. A first common bit line (151), a second common bit line (152) complementary to the first common bit line (151), and the first and second common bits Lines (151, 152)
An N-channel sense amplifier (25N) connected therebetween; a first bit line (15a1); a second bit line (15a2) complementary to the first bit line (15a1); And second bit lines (15a1, 15a2)
The first P-channel sense amplifier (25P
a), a first switching transistor (49) connected between the first common bit line (151) and the first bit line (15a1), and a second switching bit line (152). ) And the second bit line (15a2), a second switching transistor (50), a third bit line (15b1), and a complementary to the third bit line (15b1). A fourth bit line (15b2), and the third and fourth bit lines (15b1, 15b2)
The second P-channel sense amplifier (25P
b), a third switching transistor (58) connected between the first common bit line (151) and the third bit line (15b1), and the second common bit line (152). ) And the fourth bit line (15b2), a fourth switching transistor (59), a word line (21), a memory cell capacitor (MC), and the first bit line (15). 15a1) and the memory cell capacitor (MT), and the word line (2
1. A semiconductor memory device comprising: a memory cell transistor (MT) having a gate connected to 1). 4. The memory cell transistor (MT)
Are the first switching transistors (49, 5).
4. The semiconductor memory device according to claim 1, wherein the semiconductor memory device has a lower threshold value than the threshold value of 0). 5. An N-channel drive transistor (51) connected between a power supply node (36) and said first P-channel sense amplifier (25Pa). The semiconductor memory device according to claim 1. 6. The N-channel drive transistor (5)
1) is the first switching transistor (49,
The semiconductor memory device according to claim 5, having a threshold value lower than the threshold value of (50). 7. The N-channel drive transistor (5)
6. The semiconductor memory device according to claim 5, wherein 1) has a threshold value substantially equal to a threshold value of said memory cell transistor (MT). 8. The N-channel drive transistor (5)
The power supply voltage (Vcc) and the ground voltage (V
The semiconductor memory device according to claim 5, further comprising a control circuit configured to selectively apply ss). 9. The sense amplifier (25Pa, 25P)
b, 25N) includes two cross-connected sense transistors (45, 46, 60, 61, 47, 48), and each of the sense transistors (45, 46, 60, 6).
1, 47, 48), the memory cell transistor (M
T), and the switching transistor (49, 5).
4. The semiconductor memory device according to claim 3, wherein (0, 58, 59) have gate insulating films of the same thickness. 10. The memory cell transistor (MT)
4. The semiconductor memory device according to claim 1, further comprising a grounded back gate. 11. A second P-channel sense amplifier (25Pb) is connected to a memory sub-array (32b) complementary to the memory sub-array (32a), and the second P-channel sense amplifier (25Pb) And the N
4. The semiconductor memory device according to claim 3, wherein a second sense amplifier (25Pb, 25N) is configured with the channel sense amplifier (25N). 12. A second switching transistor (58, 59) disposed between the second P-channel sense amplifier (25Pb) and the N-channel sense amplifier (25N) for separating and connecting the two. The semiconductor memory device according to claim 6, wherein the semiconductor memory device is provided. 13. A power supply line (36), a ground line (37), and a plurality of memory cell arrays (MA00 to MAxy). Each of the memory cell arrays (MA00 to MAxy) includes a plurality of bit line pairs (MA00 to MAxy). Subarray (32) containing 15)
And a sense amplifier band (3) adjacent to the sub-array (32).
5), wherein the sense amplifier band (35) includes a plurality of P-channel sense amplifiers (25Pa, 25Pb) respectively connected to the plurality of bit line pairs (15).
And the plurality of P-channel sense amplifiers (25 Pa, 25 P
b), and P-channel sense amplifiers (25 Pa, 25 P) each corresponding to the power supply line (36).
b), a plurality of N-channel sense amplifiers (25N) respectively connected to the plurality of bit line pairs (15), and a plurality of N-channel sense amplifiers (25N) connected to the plurality of bit line pairs (15). A plurality of ground drive transistors (52) provided corresponding to the channel sense amplifiers (25N), each connected between the ground line (37) and the corresponding N-channel sense amplifier (25N). A semiconductor memory device characterized by the above-mentioned. 14. The memory cell array (MA0)
0 to MAXy) are arranged in a matrix, and the memory cell array (MA00) arranged in each row of the matrix
To MAXy) in the power supply driving transistors (51, 6).
2) are commonly connected to the power supply line (36), and are connected to the memory cell array (MA) arranged in each row of the matrix.
00 to MAXy).
2) are commonly connected to the ground line (37), and are connected to the memory cell array (MA) arranged in each column of the matrix.
00 to MAXy).
1, 62) are commonly connected to the power supply line (36), and the ground drive transistors (52) in the memory cell arrays (MA00 to MAxy) arranged in each column of the matrix are connected to the ground line (37). 14. The semiconductor memory device according to claim 13, wherein the semiconductor memory device is commonly connected to the semiconductor memory device. 15. A semiconductor substrate (1); a dynamic random access memory formed on the semiconductor substrate (1); and a dynamic random access memory formed on the semiconductor substrate (1) for controlling the dynamic random access memory. A memory cell capacitor (MC) in the dynamic random access memory has a capacitance insulating film (202) having substantially the same thickness as a gate insulating film (3) of a transistor constituting the logic circuit. A semiconductor memory device. 16. The memory cell capacitor (MC)
16. The semiconductor memory device according to claim 15, wherein the device has a cell plate electrode (13) grounded.