JP2001283584A - Semiconductor memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric memory having similar constitution to a SRAM and also having high integration, high reliability, and high speed characteristics. SOLUTION: This memory comprises flip-flop circuits provided at intersections of plural word lines (WL13, WL13B) and data lines (DL13, DL13B), and in which accumulation electrodes of two capacitors are coupled respectively to information accumulation node (ST13, ST13B). a first potential and a second potential are applied to the accumulation electrodes of the capacitors, while a third potential (Vcc/2) is applied to a plate electrodes of the capacitors. The flip-flop circuit comprises a first inverter having a first input node (ST13) and a first output node (ST13B) and a second inverter making two nodes connected to the ST13 and the ST13B as a second input node and a second output node. On the other hand, the accumulation electrode of the one side of capacitors is connected to the ST13 and the accumulation electrode of the other side of capacitors is connected to the ST13B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonvolatile semiconductor memory using a ferroelectric material, and more particularly, to a ferroelectric material capable of retaining the latest information as nonvolatile information and realizing high integration, high reliability and high-speed operation. Regarding memory.

[0002]

2. Description of the Related Art Ferroelectric memories, ferroelectric random access memories (FERA)
M) is a nonvolatile memory that stores data in the polarization direction of the ferroelectric. FIG. 2 shows an example of such a FERAM.
This shows an array configuration described in JP-A-3-283176. Like a conventional dynamic random access memory (DRAM), a memory cell is composed of one transistor and one capacitor. To write nonvolatile information in a desired cell, a transistor is selectively turned on, one electrode of a desired capacitor is connected to a data line, for example, DL (j), and DL (j) is set to 0 or Vcc. I do. Then, since the plate line is at the potential of Vcc / 2, an electric field is selectively applied to a desired ferroelectric capacitor, and polarization corresponding to nonvolatile information is generated. This polarization direction is not lost even when the power is turned off as a characteristic of the ferroelectric substance. On the other hand, in order to read the nonvolatile information of the cell, for example, the data line DL (j) is charged to 0 V, the cell is brought into a floating state, and then the transistor is selectively turned on. Then, since the plate line is at the potential of Vcc / 2, an electric field is applied to the selected ferroelectric capacitor. This electric field is always in a fixed direction, and there are a case where the polarization direction of the ferroelectric is maintained as it is and a case where it is reversed according to the nonvolatile information. When the polarization is reversed, a large current flows into the memory cell. This inflowing current is described in, for example, Japanese Patent Application Laid-Open No. 3-283.
If the detection is performed by the method described in Japanese Patent Publication No. 176, the nonvolatile information can be read. However, as is clear from the above description, every time the nonvolatile information is read, the polarization direction of the ferroelectric is aligned in one direction, so that the information needs to be rewritten. Then, when the memory is in the storage state of the direction in which the polarization is inverted, it is necessary to perform two polarization inversions every time the read operation is performed. On the other hand, it is known that the ferroelectric capacitor deteriorates every time the polarization is inverted, and eventually it becomes impossible to maintain the polarization when no voltage is applied. Therefore, in order for the FERAM to be a highly reliable nonvolatile memory, the number of times of polarization inversion should be as small as possible. Another problem is that a certain period of time is required for reversing the polarization, and the reading speed is accordingly reduced. As a method of solving the problem of the deterioration of the ferroelectric film due to the polarization inversion and the reduction of the reading speed,
JP-A-3-283176 proposes the following method. That is, during normal operation, the plate wire
For example, it is set to Vcc and used as a DRAM, and stored as nonvolatile information by the FERAM write operation before the power is turned off. If the plate line is set to Vcc, the information does not invert in any case with respect to the potential 0 or Vcc of the storage portion, and therefore, the problem of deterioration of the ferroelectric capacitor can be avoided and the reading speed does not decrease. . Next, when the power is turned on, if the nonvolatile information is read by the FERAM operation, the nonvolatile memory can be effectively functioned.

[0003]

However, the above D
The RAM / FERAM dual-purpose system has a problem in that the operation of converting volatile information into nonvolatile information is complicated. That is, for all the memory cells, information is first read out by DRAM operation, and then FERA is read in accordance with the information.
It must be stored as nonvolatile information in the M operation. In particular,
When the power supply is turned off due to an accident, it is extremely difficult to quickly terminate the above conversion operation. Since the polarization of the ferroelectric material is all aligned in one direction during the period of using the DRAM in the above method,
With accidental power-off, all stored information is lost. In addition, when the present memory is used in a small system such as a portable device, there is a problem that a redundant termination procedure using a backup power supply or the like when the power is turned off is not desirable. As a method for solving such a problem, a static random access memory (SR)
AM) and FERAM are proposed in, for example, Japanese Patent Application Laid-Open No. 1-68699.
In this method, a ferroelectric capacitor is connected to each of two storage nodes of an SRAM via a transistor. During normal operation, the transistor is turned off to operate as an SRAM, and if necessary, the transistor is turned on and connected to a ferroelectric capacitor to store it as nonvolatile information. Even if the power is turned off due to an unexpected accident, at least the most recently stored nonvolatile information is maintained, so that the next operation may be resumed from that point. However, this method requires an extra transistor for separating the volatile memory and the non-volatile memory, and has a problem that the area of the memory cell is increased. An object of the present invention is to solve such a problem and provide a D
Despite having the same structure as one RAM and one transistor and one capacitor, deterioration of the ferroelectric capacitor due to polarization reversal can be mitigated, and the latest information is retained as nonvolatile information even when the power is turned off due to an unexpected accident.
An object of the present invention is to provide a nonvolatile memory (ferroelectric memory) with high integration, high reliability and high-speed operation. Another object of the present invention is to provide a highly reliable and high-speed non-volatile memory (ferroelectric memory) having a memory cell configuration similar to that of an SRAM without an extra transistor.

[0004]

To achieve the above object, a ferroelectric memory according to the present invention is a semiconductor memory having a plurality of memory cells each including at least one transistor and one ferroelectric capacitor. Normally, a read / write operation is performed as a volatile memory, for example, a DRAM, and means (a precharge circuit, a power supply potential detection circuit, a plate potential supply circuit, etc.) for quickly setting the plate potential to the ground potential (0 V) when the power is off is provided. The feature is that it is provided. However, the plate potential is Vcc / 2, and the data line precharge potential at the time of reading is also Vcc / 2. Further, in order to further improve the reliability, a configuration in which the plate is common only to the memory cells connected to the common word line (a configuration having a plurality of plate lines), or the above means is provided in the SRAM There is a characteristic in having done it. The present memory is applied to a system in which the number of times of reading is larger than the number of times of rewriting, for example, storage of data when the calculation is performed based on the program or storage of the program itself.

[0005]

In the present invention, the read operation is performed by detecting the voltage of the storage node as in the case of a volatile memory, for example, a DRAM. This voltage sensing and amplification
Plate potential and data line precharge potential to Vcc
Since the effect is set without polarization inversion as the effect set at / 2, there is no problem of deterioration of the ferroelectric film and reduction of the reading speed. In addition, the polarization direction holds the latest information that has been most recently rewritten. In other words, the volatile information as the storage node potential always matches the nonvolatile information as the polarization direction of the ferroelectric film. The rewriting operation involves polarization inversion, but the number of rewritings is limited by, for example, an electrically erasable programmable read only memory (EEPR).
The limit envisaged in OM) is expected to be more than 10 ¹¹ times, much larger than 10 ⁶ times, so that it can be applied without problems to many systems. For example, the present invention can be applied to storage of data or the program itself in which calculation is performed based on a program, in which the number of times of reading is generally larger than the number of times of rewriting. When the power supply is turned off, before the potential of the storage node drops from Vcc to 0 V, by providing means for rapidly reducing the plate potential from Vcc / 2 to 0 V, the polarization direction is maintained and the most recent rewriting is performed. The latest nonvolatile information can be left. Next, when the power is turned on, if the nonvolatile information stored as the polarization direction in the ferroelectric film is amplified to the data line in accordance with the read operation of the FERAM, it can be converted into volatile information as the potential of the storage node. . That is, a highly integrated, highly reliable, and high-speed nonvolatile memory can be realized.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing an array configuration of a ferroelectric memory according to a first embodiment of the present invention. The memory cell M1 according to the present embodiment includes one transistor and one ferroelectric capacitor. The potential of the plate PL1 of the ferroelectric capacitor is always fixed at Vcc / 2.
On the other hand, the storage node ST1 of the ferroelectric capacitor holds the volatile information Vcc or 0. Data line pair DL1
The potentials of (j) and DL1 (j) B are held at Vcc / 2 by the precharge circuit PC1 (j) until immediately before the read or rewrite operation. A sense amplifier SA1 (j) for detecting and amplifying stored information is provided on the data line pair.
Is connected. This array has a dummy cell DM1 for reading out the polarization direction of the ferroelectric film when the power is turned on, and converting the nonvolatile information into volatile information. Also,
The signal line GWL1 and the transistor connected thereto are:
It is used to precharge a data line pair to 0 V when performing a read operation of nonvolatile information.

FIG. 3 is a timing chart showing a stored information reading operation in the memory cell array of FIG. In this embodiment, to detect the storage voltage of the storage node ST1, first, the potential of the precharge control line PCL1 is changed from Vcc to 0. As a result, the data line has the potential Vcc.
/ 2 floating state. Next, the word line WL
The potential of 1 (i) is increased from 0 to Vch. Where V
ch is a potential higher than Vcc by at least the threshold voltage of the transistor. As a result, when the potential of the storage node is Vcc, the potential of data line DL1 (j) becomes slightly higher than the potential of DL1 (j) B, that is, Vcc / 2. , DL1 (j) are slightly lower than DL1 (j) B. By detecting and amplifying this potential difference with the sense amplifier SA1 (j), the potential of DL1 (j) matches the potential of the storage node and becomes Vcc or 0. The potential of DL1 (j) B is DL
The potential becomes opposite to 1 (j). To operate the sense amplifier, the sense amplifier p-channel transistor control line SAP1 and the sense amplifier n-channel transistor control line SAN1 may be set to Vcc and 0, respectively.
Through the above operation, information of all the memory cells connected to the selected word line WL1 (i) is read out to the data lines connected to the respective memory cells. In order to selectively read information of one of the memory cells to the outside via the IO line, the potential of the sense amplifier select line YS1 (j) is changed from 0 to Vch, and a desired data line is connected to the IO line. Just do it. To end the read operation, the potential of YS1 (j) is returned from Vch to 0, and then the word line WL1 (i) is set to 0.
, The storage node ST1 is electrically disconnected from the data line in a state where the information is rewritten. PCL1 is set to Vcc, SAP1 and SAN1 are set to 0 and Vc, respectively.
If it returns to c, it will be in the state before the read operation, and the operation will end. According to the present embodiment, the polarization direction stored in the ferroelectric film corresponding to the potential of the storage node before the read operation does not reverse during the read operation. Because
This is because an electric field in the direction of inverting the polarization is not applied to the ferroelectric capacitor during the read operation. Therefore, deterioration of the ferroelectric film due to the reading operation can be avoided. Further, there is no decrease in the reading speed due to the time required for the polarization reversal. Moreover, the stored information is
It is always held not only as volatile information of the storage node but also as nonvolatile information corresponding to the polarization direction of the ferroelectric film. Therefore, information is not lost even when the power is turned off. Thus, according to the present embodiment, high integration,
A highly reliable and high-speed nonvolatile memory can be obtained.

FIG. 4 is a timing chart showing an information rewriting operation in the memory cell array of FIG. In the rewriting of information in the present embodiment, the storage node ST1
And the polarization inversion of the ferroelectric film. FIG.
In the rewriting operation of FIG. 3, from the time when the signal line PCL1 is lowered from Vch to 0 to the time when the sense amplifier is operated, FIG.
This is the same as the read operation described above. Next, the signal line YS1 (j) is raised from 0 to Vch to write the rewrite information prepared on the IO line to the memory cell. As a result,
The potentials of the data line pair DL1 (j) and DL1 (j) B are inverted. Since the word line WL1 (i) is in an activated state, the potential of the storage node of the desired memory cell and the polarization direction of the ferroelectric film are inverted with the above-described potential inversion of the data line pair. After rewriting information in this way, the rewriting operation is completed in the same procedure as in FIG. According to the embodiment of the present invention, the volatile information and the nonvolatile information are always rewritten so as to be consistent with each other, so that there is an effect that a highly reliable nonvolatile memory is obtained in which the information is not lost even when the power is turned off. Note that, in order to easily invert the potential latched by the sense amplifier by activating the signal line YS1 (j), the word line WL1 (i) is inactivated once to reduce the load on the data line, and then the data line potential is reduced. May be inverted, and then the word line is activated again to invert the memory cell information.

FIG. 5 is a timing chart showing a conversion operation from nonvolatile information to volatile information when the power is turned on in the memory cell array of FIG. In this embodiment,
Prior to power up, all potentials are at 0V. When the power is turned on, the plate PL1 is initialized to Vcc / 2, and the signal lines SAP1 and SAN1 of the sense amplifier are initialized to 0 and Vcc. The potential of the signal line PCL is 0 to V
cc, and as a result, the data line pair DL1
(J), the potential of DL1 (j) B is precharged to Vcc / 2. At this time, the word line potential is kept at 0 V, and the storage node ST1 is set in a floating state so that the polarization direction of the ferroelectric film is not destroyed at the time of boosting the plate. Plate PL1 and data line pair DL1 (j), D
When the potential of L1 (i) B is reliably stabilized at the potential of Vcc / 2, the word line WL1 (i) (i = 1, 2,...)
n) are sequentially activated, and the storage node ST1 is switched to the plate PL.
The potential of Vcc / 2, which is the same as 1, makes the retention of polarization information more stable. Subsequent to the initialization operation described above, the operation shifts to a conversion operation from nonvolatile information to volatile information. First, the potential of PCL1 is set to 0V while the word lines are all at 0V, and the data lines are set to the floating state. Next, the signal line GWL1 is activated, and the data line is precharged to 0 V and brought into a floating state again. Thereafter, when the word line WL1 (i) is activated, a current flows from the storage node ST1 to the data line, and the data line potential rises. The amount of the rise depends on the polarization direction of the ferroelectric film. That is, since the plate potential is still higher after the data line potential rises, the polarization direction is aligned in one direction. In the case where the word line activation involves polarization inversion,
The effective ferroelectric capacitor capacitance is large,
The data line potential rise is also large. The initial polarization direction of the ferroelectric film can be known from the data line potential rise. Specifically, a dummy cell DM1 for generating an intermediate value of the data line potential increase amount corresponding to the two polarization states on the complementary data line DL1 (j) B is provided, and the data line pair DL1 (j) is provided.
The potential difference between DL1 (j) B and the sense amplifier SA1 (j)
And then amplify. The capacitor of the dummy cell is, for example, a paraelectric capacitor having an appropriate capacity to generate the above-mentioned desired potential rise. As a result of the data line potential being charged to Vcc or 0 by the operation of the sense amplifier, volatile information is written to the storage node ST1. Finally, after deactivating the word line, the potential of the data line is changed to Vcc / 2.
To end the series of operations. The above operation is performed on the word line W
By sequentially performing L1 (i) (i = 1, 2,... N), the conversion operation from the nonvolatile information to the volatile information is completed. According to the present embodiment, the reversal of the polarization of the ferroelectric film due to the information reading operation can be performed only when the power is turned on, so that the deterioration of the ferroelectric film can be reduced. In addition, during normal use, there is no decrease in the reading speed due to the time required for the polarization reversal. Moreover, the information at the time when the power is turned off is stored, and the information can be restored when the power is turned on next time. Thus, according to the present embodiment, a highly reliable and high-speed nonvolatile memory can be obtained.

FIG. 6 is a timing chart showing a basic initial operation to be performed first when the power is turned on in the ferroelectric memory array of FIG. In the present embodiment, it is detected that the power supply voltage has risen to a certain level or more by turning on the power supply. When this is confirmed, the voltage of the plate PL1 is changed to V
cc / 2, for example, the process of converting non-volatile information to volatile information described with reference to FIG. On the other hand, the word line potential is maintained at 0 V from when the power is turned on until at least the end of the supply of the plate potential. According to this embodiment, when the plate voltage is boosted, the storage node is always in a floating state, so that an electric field enough to change the polarization direction is not applied to the ferroelectric capacitor,
Therefore, the nonvolatile storage information held in the ferroelectric memory before the power is turned on is not destroyed by the operation accompanying the power on. Thus, according to the present embodiment,
A highly reliable nonvolatile memory can be obtained.

FIG. 7 is a timing chart showing a basic termination operation to be performed when the power is turned off in the ferroelectric memory array of FIG. In this embodiment, when the power supply is turned off intentionally or unexpectedly, the power supply voltage detection circuit for detecting that the power supply voltage has fallen below a certain level is activated, and the end operation is started. First, all word lines WL1 (i) are set to 0V. Next, the voltage on plate PL1 is quickly discharged from Vcc / 2 to 0V. According to the present embodiment, when the potential of the storage node is, for example, Vcc, the plate potential can be set to 0 V before the potential of the storage node is slowly discharged to 0 V due to a junction leak current or the like. Therefore, even if the power is turned off intentionally or unexpectedly, the nonvolatile memory information is not destroyed. As described above, according to the present embodiment, a highly reliable nonvolatile memory can be obtained with a simple end operation. It is to be noted that the operation of FIG. 7 effectively functions even for a certain kind of noise in which the power supply voltage drops for a certain period of time and recovers again, and there is an effect that a highly reliable ferroelectric memory can be obtained. Needless to say. As the power supply voltage detection circuit used in the operations of FIGS. 6 and 7, for example, a circuit having the characteristics of FIG. 8 may be used. With a constant voltage lower than the normal use voltage Vcc as a boundary, the output Vout of the power supply voltage detection circuit becomes substantially 0 V below that voltage, and becomes equal to the power supply voltage above that voltage. As a specific circuit, for example, as shown in FIG. 9, a differential amplifier may be used.

FIG. 10 shows the structure of the ferroelectric memory array shown in FIG.
FIG. 4 is a diagram showing a plate potential supply circuit in the embodiment. This embodiment
Plate is an n-channel field effect transistor TR₁
And connected to the level of Vcc / 2 at the same time,
p-channel field effect transistor TR _TwoThrough the gra
Connected to the ground level 0V. Transistor common game
Is connected to a terminal at the same potential level as the power supply or the power supply.
Connected to the output terminal of the pressure detection circuit. When the power is on
The gate voltage of the p-channel transistor becomes Vcc.
Plate is electrically disconnected from ground level
You. When the power is turned off, the n-channel transistor
The plate voltage becomes 0V and the plate is at the level of Vcc / 2.
From the p-channel transistor.
When the gate voltage of the transistor becomes 0 V, the p-channel
When the tunneling transistor turns on, the plate potential quickly becomes zero.
Fall to V. Here, the parasitic capacitance applied to the gate
As small as possible, and immediately turn to 0 V when the power is turned off.
To be. According to the present embodiment, the power supply
Drop the plate voltage to 0V immediately when off
The polarization of the ferroelectric film even when the power is suddenly turned off.
May not be reversed, thus destroying information.
And a highly reliable ferroelectric memory with no problem.

FIG. 11 shows a second embodiment of the present invention.
FIG. 3 is a diagram showing an array configuration of a ferroelectric memory in the example of FIG. While the plate is common to all the memory cells in the first embodiment (FIG. 1), FIG.
Are common only to memory cells connected to a common word line, and a plurality of plate lines PL10 (i),
PL10 (i + 1). In this embodiment, during normal use, it is used as a volatile memory in the same manner as in FIGS. On the other hand, during the conversion operation from the nonvolatile information to the volatile information when the power is turned on, only the plate line of the memory cell connected to the activated word line is selectively boosted by the operation method described below. To read out the nonvolatile information.

FIG. 12 is a timing chart showing a conversion operation from nonvolatile information to volatile information at the time of power-on in the memory cell array of FIG. In this embodiment, all the nodes are at the ground level 0 V immediately after the power is turned on. First, the signal line SAN10 is set to Vcc to deactivate the sense amplifier, and the ground word line G
By setting WL10 to Vcc, the potential of the data line pair is surely set to 0V.
To After the GWL10 is returned to 0V and the data line pair is brought into a floating state, the word line WL10 (i) is activated. Next, when the plate line of the memory cell group connected to the word line is boosted to Vcc / 2, the data line is boosted via the ferroelectric capacitor. Since this potential boosting amount differs depending on the polarization direction of the ferroelectric capacitor, the nonvolatile information can be read out by detecting this. At this time, a dummy cell similar to that described with reference to FIG. 5 is provided on the complementary data line DL10 (j) B side so as to generate a reference voltage. The small voltage difference between the data line pair is amplified by activating the sense amplifier by the signal lines SAN10 and SAP10. Finally, when the word line is deactivated and the sense amplifier is also deactivated, the operation of converting the nonvolatile information into the volatile information ends. The above conversion operation is performed for all the word lines WL10 (i) (i = 1,
2), all nonvolatile information can be converted to volatile information. However, after the power is turned on, in the second and subsequent word line activations, as shown by the dotted line in FIG.
To 0. In FIG. 12,
Each time the conversion operation for one word line is completed, the signal line PCL10 is activated, and the data line is precharged to Vcc / 2. Accordingly, in the second and subsequent word line activations, first, the PCL 10 is deactivated, and then the GWL 10
To lower the data line potential from Vcc / 2 to 0. However, it is not always necessary to activate the signal line PCL10 every time the conversion operation for one word line is completed. According to the present embodiment, when the voltage of the plate line is boosted, the polarization direction of the ferroelectric capacitor connected to the plate line is always detected, so that the conversion operation from the nonvolatile information to the volatile information can be stably performed. . In other words, there is no necessity to destroy the information of the non-selected ferroelectric capacitor while reading the nonvolatile information of a certain ferroelectric capacitor.

(Third Embodiment) FIG. 13 shows a third embodiment of the present invention.
FIG. 3 is a diagram showing an array configuration of a ferroelectric memory in the example of FIG. When storing volatile information in the ferroelectric memory of this embodiment, one memory cell is used as one storage unit, whereas when storing nonvolatile information, two memory cells are used as one storage unit. Then, polarizations in opposite directions are recorded in the ferroelectric capacitors of the two memory cells. Reading of the nonvolatile information is performed in the same manner as in the operation method of FIG. However, a dummy cell is not used, and word lines WL12 (i) and WL12 (i + 1) connected to two memory cells are used.
Are activated simultaneously. The read non-volatile information is complementarily converted into two memory cells as volatile information. That is, the storage voltages correspond to the polarization directions of the respective ferroelectric capacitors. During normal operation as a volatile memory, only one of the two memory cell storage information is sufficient, and the other one of the memory cells stores storage information that is necessary only for temporary calculations and does not need to be left as non-volatile information. Can be used. According to the present embodiment, no dummy cell is required when reading nonvolatile information, and the operation as a nonvolatile memory can be performed more stably.

(Fourth Embodiment) FIG. 14 shows a fourth embodiment of the present invention.
FIG. 3 is a diagram showing a ferroelectric memory cell in the embodiment of FIG.
Static random access memory (SRA
This forms a ferroelectric memory having a configuration similar to M). In the present embodiment, complementary storage nodes ST13 and ST13B each constituted by a flip-flop include:
Each is connected to a ferroelectric capacitor. The plate voltage of the ferroelectric capacitor is almost half the value Vc of the power supply voltage.
c / 2. According to the present embodiment, ST13 and ST13
When reading volatile information as the voltage of 13B, the polarization of the ferroelectric capacitor does not reverse. When rewriting volatile information, the polarization direction is also reversed. Therefore, the volatile information always coincides with the nonvolatile information as the polarization direction of the ferroelectric capacitor, and there is an advantage that the information can be retained even when the power is turned off. Further, since the polarization inversion can be minimized only at the time of rewriting information, fatigue of the ferroelectric film can be reduced, and a highly reliable ferroelectric memory can be obtained.

[0017]

According to the present invention, a high-integration, high-reliability, high-speed ferroelectric memory is provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an array configuration of a ferroelectric memory according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an array configuration of a conventional ferroelectric memory.

FIG. 3 is a timing chart showing a stored information read operation in the memory cell array of FIG. 1;

FIG. 4 is a timing chart showing an information rewriting operation in the memory cell array of FIG. 1;

5 is a timing chart showing a conversion operation from nonvolatile information to volatile information when power is turned on in the memory cell array of FIG. 1;

6 is a timing chart showing a basic initial operation to be performed first when power is turned on in the ferroelectric memory array of FIG. 1;

FIG. 7 is a timing chart showing a basic end operation to be performed when power is turned off in the ferroelectric memory array of FIG. 1;

FIG. 8 is a diagram showing output characteristics of the power supply voltage detection circuit according to the first embodiment of the present invention.

FIG. 9 is a diagram illustrating a configuration of a power supply voltage detection circuit according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a plate potential supply circuit according to the first embodiment of the present invention.

FIG. 11 is a diagram showing an array configuration of a ferroelectric memory according to a second embodiment of the present invention.

12 is a timing chart showing a conversion operation from nonvolatile information to volatile information at the time of power-on in the memory cell array of FIG. 11;

FIG. 13 is a diagram showing an array configuration of a ferroelectric memory according to a third embodiment of the present invention.

FIG. 14 is a diagram showing a ferroelectric memory cell according to a fourth embodiment of the present invention.

[Explanation of symbols]

DLn (j) Data line WLn (i) Word line WLn (i) B Complementary word line DWLn Dummy word line DWLnB Complementary dummy word line GWLn Grounding word line PCn (j) Precharge circuit PCLn Precharge control line SAn (j) Sense Amplifier SAPn Sense amplifier p-channel transistor control line SANn Sense amplifier n-channel transistor control line IOn I / O line IOnB Complementary I / O line YSn (j) Sense amplifier selection line Mn Memory cell STn Storage node DMn Dummy cell PL10 (i) Plate line DPL10 Dummy Plate line TR ₁ n-channel field-effect transistor TR ₂ p-channel field-effect transistor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H01L 27/105 (72) Inventor Yoshinobu Nakagome 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi, Ltd. In-house (72) Inventor Masakazu Aoki 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd.

Claims (2)

[Claims] 1. Two capacitors provided at intersections of a plurality of word lines and a plurality of data lines and using a ferroelectric material as an insulating film, and storage electrodes of the two capacitors are respectively coupled to their information storage nodes. A plurality of memory cells including a flip-flop circuit to be applied; a means for applying a first potential or a second potential to a storage electrode of a capacitor of each of the plurality of memory cells; A semiconductor memory, comprising: means for applying a third potential, which is a potential between the first potential and the second potential, to a plate electrode of a capacitor of a memory cell. 2. The semiconductor memory according to claim 1, wherein said flip-flop circuit comprises: a first inverter having a first input node and a first output node; and a second input node connected to said first output node. A second inverter having a second output node connected to the first input node, wherein the storage electrode of one of the two capacitors is connected to the first input node, and The semiconductor memory, wherein the storage electrode is connected to the first output node.