Abstract:
A polarization transfer device includes a ferroelectric thin film formed continuously as one piece; a plurality of polarization switches formed by placing the ferroelectric thin film between a first gate electrode and a second gate electrode; and a plurality of polarization accumulators formed by placing the ferroelectric thin film between a first electrode plate and a second electrode plate, wherein the plurality of polarization switches and the plurality of polarization accumulators are arranged alternately.

Description:
The entire disclosure of Japanese Patent Application No. 2006-016068, filed Jan. 25, 2006 is expressly incorporated by reference herein. 
   BACKGROUND 
   1. Technical Field 
   The present invention relates to the field of devices which use non-volatility of ferroelectric material. More particularly, it relates to a configuration of a functional block which acts as an element of device configuration to transfer polarization when using polarization of ferroelectric material as memory elements. 
   2. Related Art 
   Recently, in the field of memories, non-volatile memories which are electrically writable and erasable have been growing in importance. There are various types of non-volatile memory, but ferroelectric memories have been receiving attention because of their high speed, low voltage characteristics, and low power consumption. 
   For example, as shown in  FIG. 43 , a ferroelectric thin film  4340  is placed between an electrode  4341  and electrode  4342  to form a ferroelectric capacitor  4349 , which is used as an element of a memory cell. Besides, there is a so-called 1T1C (1-transistor, 1-capacitor) ferroelectric memory, in which a memory cell consists of an insulated-gate field effect transistor  4412  and ferroelectric capacitor  4411  and the groups of the memory cells are arranged in a matrix on word lines  4413 , bit lines  4414 , and plate lines  4415  as shown in  FIG. 44 . 
     FIG. 42  is a characteristic curve showing a relationship between applied voltage of the ferroelectric capacitor  4349  indicated by a broken line in  FIG. 43  or the ferroelectric thin film  4340  and internal polarization. In  FIG. 42 , when an applied voltage V is applied, reverse polarity polarization is induced in the ferroelectric thin film. This state corresponds to characteristic point  4204 . Subsequently, even if the applied voltage is reduced to 0, residual polarization remains in the ferroelectric thin film, resulting in characteristic point  4205 . Then, when a voltage is applied in the positive direction, the residual polarization disappears, resulting in characteristic point  4206 . Then, when the applied voltage is changed to −V, reverse polarity polarization is induced, resulting in characteristic point  4201 . Then, even if the applied voltage becomes 0, residual polarization remains in the ferroelectric thin film, resulting in characteristic point  4202 . Then, when a voltage is applied in the positive direction, the residual polarization disappears, resulting in characteristic point  4203 . Then, when a positive voltage V is applied, the characteristic curve returns to characteristic point  4204 . Thus, as can be seen from the characteristic curve in  FIG. 42 , ferroelectric material presents hysteresis characteristics depending on the applied direction and history of the applied voltage. Also, the polarization induced by the application of a voltage is retained as residual polarization even if the applied voltage is reduced to 0. The residual polarization does not disappear even if a voltage is applied in the reverse direction, provided that the voltage does not exceed coercive voltage. The above-mentioned hysteresis characteristics and residual polarization feature of ferroelectric material are used for non-volatile memories. 
     FIG. 45  is a sectional view showing a structure of a ferroelectric transistor which is formed as a field effect transistor consisting of a gate electrode  4501 , source electrode  4502 , drain electrode  4503 , and bulk or channel  4509 , and which is provided with a ferroelectric thin film  4500  formed directly underneath the gate electrode  4501 . In the ferroelectric transistor in  FIG. 45 , a threshold voltage of the field effect transistor changes with the polarity and magnitude of the residual polarization of the ferroelectric thin film  4500 , causing a source-drain current to change. 
   Also, there is a ferroelectric memory which makes use of a principle in detecting the residual polarization stored in the ferroelectric thin film  4500  based on difference in the value of current flowing through a ferroelectric transistor  4601  selected according to its address from among ferroelectric transistors as shown in  FIG. 45  arranged in a matrix as shown in  FIG. 46 . 
   Also, there are various other types of ferroelectric memory. However, most of them use either a combination of ferroelectric capacitors and insulated-gate field effect transistors or field effect transistors with a ferroelectric thin film formed in the gate. Thus, they are regarded as basically similar kind and similar type in principle. 
   Incidentally, an example in which a ferroelectric capacitor  4349  or  4411  (such as shown  FIG. 43  or  FIG. 44 ) and insulated-gate field effect transistor  4412  are combined to be used as a memory element is disclosed in JP-A-11-39882. A similar example is disclosed in JP-A-11-177036 although it differs in the method for connecting the ferroelectric capacitor and insulated-gate field effect transistor. 
   Also, examples in which a field effect transistor  4601  with a ferroelectric thin film formed in the gate shown  FIG. 45  or  FIG. 46  is used as a memory element are disclosed in JP-A-11-251586 and JP-A-2004-153239. 
   However, in any of JP-A-11-39882, JP-A-11-177036, JP-A-11-251586, and JP-A-2004-153239, when using as the ferroelectric capacitor or field effect transistor with a ferroelectric thin film formed in the gate, elements must be made independent of each other. For that, the ferroelectric thin film must be separated element by element. Therefore, a technique has been adopted in which the ferroelectric thin film is cut chemically or physically or grown in small areas in isolation. Ferroelectric material varies greatly in characteristics at end points of crystals. Thus, in conventional configuration of ferroelectric memory, when a memory cell is miniaturized to increase the packing density of the device, the ferroelectric thin film must be reduced in size accordingly. However, the characteristics of the ferroelectric material may change with miniaturization as described above. As a result, there are problems that this makes it difficult to accomplish miniaturizing by means of miniaturization, and makes it difficult in turn to achieve high capacity and reduce costs. 
   SUMMARY 
   To solve the above problem, the present invention has an object to maintain characteristics of ferroelectric material high, good and stable regardless of miniaturization or packing density using a ferroelectric thin film formed continuously as one piece. Also, it has an object to provide a ferroelectric memory device with high packing density, high capacity, and low costs by reducing its dimensions (design size) by means of making these characteristics stable. 
   To solve the above problem and achieve the above objects, the present invention has the following aspects. 
   According to a first aspect of the present invention, there is provided a polarization transfer device comprising: a ferroelectric thin film formed continuously as one piece; a plurality of polarization switches formed by placing the ferroelectric thin film between a first gate electrode and a second gate electrode; and a plurality of polarization accumulators formed by placing the ferroelectric thin film between a first electrode plate and a second electrode plate, wherein the plurality of polarization switches and the plurality of polarization accumulators are arranged alternately. 
   According to a second aspect of the present invention, in the first aspect, the first gate electrode of the plurality of polarization switches and the first electrode plate of the plurality of polarization accumulators are constituted of a continuous common electrode. 
   According to a third aspect of the present invention, in the first or second aspect, the second gate electrode of the plurality of polarization switches and the second electrode plate of the plurality of polarization accumulators are formed in different manufacturing processes. 
   According to a fourth aspect of the present invention, in the second aspect, the continuous common electrode is made of platinum. 
   According to a fifth aspect of the present invention, in the first aspect, an insulating layer made of paraelectric material is provided between the ferroelectric thin film and the second electrode of the plurality of polarization switches as well as between the ferroelectric thin film and the second electrode plate of the plurality of polarization accumulators. 
   According to a sixth aspect of the present invention, in the first aspect, a first insulating layer made of paraelectric material is provided between the ferroelectric thin film and the second electrode of the plurality of polarization switches; a second insulating layer made of paraelectric material is provided between the ferroelectric thin film and the second electrode plate of the plurality of polarization accumulators; and the first insulating layer and the second insulating layer differ in dielectric constant. 
   According to a seventh aspect of the present invention, in the fifth aspect, the paraelectric material of the insulating layer is nickel oxide. 
   According to an eighth aspect of the present invention, in the first aspect, the ferroelectric thin film is made of PZTN, PZT, or SBT. 
   According to a ninth aspect of the present invention, a transfer control method controls the polarization transfer device in the first or second aspect, wherein a control voltage applied between the first gate electrode and the second gate electrode of the polarization switches and a control voltage applied between the first electrode plate and the second electrode plate of the polarization accumulators are not higher than coercive voltage of the ferroelectric thin film. 
   According to a tenth aspect of the present invention, a transfer control method controls the polarization in the first or second aspect, wherein a control signal is given so as to apply a voltage between the first electrode plates and/or between the second electrode plates of adjacent first and second polarization accumulators among the plurality of polarization accumulators in such a way as to attract or repel polarization of signals in a direction of transfer. 
   The present invention, configured as described above, provides stable characteristics because the ferroelectric thin film is formed continuously as one piece. 
   Also, the present invention, which accumulates and transfer polarized signals in the ferroelectric thin film, makes signals non-volatile and allows a write circuit or signal detection circuit to be shared, and thereby increases packing efficiency. 
   Also, even if control signals and the metal electrodes of the polarization accumulators are miniaturized, the ferroelectric thin film occupies a large area all the same. Consequently, the present invention gives the ferroelectric thin film stable characteristics which is important for non-volatile memories and makes it relatively easy to achieve miniaturization and high packing density. 
   Thus, the present invention provides a high-density, high-capacity, low-cost ferroelectric memory with stable characteristics. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view showing a structure of a polarization transfer device according to a first embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 2  is a sectional view showing a structure of a polarization transfer device according to a third embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 3  is a sectional view showing a structure of a polarization transfer device according to a fifth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 4  is a sectional view showing a structure of a polarization transfer device according to an eighth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 5  is a sectional view showing a structure of a polarization transfer device according to a tenth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 6  is a sectional view showing a structure of a polarization transfer device according to a second embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 7  is a sectional view showing a structure of a polarization transfer device according to a seventh embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 8  is a sectional view showing a structure of a polarization transfer device according to a fourth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 9  is a sectional view showing a structure of a polarization transfer device according to a sixth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 10  is a sectional view showing a structure of a polarization transfer device according to a ninth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 11  is a sectional view showing a structure of a polarization transfer device according to an eleventh embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals; 
       FIG. 12  is a diagram showing a relationship among potentials of signals for use to control the polarization transfer device according to the present invention; 
     FIGS.  13 A 1 ,  13 B 1  and  13 C 1  are first state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of a first example; 
     FIGS.  14 D 1 ,  14 E 1  and  14 F 1  are second state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of the first example; 
     FIGS.  15 G 1 ,  15 H 1  and  15 I 1  are first state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of a second example; 
     FIGS.  16 J 1 ,  16 K 1  and  16 L 1  are second state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of the second example; 
     FIGS.  17 A 2 ,  17 B 2  and  17 C 2  are first state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of a seventh example; 
     FIGS.  18 D 2 ,  18 E 2  and  18 F 2  are second state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of the seventh example; 
     FIGS.  19 G 2 ,  19 H 2  and  19 I 2  are first state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of an eighth example; 
     FIGS.  20 J 2 ,  20 K 2  and  20 L 2  are second state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of the eighth example; 
     FIGS.  21 A 3 ,  21 B 3  and  21 C 3  are first state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of a third example; 
     FIGS.  22 D 3 ,  22 E 3  and  22 F 3  are second state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of the third example; 
     FIGS.  23 A 4 ,  23 B 4  and  23 C 4  are first state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of a fourth example; 
     FIGS.  24 D 4 ,  24 E 4  and  24 F 4  are second state diagrams of polarized signals when the polarization transfer device according to the present invention is operated using control signals of the fourth example; 
       FIG. 25  is a diagram showing signal waveforms of a first example used to control the polarization transfer device according to the present invention; 
       FIG. 26  is a diagram showing signal waveforms of a ninth example used to control the polarization transfer device according to the present invention; 
       FIG. 27  is a diagram showing signal waveforms of a tenth example used to control the polarization transfer device according to the present invention; 
       FIG. 28  is a diagram showing signal waveforms of a second example used to control the polarization transfer device according to the present invention; 
       FIG. 29  is a diagram showing signal waveforms of a seventh example used to control the polarization transfer device according to the present invention; 
       FIG. 30  is a diagram showing signal waveforms of an eighth example used to control the polarization transfer device according to the present invention; 
       FIG. 31  is a diagram showing signal waveforms of a third example used to control the polarization transfer device according to the present invention; 
       FIG. 32  is a diagram showing signal waveforms of a fourth example used to control the polarization transfer device according to the present invention; 
       FIG. 33  is a diagram showing signal waveforms of a fifth example used to control the polarization transfer device according to the present invention; 
       FIG. 34  is a diagram showing signal waveforms of a sixth example used to control the polarization transfer device according to the present invention; 
       FIG. 35  is a diagram showing signal waveforms of an eleventh example used to control the polarization transfer device according to the present invention; 
       FIG. 36  is a diagram showing signal waveforms of a twelfth example used to control the polarization transfer device according to the present invention; 
       FIG. 37  is a diagram showing signal waveforms of a thirteenth example used to control the polarization transfer device according to the present invention; 
       FIG. 38  is a diagram showing signal waveforms of a fourteenth example used to control the polarization transfer device according to the present invention; 
       FIG. 39  is a state diagram showing an example of polarization of a ferroelectric material used in the present invention and a conventional example; 
       FIGS. 40A and 40B  are state diagrams showing another example of polarization of a ferroelectric material used in the present invention and a conventional example; 
       FIGS. 41C and 41D  are state diagrams showing an example of polarization of a ferroelectric material in a structure of the polarization transfer device according to the present invention; 
       FIG. 42  is a characteristic curve showing a relationship between applied voltage and polarized charge of a ferroelectric capacitor used in the present invention and a conventional example; 
       FIG. 43  is a sectional view showing a structure of a ferroelectric capacitor used in the present invention and a conventional example; 
       FIG. 44  is a circuit block diagram of a memory cell used for a conventional ferroelectric memory; 
       FIG. 45  is a sectional view showing a structure of a field effect transistor used for a conventional ferroelectric memory, with a ferroelectric thin film formed in the gate; and 
       FIG. 46  is a circuit block diagram of a memory cell array in a conventional ferroelectric memory device using field effect transistors with a ferroelectric thin film formed in the gate. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Before describing the embodiments of the present invention, physical phenomena related to ferroelectric polarization relevant to the present invention will be described to make it easier to understand the constitution of the present invention. 
   About Surface Potential and Polarization Movement 
     FIG. 39  shows an exemplary state of polarization of ferroelectric material. In  FIG. 39 , reference numerals  3901  and  3902  denote the left and right halves of a ferroelectric thin film. The left half  3901  is polarized with the lower part being positive and the upper part being negative. The right half  3902  is polarized with the lower part being negative and the upper part being positive. In this case, if the ferroelectric material has good crystallinity and good characteristics, even though the left half  3901  and right half  3902  are polarized in the reverse direction, they maintain the direction and magnitude of polarization separately. 
     FIGS. 40A and 40B  show a structure in which a ferroelectric thin film  4021  is sandwiched between lower electrode  4023  and upper electrode  4024  in the left part, and between lower electrode  4023  and upper electrode  4025  in the right part, where the lower electrode  4023  is common to the left and right parts. Incidentally, the lower electrode  4023  is at ground potential. On the other hand, a potential is applied to the upper electrode  4024  via a terminal  4026 , and to the upper electrode  4025  via a terminal  4027 . Referring to  FIGS. 40A and 40B , a negative potential is applied to the right upper electrode  4025  to polarize the ferroelectric thin film directly underneath with the upper part being positive and the lower part being negative while allowing potential to discharge from the terminal  4027  and upper electrode  4025 . Next, in  FIG. 40A , a negative potential is applied to the left upper electrode  4024  to polarize the ferroelectric thin film directly underneath the upper electrode  4024  with the upper part being positive and the lower part being negative. In  FIG. 40B , a positive potential is applied to the left upper electrode  4024  to polarize the ferroelectric thin film directly underneath the upper electrode  4024  with the upper part being negative and the lower part being positive. When the state of polarization of the ferroelectric thin film directly underneath the right upper electrode  4025  is checked via the terminal  4027 , the state of the polarization of the ferroelectric thin film directly underneath the upper electrode  4025  remains the same as when a potential is applied first, i.e., the ferroelectric thin film directly underneath the right upper electrode  4025  is polarized with the upper part being positive and the lower part being negative both in  FIGS. 40A and 40B . In other words, although the left and right parts of the ferroelectric material are polarized reversely, the polarization domain wall is retained and they remain separated from each other without interference both in the example of  FIG. 39  and example of  FIGS. 40A and 40B . The above is a well-known phenomenon of polarization of typical ferroelectric thin film. 
   However, under other conditions, there are cases in which a phenomenon is sometimes observed where the above polarization domain wall is not retained. 
   An example is shown in  FIGS. 41C and 41D . The structure shown in  FIGS. 41C and 41D  differs from the structure shown in  FIGS. 40A and 40B  in that a paraelectric insulating layer  4122  is provided between a ferroelectric thin film  4121  and upper electrodes  4124  and  4125 . In this case, a negative potential is applied to the left upper electrode  4124  and right upper electrode  4125  to polarize the ferroelectric thin film directly underneath the upper electrodes  4124  and  4125  with the upper part being positive and the lower part being negative. Then, the upper electrode  4125  and a terminal  4137  are allowed to discharge potential. This state is shown in  FIG. 41D . 
   Next, a positive potential is applied to the left upper electrode  4124  via a terminal  4126 . This polarizes the ferroelectric thin film directly underneath the upper electrode  4124  with the upper part being negative and the lower part being positive. That is, the direction of polarization is reversed along with the positive/negative reversal of the applied voltage. At this time, if the state of polarization of the ferroelectric thin film directly underneath the right upper electrode  4135  is checked via the terminal  4127 , the polarization may be reversed as shown in  FIG. 41C  from its original state shown in  FIG. 40A . The polarization is observed to change more greatly at least in polarization amount than the original state (shown in  FIG. 40A ) in which the upper part is positive and the lower part is negative. The state change and its changing amount depend heavily on the material and thickness of the paraelectric insulating layer as well as on the distance between the electrodes  4124  and  4125 , etc. Presumably, this is because a state of induced charge is changed by the provision of the paraelectric insulating layer, causing changes to the stable state of the potential in the upper part of the ferroelectric thin film. That is, depending on the structure and potential of the upper part of the ferroelectric thin film, it is suggested that the polarization domain wall of the ferroelectric thin film directly underneath can become unstable, causing the polarization to move in the ferroelectric thin film or disappear. 
   In this way, it has been found experimentally that the state of polarization of ferroelectric thin film will change with the material and potential of the upper part of the ferroelectric thin film. The present invention makes use of the above phenomenon aggressively and arbitrarily. Embodiments will be described below. 
   First Embodiment of Device Structure 
     FIG. 1  is a sectional view showing a structure of a polarization transfer device according to a first embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   In  FIG. 1 , the area surrounded by a broken line  110  shows a sectional structure of the polarization transfer device. Reference numeral  111  denotes a ferroelectric thin film made of PZTN;  112  denotes a paraelectric insulating layer made of NiO (nickel oxide);  113 ,  114 ,  115 ,  116 , and  117  denote lower electrodes made of Pt (platinum); and  123 ,  124 ,  125 ,  126 , and  127  denote upper electrodes made of Pt (platinum). Incidentally, although it is assumed here that the ferroelectric thin film  111  is made of PZTN, it may be made of well-known PZT or SBT, where PZT is a general term for Pb(Zr, Ti)O 3 , PZTN is a general term for substances obtained by substituting part of Ti in PZT with Nb, and SBT is general term for SrBi 2 Ta 2 O 9  or substances similar in composition. Also, although it has been stated that the upper electrodes are made of Pt (platinum) as an example, they may be made of another metal such as Ta (tantalum) or Ti (titanium) or metal oxide such as IrO 2  (iridium oxide) or RuO 2  (rubidium oxide) as long as characteristics of the material including reliability are ensured. 
   The ferroelectric thin film  111  and paraelectric insulating layer  112  sandwiched between the lower electrode (first gate electrode)  113  and upper electrode (second gate electrode)  123  compose a first polarization switch, which is surrounded by a chain line  141  in  FIG. 1 . Also, the ferroelectric thin film  111  and paraelectric insulating layer  112  sandwiched between the lower electrode  114  and upper electrode  124  compose a second polarization switch while the ferroelectric thin film  111  and paraelectric insulating layer  112  sandwiched between the lower electrode  115  and upper electrode  125  compose a third polarization switch. 
   On the other hand, the ferroelectric thin film  111  and paraelectric insulating layer  112  sandwiched between the lower electrode  116  and upper electrode  126  compose a first polarization accumulator while the ferroelectric thin film  111  and paraelectric insulating layer  112  sandwiched between the lower electrode  117  and upper electrode  127  compose a second polarization accumulator, which is surrounded by a chain line  145  in  FIG. 1 . 
   The respective lower electrodes  113 ,  114 , and  115  of the first polarization switch, second polarization switch, and third polarization switch are connected to ground potential  131 . The upper electrode  124  of the second polarization switch is connected to a first control signal line  132  for Φ 1 . The respective upper electrodes  123  and  125  of the first polarization switch and third polarization switch are connected to a second control signal line  133  for Φ 2 . 
   The upper electrode  126  of the first polarization accumulator is connected via a terminal  135  to a fourth control signal line for Φ 4 . The lower electrode  116  of the first polarization accumulator is connected via a terminal  134  to a sixth control signal line for Φ 6 . The upper electrode  127  of the second polarization accumulator is connected via a terminal  137  to a third control signal line for Φ 3 . The lower electrode  117  of the second polarization accumulator is connected via a terminal  136  to a fifth control signal line for Φ 5 . 
   With the above configuration, polarization which reflects signals is accumulated and transferred in the ferroelectric thin film, but operation and action vary depending on a combination of signal waveforms of Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  applied to the control signal lines. Examples of the control method will be shown below. 
   First Example of Control Signals 
     FIG. 25  is a diagram showing a first example of signal waveforms applied to the polarization transfer device shown in  FIG. 1  via the control signal lines. In  FIG. 25 , Φ 1  is applied to the upper electrode  124  of the second polarization switch via the control signal line  132  shown in  FIG. 1  while Φ 2  is applied to the respective upper electrodes  123  and  125  of the first polarization switch and third polarization switch via the control signal line  133  shown in  FIG. 1 . Incidentally, the potentials of both Φ 1  and Φ 2  vary between 0 and −V C . 
   Also, in  FIG. 25 , Φ 3  is applied to the upper electrode  127  of the second polarization accumulator shown in  FIG. 1 , Φ 4  is applied to the upper electrode  126  of the first polarization accumulator, Φ 5  is applied to the lower electrode  117  of the second polarization accumulator, and Φ 6  is applied to the lower electrode  116  of the first polarization accumulator. Incidentally, the potentials of all Φ 3 , Φ 4 , Φ 5 , and Φ 6  vary among V B , 0, and −V B . 
   None of V C , −V C , V B , −V B , and 2V B  is higher than the coercive voltage of the ferroelectric thin film  111  in  FIG. 1 . Also, they are set lower than the applied voltage to avoid irreversible impacts on polarized signals to be transferred. Incidentally, the coercive voltage of the ferroelectric thin film is the threshold voltage of positive/negative reversal of polarization charge in  FIG. 42 . 
   In  FIG. 25 , the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  are applied in sync with a basic clock. In an (A 1 ) interval, they are set at −V C , −V C , 0, 0, 0, and 0, respectively. In a (B 1 ) interval, they are set at 0, −V C , 0, 0, 0, 0, respectively. In a (C 1 ) interval, they are set at 0, −V C , 0, 0, 0, 0, respectively. In a (D 1 ) interval, they are set at 0, −V C , V B , −V B , −V B , and V B , respectively. In an (E 1 ) interval, they are set at −V C , −V C , V B , −V B , −V B , and V B , respectively. In an (F 1 ) interval, they are set at −V C , −V C , 0, 0, 0, and 0, respectively. The control voltages and states of polarization in the intervals (A 1 ) to (F 1 ) are shown in FIGS.  13 A 1 ,  13 B 1 ,  13 C 1 ,  14 D 1 ,  14 E 1 , and  14 F 1 , respectively. 
   Now, the states of the polarization transfer device when the control signals are applied in the (A 1 ) interval in  FIG. 25  will be described with reference to FIG.  13 A 1 . 
   In FIG.  13 A 1 , a polarized signal is accumulated in the ferroelectric thin film of the first polarization accumulator, resulting in a polarization with the upper part being negative and the lower part being positive. There is no polarization corresponding to the signal in the ferroelectric thin film of the second polarization accumulator. A potential of −V C  is applied to the upper electrodes of the second polarization switch controlled by Φ 1  and the first and third polarization switches controlled by Φ 2 , causing the ferroelectric thin film directly underneath the first to third polarization switches to be polarized with the upper part being positive and the lower part being negative. Thus, the polarized signal of the first polarization accumulator is separated from the second polarization accumulator by a polarization domain wall of reverse polarity provided by the second polarization switch, causing the polarized signal to be accumulated in the first polarization accumulator and stored in isolation. 
   Next, in the (B 1 ) interval in  FIG. 25 , the potential of Φ 1  is set to 0. Consequently, the polarization domain wall directly underneath the second polarization switch disappears as shown in FIG.  13 B 1 , allowing the polarization corresponding to the signal to move. 
   Next, in the (C 1 ) interval in  FIG. 25 , if the control signal is kept in the state in which it was in the (B 1 ) interval, the polarized signal in the first polarization accumulator becomes able to move through the second polarization switch as shown in FIG.  13 C 1 . Consequently, polarization corresponding to the signal comes into existence both in the first polarization accumulator and second polarization accumulator. 
   Furthermore, in the (D 1 ) interval in  FIG. 25 , a potential of V B  is applied to Φ 3  and Φ 6  while −V B  is applied to Φ 4  and Φ 5 . Consequently, as shown in FIG.  14 D 1 , the upper electrode of the second polarization accumulator changes to V B , attracting the negative charge of signal polarization in the upper part of the ferroelectric thin film while the lower electrode of the second polarization accumulator changes to −V B , attracting the positive charge of the signal polarization in the lower part of the ferroelectric thin film. On the other hand, the upper electrode of the first polarization accumulator changes to −V B , repelling the negative charge of the signal polarization in the upper part of the ferroelectric thin film while the lower electrode of the first polarization accumulator changes to V B , repelling the positive charge of the signal polarization in the lower part of the ferroelectric thin film. Consequently, the signal polarization with the upper part of the ferroelectric thin film negatively charged and the lower part of the ferroelectric thin film positively charged moves from the first polarization accumulator to the second polarization accumulator. 
   Next, in the (E 1 ) interval in  FIG. 25 , a potential of −V C  is applied to Φ 1 . Consequently, as shown in FIG.  14 E 1 , the upper electrode of the second polarization accumulator changes to −V C , causing the movement of the signal polarization through the second polarization switch to stop. 
   Next, in the (F 1 ) interval in  FIG. 25 , the potentials of Φ 3 , Φ 4 , Φ 5 , and Φ 6  are all returned to 0. The potentials of Φ 1  and Φ 2  remain at −V C . Consequently, as shown in FIG.  14 F 1 , the signal polarization is accumulated in the second polarization accumulator. A little polarization component equivalent to a bias caused when a voltage of V B  or −V B  is applied remains in the first polarization accumulator. Incidentally, these polarizations are residual because a 0 voltage is applied to the upper and lower electrodes of the first and second polarization accumulators. Since a potential of −V C  is applied to the upper electrodes of the first, second, and third polarization switches, the first and second polarization accumulators are separated by the first, second, and third polarization switches. 
   When FIGS.  14 F 1  and  13 A 1  are compared, signal polarization which reflects the signal is moving from the first polarization accumulator to the second polarization accumulator. Thus, it can be seen that in the polarization transfer device shown in  FIG. 1 , when the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  shown in  FIG. 25  are applied to respective terminals, the signal polarization moves from the first polarization accumulator to the second polarization accumulator, that is, from left to right. 
   Second Example of Control Signals 
     FIG. 28  is a diagram showing a second example of signal waveforms applied to the polarization transfer device shown in  FIG. 1  via the control signal lines. 
   In  FIG. 28 , the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  are applied in sync with a basic clock. In a (G 1 ) interval, they are set at −V C , −V C , 0, 0, 0, and 0, respectively. In an (H 1 ) interval, they are set at 0, −V C , 0, 0, 0, 0, respectively. In an (I 1 ) interval, they are set at 0, −V C , 0, 0, 0, 0, respectively. In a (J 1 ) interval, they are set at 0, −V C , −V B , V B , V B , and −V B , respectively. In a (K 1 ) interval, they are set at −V C , −V C , −V B , V B , V B , and −V B , respectively. In an (L 1 ) interval, they are set at −V C , −V C , 0, 0, 0, and 0, respectively. 
   The control voltages and states of polarization in the intervals (G 1 ) to (L 1 ) are shown in FIGS.  15 G 1 ,  15 H 1 ,  15 I 1 ,  16 J 1 ,  16 K 1 , and  16 L 1 , respectively. 
   Now, the states of the polarization transfer device when the control signals are applied in the (G 1 ) interval in  FIG. 28  will be described with reference to FIG.  15 G 1 . 
   In FIG.  15 G 1 , a polarized signal is accumulated in the ferroelectric thin film of the second polarization accumulator, resulting in a polarization with the upper part being negative and the lower part being positive. There is no polarization corresponding to the signal in the ferroelectric thin film of the first polarization accumulator. A potential of −V C  is applied to the upper electrodes of the second polarization switch controlled by Φ 1  and the first and third polarization switches controlled by Φ 2 , causing the ferroelectric thin film directly underneath the first to third polarization switches to be polarized with the upper part being positive and the lower part being negative. Thus, the polarized signal of the second polarization accumulator is separated from the first polarization accumulator by a polarization domain wall of reverse polarity provided by the second polarization switch, causing the polarized signal to be accumulated in the second polarization accumulator and stored in isolation. 
   Next, in the (H 1 ) interval in  FIG. 28 , the potential of Φ 1  is set to 0. Consequently, the polarization domain wall directly underneath the second polarization switch disappears as shown in FIG.  15 H 1 , allowing the polarization corresponding to the signal to move. 
   Next, in the (I 1 ) interval in  FIG. 28 , if the control signal is kept in the state in which it was in the (H 1 ) interval, the polarized signal in the second polarization accumulator becomes able to move through the second polarization switch as shown in FIG.  15 I 1 . Consequently, polarization corresponding to the signal comes into existence both in the first polarization accumulator and second polarization accumulator. 
   Furthermore, in the (J 1 ) interval in  FIG. 28 , a potential of −V B  is applied to Φ 3  and Φ 6  while V B  is applied to Φ 4  and Φ 5 . Consequently, as shown in FIG.  16 J 1 , the upper electrode of the first polarization accumulator changes to V B , attracting the negative charge of signal polarization in the upper part of the ferroelectric thin film while the lower electrode of the first polarization accumulator changes to −V B , attracting the positive charge of the signal polarization in the lower part of the ferroelectric thin film. On the other hand, the upper electrode of the second polarization accumulator changes to −V B , repelling the negative charge of the signal polarization in the upper part of the ferroelectric thin film while the lower electrode of the second polarization accumulator changes to V B , repelling the positive charge of the signal polarization in the lower part of the ferroelectric thin film. Consequently, the signal polarization with the upper part of the ferroelectric thin film negatively charged and the lower part of the ferroelectric thin film positively charged moves from the second polarization accumulator to the first polarization accumulator. 
   Next, in the (K 1 ) interval in  FIG. 28 , a potential of −V C  is applied to Φ 1 . Consequently, as shown in FIG.  16 K 1 , the upper electrode of the second polarization switch changes to −V C , causing the movement of the signal polarization through the second polarization switch to stop. 
   Next, in the (L 1 ) interval in  FIG. 28 , the potentials of Φ 3 , Φ 4 , Φ 5 , and Φ 6  are all returned to 0. The potentials of Φ 1  and Φ 2  remain at −V C . Consequently, as shown in FIG.  16 L 1 , the signal polarization is accumulated in the first polarization accumulator. A little polarization component equivalent to a bias caused when a voltage of V B  or −V B  is applied remains in the second polarization accumulator. Incidentally, these polarizations are residual because a 0 voltage is applied to the upper and lower electrodes of the first and second polarization accumulators. Since a potential of −V C  is applied to the upper electrodes of the first, second, and third polarization switches, the first and second polarization accumulators are separated by the first, second, and third polarization switches. 
   When FIGS.  16 L 1  and  15 G 1  are compared, signal polarization which reflects the signal is moving from the second polarization accumulator to the first polarization accumulator. Thus, it can be seen that in the polarization transfer device shown in  FIG. 1 , when the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  shown in  FIG. 28  are applied to respective terminals, the signal polarization moves from the second polarization accumulator to the first polarization accumulator, that is, from right to left. 
   Incidentally, when the first example of the control signals in  FIG. 25  and second example of the control signals in  FIG. 28  are compared, the first example of the control signals is a combination of control signal waveforms which moves signal polarization from left to right and the second example of the control signals is a combination of control signal waveforms which moves signal polarization from right to left. The waveform charts in  FIGS. 25 and 28  differ from each other in intervals (D 1 ) to (E 1 ) and intervals (J 1 ) to (K 1 ) of Φ 3 , Φ 4 , Φ 5 , and Φ 6 . In particular, signal polarization moves most actively in the intervals (D 1 ) and (J 1 ). So in FIG.  14 D 1  which corresponds to the (D 1 ) interval in  FIG. 25 , voltages are applied to the upper and lower electrodes of the first and second polarization accumulators so as to form such electric fields between the upper electrodes as well as between the lower electrodes that will move the signal polarization from the first polarization accumulator to the second polarization accumulator. 
   On the other hand, in FIG.  16 J 1  which corresponds to the (J 1 ) interval in  FIG. 28 , voltages are applied to the upper and lower electrodes of the second and first polarization accumulators so as to form such electric fields between the upper electrodes as well as between the lower electrodes that will move the signal polarization from the second polarization accumulator to the first polarization accumulator. 
   Thus, it can be seen that in the intervals in which the signal polarization moves most actively, the signal polarization can be moved either leftward or rightward depending on how electric fields are formed by the application of voltages to the upper and lower electrodes of the first and second polarization accumulators. 
   Third Example of Control Signals 
     FIG. 31  is a diagram showing a third example of signal waveforms applied to the polarization transfer device shown in  FIG. 1  via the control signal lines. 
   Signal waveforms of Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  are shown in intervals (A 3 ), (B 3 ), (C 3 ), (D 3 ), (E 3 ), and (F 3 ) in  FIG. 31  and states of the polarization transfer device in  FIG. 1  in the intervals (A 3 ) to (F 3 ) are shown in FIGS.  21 A 3 ,  21 B 3 ,  21 C 3 ,  22 D 3 ,  22 E 3 , and  22 F 3 , respectively. 
     FIG. 31  differs from  FIG. 25  (the first example of control signals) in Φ 4  and Φ 6 . Whereas the potentials of Φ 4  and Φ 6  change to −V B  and V B  respectively in the intervals (D 1 ) and (E 1 ) in  FIG. 25 , the potentials remain at 0 in the corresponding intervals (D 3 ) and (E 3 ) in  FIG. 31 . This state has significance especially in FIG.  22 D 3 . Even if the potentials of both Φ 4  and Φ 6  in FIG.  22 D 3  are 0, since the potential of Φ 3  is V B  and the potential of Φ 5  is −V B , there is a force or electric field which attracts signal polarization from the first polarization accumulator to the second polarization accumulator, moving the signal polarization from left to right. Although the force which moves the signal polarization is weaker, if that is all right, it is sometimes useful to select the control signal waveforms of  FIG. 31  to reduce power consumption. 
   Fourth Example of Control Signals 
     FIG. 32  is a diagram showing a fourth example of signal waveforms applied to the polarization transfer device shown in  FIG. 1  via the control signal lines. 
   Signal waveforms of Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  are shown in intervals (A 4 ), (B 4 ), (C 4 ), (D 4 ), (E 4 ), and (F 4 ) in  FIG. 32  and states of the polarization transfer device in  FIG. 1  in the intervals (A 4 ) to (F 4 ) are shown in FIGS.  23 A 4 ,  23 B 4 ,  23 C 4 ,  24 D 4 ,  24 E 4 , and  24 F 4 , respectively. 
     FIG. 32  differs from  FIG. 25  (the first example of control signals) in Φ 3  and Φ 5 . Whereas the potentials of Φ 3  and Φ 5  change to V B  and −V B  respectively in the intervals (D 1 ) and (E 1 ) in  FIG. 25 , the potentials remain at 0 in the corresponding intervals (D 4 ) and (E 4 ) in  FIG. 32 . This state has significance especially in FIG.  24 D 4 . Even if the potentials of both Φ 3  and Φ 5  in FIG.  24 D 4  are 0, since the potential of Φ 4  is −V B  and the potential of Φ 6  is V B , there is a repellent force or electric field which pushes out signal polarization from the first polarization accumulator to the second polarization accumulator, moving the signal polarization from left to right. Although the force which moves the signal polarization is weaker, if that is all right, it is sometimes useful to select the control signal waveforms of  FIG. 32  to reduce power consumption. 
   Second Embodiment of Device Structure 
     FIG. 6  is a sectional view showing a structure of a polarization transfer device according to a second embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   The polarization transfer device in  FIG. 6  is basically a connected series of a plurality of the device structures according to the first embodiment in  FIG. 1 . In  FIG. 6 , the area surrounded by a broken line  601  shows a constitutional unit which corresponds to the polarization transfer device in  FIG. 1 . However, the first and third polarization switches in  FIG. 1  can be shared when connected as shown in  FIG. 6 , which allows adjacent switches to be shared, and thus the first and third polarization switches in  FIG. 6  are shown as being shared. In  FIG. 6 , reference numeral  602  denotes an input terminal which accepts an input signal as a voltage. The polarization transfer device in  FIG. 6  uses non-volatile polarization of a ferroelectric thin film as a signal, but its input section handles signals in terms of voltage. When a positive voltage is applied to the input terminal  602 , polarization corresponding to the input voltage occurs in a polarization input section  603 . Subsequently, the polarization is transmitted successively through the linked structure of the polarization transfer device. 
   Incidentally,  FIG. 12  is a diagram showing a relationship among a supply voltage V; an input signal V sig  resulting from the voltage; control potentials 0 and −V C  of the control signals Φ 1  and Φ 2 ; and control potentials V B , 0, and −V B  of the control signals Φ 3 , Φ 4 , Φ 5 , and Φ 6 . 
   Although in  FIG. 1 , the control voltages of the polarization switches are 0 and −V B  potentials, positive potentials such as +V C  in  FIG. 12  may be used if required in order to obtain desired characteristics. 
   In  FIG. 12 , the input signal V sig  is not higher than the supply voltage V in principle. Also, the potentials V B , −V B , −V C , and V C  are lower than the coercive voltage of the ferroelectric thin film and do not exceed the input signal V sig . 
   Fifth Example of Control Signals 
     FIG. 33  is a diagram showing a fifth example of signal waveforms applied to the polarization transfer device shown in  FIG. 6  via the control signal lines. 
   As described above, the polarization transfer device in  FIG. 6  is a form-connected series of a plurality of the device structures according to the first embodiment in  FIG. 1 . Also, each control signal Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , or Φ 6  in  FIG. 33  is a two-connected series of the respective control signal waveforms in  FIG. 25 . 
   Incidentally, although in  FIG. 25 , the potentials of Φ 3  and Φ 6  are 0 and V B  while the potentials of Φ 4  and Φ 5  are 0 and −V B ; the potentials of Φ 3 , Φ 4 , Φ 5 , and Φ 6  in FIG.  33  vary among −V B , 0, and V B . This is because whereas  FIG. 25  shows control signal waveforms produced in  FIG. 1  only during movement from the first polarization accumulator to the second polarization accumulator; with the configuration consisting of a further connected series of the basic structures of the polarization transfer device shown in  FIG. 1 , that is, a relation is established that Φ 3 , Φ 4 , Φ 5 , and Φ 6  change places during transfer from the second polarization accumulator to the third polarization accumulator on the adjacent right. Since the control signal waveform chart in  FIG. 33  is a connected series of the control signal waveform charts in  FIG. 25  as described above, when the polarization transfer device shown in  FIG. 6  is controlled using the control signal waveforms in  FIG. 33 , signal polarization is transmitted successively rightward. Incidentally, timing of application of the input signal in  FIG. 6  is also shown in  FIG. 33 . In  FIG. 33 , if the input signal V sig  is established at a timing other than those which correspond to slant lines of D 1 , D 2 , D 3 , and the like, it can be entered normally. 
   Sixth Example of Control Signals 
     FIG. 34  is a diagram showing a sixth example of signal waveforms applied to the polarization transfer device shown in  FIG. 6  via the control signal lines. 
   As described above, the polarization transfer device in  FIG. 6  is a form-connected series of a plurality of the device structures according to the first embodiment in  FIG. 1 . Also, each control signal Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , or Φ 6  in  FIG. 34  is a time-connected series of the respective control signal waveforms in  FIG. 26 . Thus, it can be seen that the control signal waveforms in  FIG. 34  cause signal polarization to be transferred from right to left on the polarization transfer device in  FIG. 6 . 
   Incidentally, although in  FIG. 26 , the potentials of Φ 3  and Φ 6  are 0 and −V B  while the potentials of Φ 4  and Φ 5  are 0 and V B , the potentials of Φ 3 , Φ 4 , Φ 5 , and Φ 6  in  FIG. 34  vary among −V B , 0, and V B . The reason is almost the same as the one for the connected series of the basic structures of the polarization transfer device according to the fifth example of control signals. Besides, the input signal V sig  shown in  FIG. 33  is not shown in  FIG. 34 . This is because it is assumed that no signal is entered via the input terminal  602  during transfer in reverse from right to left on the polarization transfer device in  FIG. 6 . 
   Third Embodiment of Device Structure 
     FIG. 2  is a sectional view showing a structure of a polarization transfer device according to a third embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   Basically, the device structure in  FIG. 2  is an adapted version of the device structure according to the first embodiment in  FIG. 1 .  FIG. 2  differs from  FIG. 1  in that the respective lower electrodes  113 ,  114 , and  115  of the first, second, and third polarization switches as well as the respective lower electrodes  116  and  117  of the first and second polarization accumulators in  FIG. 1  are replaced by a common electrode  118 . The rest of the structure is the same as in  FIG. 1 . With the structure in  FIG. 2 , since the common electrode  118  is wide and made of platinum (Pt), the ferroelectric thin film  111  placed on it and made of PZTN has an affinity with the crystal axis of the platinum of the lower electrode. This facilitates crystal growth, resulting in highly reliable ferroelectric crystals with excellent electrical characteristics, and thus makes the polarization transfer device a more reliable product with a higher production stability than the first embodiment in  FIG. 1 . 
   Seventh Example of Control Signals 
     FIG. 29  is a diagram showing a seventh example of signal waveforms applied to the polarization transfer device shown in  FIG. 2  via the control signal lines. 
   Signal waveforms of Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  are shown in intervals (A 2 ), (B 2 ), (C 2 ), (D 2 ), (E 2 ), and (F 2 ) in  FIG. 29  and states of the polarization transfer device in  FIG. 2  in the intervals (A 2 ) to (F 2 ) are shown in FIGS.  17 A 2 ,  17 B 2 ,  17 C 2 ,  18 D 2 ,  18 E 2 , and  18 F 2 , respectively. 
     FIG. 29  differs from  FIG. 25  (the first example of control signals) in Φ 5  and Φ 6 . Specifically, the respective lower electrodes  113 ,  114 , and  115  of the first, second, and third polarization switches as well as the respective lower electrodes  116  and  117  of the first and second polarization accumulators in  FIG. 1  are replaced in  FIG. 2  by the common electrode  118 , which is fixed at the ground potential of 0. Consequently, Φ 5  and Φ 6  in  FIG. 29  are always at 0 potential. 
   Thus, whereas the potentials of Φ 5  and Φ 6  change to −V B  and V B  respectively in the intervals (D 1 ) and (E 1 ) in  FIG. 25  (the first example of control signals), the potentials remain at 0 in the corresponding intervals (D 2 ) and (E 2 ) in  FIG. 29 . This state has significance especially in FIG.  18 D 2 . Even if the potentials of both Φ 5  and Φ 6  in FIG.  18 D 2  are 0, since the potential of Φ 4  is −V B  and the potential of Φ 3  is V B , there are both repellent force which pushes out signal polarization and attraction force which pulls out the signal polarization, from the first polarization accumulator to the second polarization accumulator via the upper electrodes, or there are electric fields which function similarly, moving the signal polarization from left to right. 
   Eighth Example of Control Signals 
     FIG. 30  is a diagram showing an eighth example of signal waveforms applied to the polarization transfer device shown in  FIG. 2  via the control signal lines. 
   Signal waveforms of Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  are shown in intervals (G 2 ), (H 2 ), (I 2 ), (J 2 ), (K 2 ), and (L 2 ) in  FIG. 30  and states of the polarization transfer device in  FIG. 2  in the intervals (G 2 ) to (L 2 ) are shown in FIGS.  19 G 2 ,  19 H 2 ,  19 I 2 ,  20 J 2 ,  20 K 2 , and  20 L 2 , respectively. 
     FIG. 30  differs from  FIG. 26  (the second example of control signals) in Φ 5  and Φ 6 . Specifically, the respective lower electrodes  113 ,  114 , and  115  of the first, second, and third polarization switches as well as the respective lower electrodes  116  and  117  of the first and second polarization accumulators in  FIG. 1  are replaced in  FIG. 2  by the common electrode  118 , which is fixed at the ground potential of 0. Consequently, Φ 5  and Φ 6  in  FIG. 30  are always at 0 potential. 
   Thus, whereas the potentials of Φ 5  and Φ 6  change to V B  and −V B  respectively in the intervals (J 1 ) and (K 1 ) in  FIG. 28  (the second example of control signals), the potentials remain at 0 in the corresponding intervals (J 2 ) and (K 2 ) in  FIG. 30 . This state has significance especially in FIG.  20 J 2 . Even if the potentials of both Φ 5  and Φ 6  in FIG.  20 J 2  are 0, since the potential of Φ 3  is −V B  and the potential of Φ 4  is V B , there are both repellent force which pushes out signal polarization and attraction force which pulls out the signal polarization, from the second polarization accumulator to the first polarization accumulator via the upper electrodes, or there are electric fields which function similarly, moving the signal polarization from right to left. 
   Fourth Embodiment of Device Structure 
     FIG. 8  is a sectional view showing a structure of a polarization transfer device according to a fourth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   The polarization transfer device in  FIG. 8  is basically a connected series of a plurality of the device structures according to the third embodiment in  FIG. 2 . In  FIG. 8 , the area surrounded by a broken line  801  shows a constitutional unit which corresponds to the polarization transfer device in  FIG. 2 . However, the first and third polarization switches in  FIG. 2  can be shared when connected as shown in  FIG. 8 , which allows adjacent switches to be shared, and thus the first and third polarization switches in  FIG. 8  are shown as being shared. In  FIG. 8 , reference numeral  802  denotes an input terminal which accepts an input signal as a voltage. The polarization transfer device in  FIG. 8  uses non-volatile polarization of a ferroelectric thin film as a signal, but its input section handles signals in terms of voltage. When a positive voltage is applied to the input terminal  802 , polarization corresponding to the input voltage occurs in a polarization input section  803 . Subsequently, the polarization is transmitted successively through the linked structure of the polarization transfer device. 
   Incidentally, the polarization transfer device according to the fourth embodiment in  FIG. 8  can be viewed as the polarization transfer device according to the second embodiment in  FIG. 6  with a common electrode being used for the lower electrodes of all the polarization switches and polarization accumulators. 
   When the structure shown in  FIG. 8  is compared with the structure shown in  FIG. 6 , since the lower electrode is wide and formed as a common electrode made of contiguous platinum (Pt), the ferroelectric thin film placed on it and made of PZTN has an affinity with the crystal axis of the platinum of the lower electrode. This facilitates crystal growth, resulting in highly reliable ferroelectric crystals with excellent electrical characteristics, and thus makes the polarization transfer device a more reliable product with a higher production stability than the second embodiment in  FIG. 6 . 
   Fifth Embodiment of Device Structure 
     FIG. 3  is a sectional view showing a structure of a polarization transfer device according to a fifth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   Basically, the device structure in  FIG. 3  follows suit with the device structure in  FIG. 2 . It differs in that a paraelectric insulating layer  312  directly underneath the upper electrodes  123 ,  124 , and  125  of the first, second, and third polarization switches is made of a material different from that of the paraelectric insulating layer  112  directly underneath the upper electrodes  126  and  127  of the first and second polarization accumulators. The paraelectric insulating layer  312  is made of a material which has a different relative dielectric constant from the paraelectric insulating layer  112  and has such characteristics that polarization movement in the ferroelectric thin film will occur when the potentials of the upper electrodes  123 ,  124 , and  125  of the first, second, and third polarization switches are +V C , but not when the potentials are 0. Thus, the potentials of the upper electrodes  123 ,  124 , and  125  of the first, second, and third polarization switches are controlled to vary either between −V C  and +V C  or between 0 and +V C . Then, by making full use of the non-volatility feature, polarized signals are stored reliably not only when the polarization transfer device is powered on, but also when it is powered off. 
   The fifth embodiment features almost the same structure, operation, and functionality as the third embodiment in  FIG. 2  except that the paraelectric insulating layer directly underneath the upper electrodes of the polarization switches is made of a different material as described above. 
   Sixth Embodiment of Device Structure 
     FIG. 9  is a sectional view showing a structure of a polarization transfer device according to a sixth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   Basically, the device structure in  FIG. 9  follows suit with the device structure in  FIG. 8 . It differs in that a paraelectric insulating layer  912  directly underneath the upper electrodes of polarization switches is made of a material different from that of the paraelectric insulating layer  112  directly underneath the upper electrodes of polarization accumulators. The paraelectric insulating layer  912  is made of a material which has a different relative dielectric constant from the paraelectric insulating layer  112  and has such characteristics that polarization movement in the ferroelectric thin film will occur when the potentials of the upper electrodes of the polarization switches are +V C , but not when the potentials are 0. Thus, the potentials of the upper electrodes of the polarization switches are controlled to vary either between −V C  and +V C  or between 0 and +V C . Thus, by making full use of the non-volatility feature, polarized signals are stored reliably not only when the polarization transfer device is powered on, but also when it is powered off. 
   Seventh Embodiment of Device Structure 
     FIG. 7  is a sectional view showing a structure of a polarization transfer device according to a seventh embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
     FIG. 7  is an application of the technique used in the fifth and sixth embodiments to the second embodiment in  FIG. 6 , where the technique involves the use of a different material for the paraelectric insulating layer  712  directly underneath the upper electrodes of polarization switches from the material of the paraelectric insulating layer  112  directly underneath the upper electrodes of polarization accumulators. 
   Specifically, in  FIG. 7 , a paraelectric insulating layer  712  directly underneath the upper electrodes of polarization switches is made of a material different from the paraelectric insulating layer  112  directly underneath the upper electrodes of polarization accumulators. The paraelectric insulating layer  712  is made of a material which has a different relative dielectric constant from that of the paraelectric insulating layer  112  and has such characteristics that polarization movement in the ferroelectric thin film will occur when the potentials of the upper electrodes of the polarization switches are +V C , but not when the potentials are 0. Thus, the potentials of the upper electrodes of the polarization switches are controlled to vary either between −V C  and +V C  or between 0 and +V C . Thus, by making full use of the non-volatility feature, polarized signals are stored reliably not only when the polarization transfer device is powered on, but also when it is powered off. 
   Eighth Embodiment of Device Structure 
     FIG. 4  is a sectional view showing a structure of a polarization transfer device according to an eighth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   Basically, the device structure in  FIG. 4  is a high-density version of the device structure according to the third embodiment in  FIG. 2 .  FIG. 4  differs from  FIG. 2  in that respective upper electrodes  423 ,  424 , and  425  of the first, second, and third polarization switches are formed in a different layer by a different manufacturing process from the upper electrodes  126  and  127  of the first and second polarization accumulators. Also, in  FIG. 4 , the upper electrodes  126  and  127  of the first and second polarization accumulators are formed at a shorter distance. Otherwise, the polarization transfer device in  FIG. 4  has almost the same structure and uses the same method of control as the polarization transfer device in  FIG. 2 . 
   In  FIG. 4 , reference numeral  119  denotes an insulating layer made of SiO 2 , NiO, or the like. The respective upper electrodes  423 ,  424 , and  425  of the first, second, and third polarization switches are provided above the upper electrodes  126  and  127  of the first and second polarization accumulators via the insulating layer  119 . Since the upper electrode  424  of the second polarization switch has been moved upward, the respective upper electrodes  126  and  127  of the first and second polarization accumulators are brought closer to each other so that the distance between them will be equal to the metal width of the upper electrode  424  of the second polarization switch. The upper electrodes of the polarization switches control the polarization of the ferroelectric thin film through clearances at the sides of the upper electrodes of the polarization accumulators. In so doing, a little higher control voltage is used as a control voltage than that in  FIG. 2 . Also, in  FIG. 4 , since the respective upper electrodes  423 ,  424 , and  425  of the first, second, and third polarization switches cover the clearances at the sides of the respective upper electrodes  126  and  127  of the first and second polarization accumulators, the states of the paraelectric insulating layer  112  and the ferroelectric thin film  111  can be controlled reliably by control signals using the respective upper electrodes  423 ,  424 , and  425  of the first, second, and third polarization switches as well as the respective upper electrodes  126  and  127  of the first and second polarization accumulators. Also, as described above, since the respective upper electrodes  126  and  127  of the first and second polarization accumulators can be brought closer to each other in the embodiment in  FIG. 4  than in  FIG. 2 , it is possible to increase packing density as well as efficiency of transfer between the first and second polarization accumulators. 
   This makes it possible to provide a polarization transfer device which feature high packing density, high transfer efficiency, and good controllability of polarization movement and polarization retention. 
   Ninth Embodiment of Device Structure 
     FIG. 10  is a sectional view showing a structure of a polarization transfer device according to a ninth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   The polarization transfer device in  FIG. 10  is basically a connected series of a plurality of the device structures according to the eighth embodiment in  FIG. 4 . 
   In  FIG. 10 , the area surrounded by a broken line  1001  shows a constitutional unit which corresponds to the polarization transfer device in  FIG. 4 . However, the first and third polarization switches in  FIG. 4  can be shared when connected as shown in  FIG. 10 , which allows adjacent switches to be shared, and thus the first and third polarization switches in  FIG. 10  are shown as being shared. In  FIG. 10 , reference numeral  1002  denotes an input terminal which accepts an input signal as a voltage. The polarization transfer device in  FIG. 10  uses non-volatile polarization of a ferroelectric thin film as a signal, but its input section handles signals in terms of voltage. When a positive voltage is applied to the input terminal  1002 , polarization corresponding to the input voltage occurs in a polarization input section  1003 . Subsequently, the polarization is transmitted successively through the linked structure of the polarization transfer device. 
   Incidentally, the polarization transfer device according to the ninth embodiment in  FIG. 10  can be viewed as the polarization transfer device according to the fourth embodiment in  FIG. 8  with the upper electrodes of the polarization switches being formed in an upper layer separately from the upper electrodes of the polarization accumulators. 
   When the structure shown in  FIG. 10  is compared with the structure shown in  FIG. 8 , the polarization accumulators are closer to each other, and thus the structure in  FIG. 10  can improve packing density and transfer efficiency. 
   Also, since the upper electrodes of the polarization switches in  FIG. 10  cover the space between the upper electrodes of the polarization accumulators, the structure in  FIG. 10  features better controllability of the polarization switches than does the structure in  FIG. 8 . 
   Tenth Embodiment of Device Structure 
     FIG. 5  is a sectional view showing a structure of a polarization transfer device according to a tenth embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   The structure in  FIG. 5  is the same as the structure according to the eighth embodiment in  FIG. 4  except that vertical relationship are exchanged between the upper electrodes of the polarization switches and upper electrodes of the polarization accumulators. That is, in  FIG. 5 , the upper electrodes  123 ,  124 , and  125  of the first, second, and third polarization switches are mounted directly on the paraelectric insulating layer  112  and the upper electrodes  526  and  527  of the first and second polarization accumulators are placed on the insulating layer  119 . 
   Since the structure in  FIG. 5  differs from the structure in  FIG. 4  only in the vertical relationship between the upper electrodes of the polarization switches and upper electrodes of the polarization accumulators, it inherits high packing density, high transfer efficiency, and good controllability of polarization movement and polarization retention as they are from the polarization transfer device according to the eighth embodiment in  FIG. 4 . Furthermore, since the upper electrodes of the polarization switches are closer to the ferroelectric thin film than in the structure in  FIG. 4 , the structure in  FIG. 5  has a feature much improved in view of controllability of the polarization switches. 
   Eleventh Embodiment of Device Structure 
     FIG. 11  is a sectional view showing a structure of a polarization transfer device according to an eleventh embodiment of the present invention and at the same time a connection diagram showing a relationship with control signals. 
   The polarization transfer device in  FIG. 11  is basically a connected series of a plurality of the device structures according to the tenth embodiment in  FIG. 5 . In  FIG. 11 , the area surrounded by a broken line  1101  shows a constitutional unit which corresponds to the polarization transfer device in  FIG. 5 . However, the first and third polarization switches in  FIG. 5  can be shared when connected as shown in  FIG. 11 , which allows adjacent switches to be shared, and thus the first and third polarization switches in  FIG. 11  are shown as being shared. In  FIG. 11 , reference numeral  1102  denotes an input terminal which accepts an input signal as a voltage. The polarization transfer device in  FIG. 11  uses non-volatile polarization of a ferroelectric thin film as a signal, but its input section handles signals in terms of voltage. When a positive voltage is applied to the input terminal  1102 , polarization corresponding to the input voltage occurs in a polarization input section  1103 . Subsequently, the polarization is transmitted successively through the linked structure of the polarization transfer device. 
   Incidentally, since the polarization transfer device according to the eleventh embodiment in  FIG. 11  can be viewed as the polarization transfer device according to the ninth embodiment in  FIG. 10  with vertical relationship being exchanged between the upper electrodes of the polarization switches and upper electrodes of the polarization accumulators, it inherits high packing density, high transfer efficiency, and good controllability of polarization movement and polarization retention as they are from the polarization transfer device according to the ninth embodiment in  FIG. 10 . Furthermore, since the upper electrodes of the polarization switches are closer to the ferroelectric thin film than in the structure in  FIG. 10 , the structure in  FIG. 11  has a feature much improved in view of controllability of the polarization switches. 
   Ninth Example of Control Signals 
     FIG. 26  is a diagram showing a ninth example of signal waveforms applied to the polarization transfer device according to the fifth, eighth, or tenth embodiment in  FIG. 3 ,  4 , or  5  via the control signal lines. 
   The signal waveforms on the control signal lines in  FIG. 26  differ from those according to the first example of the control signals in  FIG. 25  in that the control signals Φ 1  and Φ 2  for the upper electrodes of the polarization switches are controlled to vary between potentials of 0 and +V C  in  FIG. 26  while they are controlled to vary between potentials of −V C  and 0 in  FIG. 25 . An appropriate range of the control voltage for polarization switches depends on the material and thickness of the ferroelectric thin film or paraelectric insulating layer, but generally the control voltage in  FIG. 26  allows higher retention and non-volatility of polarization than the control voltage in  FIG. 25 . 
   Tenth Example of Control Signals 
     FIG. 27  is a diagram showing a tenth example of signal waveforms applied to the polarization transfer device according to the fifth, eighth, or tenth, embodiment in  FIG. 3 ,  4 , or  5  via the control signal lines. 
   The signal waveforms on the control signal lines in  FIG. 27  differ from those according to the first example of the control signals in  FIG. 25  or ninth example of the control signals in  FIG. 26  in that the control signals Φ 1  and Φ 2  for the upper electrodes of the polarization switches are controlled to vary between potentials of −V C  and +V C  in  FIG. 27  while they are varied between potentials of −V C  and 0 in  FIG. 25  and between potentials of 0 and +V C  in  FIG. 26 . An appropriate range of the control voltage for polarization switches depends on the material and thickness of the ferroelectric thin film or paraelectric insulating layer, but generally the control voltage in  FIG. 27  allows higher retention and non-volatility of polarization than the control voltage in  FIG. 25  or  26 . 
   Eleventh Example of Control Signals 
     FIG. 35  is a diagram showing an eleventh example of signal waveforms applied to the polarization transfer device according to the seventh, sixth, ninth, or eleventh embodiment in  FIG. 7 ,  9 ,  10 , or  11  via the control signal lines. 
   The signal waveforms on the control signal lines in  FIG. 35  differ from those according to the fifth example of the control signals in  FIG. 33  in that the control signals Φ 1  and Φ 2  for the upper electrodes of the polarization switches are controlled to vary between potentials of 0 and +V C  in  FIG. 35  while they are controlled to vary between potentials of −V C  and 0 in  FIG. 33 . An appropriate range of the control voltage for polarization switches depends on the material and thickness of the ferroelectric thin film or paraelectric insulating layer, but generally the control voltage in  FIG. 35  allows higher retention characteristics and non-volatility of polarization than the control voltage in  FIG. 33 . 
   Twelfth Example of Control Signals 
     FIG. 36  is a diagram showing a twelfth example of signal waveforms applied to the polarization transfer device according to the seventh, sixth, ninth, or eleventh embodiment in  FIG. 7 ,  9 ,  10 , or  11  via the control signal lines. 
   The signal waveforms on the control signal lines in  FIG. 36  differ from those according to the sixth example of the control signals in  FIG. 34  in that the control signals Φ 1  and Φ 2  for the upper electrodes of the polarization switches are controlled to vary between potentials of 0 and +V C  in  FIG. 36  while they are controlled to vary between potentials of −V C  and 0 in  FIG. 34 . An appropriate range of the control voltage for polarization switches depends on the material and thickness of the ferroelectric thin film or paraelectric insulating layer, but generally the control voltage in  FIG. 36  allows higher retention and non-volatility of polarization than the control voltage in  FIG. 34 . 
   Thirteenth Example of Control Signals 
     FIG. 37  is a diagram showing a thirteenth example of signal waveforms applied to the polarization transfer device according to the seventh, sixth, ninth, or eleventh embodiment in  FIG. 7 ,  9 ,  10 , or  11  via the control signal lines. 
   The signal waveforms on the control signal lines in  FIG. 37  differ from those according to the fifth example of the control signals in  FIG. 33  or eleventh example of the control signals in  FIG. 35  in that the control signals Φ 1  and Φ 2  for the upper electrodes of the polarization switches are controlled to vary between potentials of −V C  and +V C  in  FIG. 37  while they are varied between potentials of −V C  and 0 in  FIG. 33  and between potentials of 0 and +V C  in  FIG. 35 . An appropriate range of the control voltage for polarization switches depends on the material and thickness of the ferroelectric thin film or paraelectric insulating layer, but generally the control voltage in  FIG. 37  allows higher retention and non-volatility of polarization than the control voltage in  FIG. 33  or  35 . 
   Fourteenth Example of Control Signals 
     FIG. 38  is a diagram showing a fourteenth example of signal waveforms applied to the polarization transfer device according to the seventh, sixth, ninth, or eleventh embodiment in  FIG. 7 ,  9 ,  10 , or  11  via the control signal lines. 
   The signal waveforms on the control signal lines in  FIG. 38  differ from those according to the sixth example of the control signals in  FIG. 34  or twelfth example of the control signals in  FIG. 36  in that the control signals Φ 1  and Φ 2  for the upper electrodes of the polarization switches are controlled to vary between potentials of −V C  and +V C  in  FIG. 38  while they are controlled to vary between potentials of −V C  and 0 in  FIG. 34  and between potentials of 0 and +V C  in  FIG. 36 . An appropriate range of the control voltage for polarization switches depends on the material and thickness of the ferroelectric thin film or paraelectric insulating layer, but generally the control voltage in  FIG. 38  allows higher retention and non-volatility of polarization than the control voltage in  FIG. 34  or  36 . 
   Other Embodiments 
   The present invention is not limited to the embodiments described above, and other embodiments will be listed below. 
   Input signals of positive polarity have been cited above and waveforms of the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  have been presented in combinations suitable for the input signals, but there are also suitable combinations of waveforms of the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  even if input signals are of negative polarity. Waveforms of the control signals Φ 1 , Φ 2 , Φ 3 , Φ 4 , Φ 5 , and Φ 6  can be combined in such a way as to generate an electric field which will move signal polarization leftward or rightward. 
   Although a method which involves applying a fixed 0 potential to the lower electrodes of the polarization switches has been described above, there is also a method which applies positive or negative potentials to the individual lower electrodes to enhance a switching function of the polarization switches. 
   Also, although in the above examples, the control voltages applied to the terminals of the polarization switches are −V C , 0, and +V C  and the control voltages applied to the terminals of the polarization accumulators are −V B , 0, and +V B , the absolute values of the positive and negative potentials may not be equal to each other. 
   Also, although in the above embodiments, both polarization switches and polarization accumulators have upper and lower electrodes, their electrodes may be arranged horizontally rather than vertically. 
   Also, although PZTN, PZT, and SBT have been cited as examples of ferroelectric materials, the present invention may use other ferroelectric materials such as BLT (Bi 4x La x Ti 3 O 12 ), BaTiO 3 , SrTiO 3 , Bi 4 Ti 3 O 12 , and BaBiNb 2 O 9 . There can be an infinite number of materials if the proportions of the constituents are changed. Besides, an upper layer and lower layer of different ferroelectric materials may be laminated. 
   Also, although in the first to seventh embodiments of the device structure in  FIGS. 1 to 11 , the paraelectric insulating layer  112  made of NiO (nickel oxide) is provided between the ferroelectric thin film  111  and upper electrodes ( 123  to  127 ), it may be provided between the ferroelectric thin film  111  and lower electrodes ( 113  to  118 ), provided that such material and manufacturing process that will not hinder crystal growth of the ferroelectric thin film  111  can be selected. This is expected to improve polarization movement and transfer efficiency. 
   Also, although in the first to seventh embodiments of the device structure in  FIGS. 1 to 7 , the paraelectric insulating layer  112  made of NiO (nickel oxide) is provided between the ferroelectric thin film  111  and upper electrodes ( 123  to  127 ), this is not absolutely necessary requirement. The paraelectric insulating layer  112  is provided to remove the polarization domain wall between different polarizations in the ferroelectric thin film  111  or facilitate its movement by means of induced charge or the potential of the upper electrodes. Thus, the polarization domain wall may be removed or moved even without the paraelectric insulating layer  112  if the ferroelectric thin film  111  is made of an appropriate material, is multilayered, or is otherwise constructed ingeniously or an appropriate potential is applied to the upper electrodes. 
   Also, although in  FIGS. 3 ,  7 , and  9 , the paraelectric insulating layer directly underneath the upper electrodes of the polarization switches and paraelectric insulating layer directly underneath the upper electrodes of the polarization accumulators are made of different materials while in  FIGS. 4 ,  5 ,  10 , and  11 , the upper electrodes of the polarization switches and the upper electrodes of the polarization accumulators are constructed in different layers, the two methods may be used in combination. 
   Also, although a ferroelectric memory has been cited as an application example of the polarization transfer device according to the present invention, the polarization transfer device, which is a non-volatile signal storage/transfer device in principle, is expected to find many other applications as a non-volatile delay element. 
   Also, although ferroelectric memories use digital signals of 1 and 0 in principle, the polarization transfer device according to the present invention can also handle analog signals or multilevel signals.