# Patent

## Title
Semiconductor device and operation method for same

## Abstract

A semiconductor device, includes first, second, and third switching elements. The third switching element comprises first and second terminals. Each of the first and second switching elements comprise a unified ion conductor, a first electrode disposed to contact the ion conductor and supply metal ions thereto, and a second electrode disposed to contact the ion conductor and is less susceptible to ionization than the first electrode. The first electrodes of the first switching element and the second switching element are electrically connected. The first terminal of the third switching element is electrically connected to only the first electrodes which are electrically connected, or the second electrode of the first switching element and the second electrode of the second switching element are electrically connected. The first terminal of the third switching element is electrically connected to only the second electrodes which are electrically connected.

## Background
RELATED APPLICATIONS
This application is a Continuation application of U.S. patent application Ser. No. 13/704,225, filed on Dec. 13, 2012, which claims priority as a 371 Application of PCT/JP2011/063756, filed on Jun. 9, 2011, which further claims priority from JPA No. 2010-136988, filed on Jun. 16, 2010, incorporated herein by reference.


TECHNICAL FIELD
The present invention relates to a semiconductor device and an operation method for the same, and particularly relates to a semiconductor device and an operation method for the same which use a variable resistance type nonvolatile element.
BACKGROUND ART
The semiconductor device, especially the silicon device has been progressed in the large scale integration and the low power consumption through applying the miniaturization (scaling rule: Moore's rule), and has been developed in a pace of four times progress every three years. It is required to improve device performance through applying an approach different from the conventional scaling rule, because the gate length of MOSFET (Metal Oxide Semiconductor Field Effect Transistor) nowadays has become shorter than 20 nm, a cost of the lithography process rises suddenly, and there exists physical limit to the device size. The steep rise in the cost of the lithography process is, for example, a steep rise in the prices of an apparatus and a mask set. The physical limit to the device size is, for example, a limit to the operation and a limit due to the manufacturing deviation.
In order to improve the limit, in recent years, a programmable logic device which is rewritable and is called FPGA has been developed as an intermediate device between the gate array and the standard cell. FPGA makes it possible that, after a chip is manufactured, a customer configures a circuit through carrying out an electrical wiring on the chip arbitrarily. It is expected that the power consumption may be further lowered through using a variable resistance element inside a multi-layered wiring layer of FPGA. As the variable resistance element, there are ReRAM (Resistance Random Access Memory) using the transition metal oxide, NanoBridge (registered trademark by NEC Corporation) using the ion conductor and the like. Patent literature 1 and non-patent literature 1 disclose a variable resistance element using the mobility of the metal ion and the electrochemical reaction in the solid in which the metal ion can move freely by applying an electric field or the like. The solid, in which the ion can move freely by applying the electric field, is an ion conductor. The variable resistance element, which is disclosed in the patent literature 1 and the non-patent literature 1, includes an ion conducting layer, and a first electrode and a second electrode which are disposed on the opposite surfaces contacting with the ion conducting layer. The metal ion is supplied from the first electrode to the ion conducting layer, and the metal ion is not supplied from the second electrode. According to the variable resistance element which is disclosed in the patent literature 1 and the non-patent literature 1, a value of the electrical resistance is made to vary through changing polarity of an applied voltage and a state of conduction between two electrodes are controlled. Moreover, the patent literature 1 and the non-patent literature 1 disclose a crossbar switch which uses the variable resistance element in ULSI (Ultra-Large Scale Integration).
CITATION LIST
Patent Literature 1: Japanese Patent Application Laid-Open No. 2005-101535
Non-patent Literature 1: Shunichi Kaeriyama et al., “A Nonvolatile Programmable Solid-Electrolyte Nanometer Switch”, IEEE Journal of Solid-State Circuits, Vol. 40, No. 1, pp. 168-176, Jan. 2005.
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
However, the variable resistance element, which is described in the patent literature 1 and the non-patent literature 1, has the following problem. That is, in the case that the two terminals type variable resistance element, which is described in the patent literature 1 and the non-patent literature 1, is applied to the crossbar switch which is used on a signal line of ULSI, the problem arises that an erroneous writing is caused to the variable resistance element with a state of high electrical resistance by an amplitude of a signal which propagates through the adjacent switch. That is, an off disturbing problem arises. In particular, in the case that a programming voltage of the variable resistance element becomes lowered in order to make the programming voltage approach to an operating voltage of the logic LSI, the above-mentioned off disturbing problem becomes more remarkable. As a result, there is a problem that lowering the programming voltage improving the resistance to the off disturbing problem are not compatible each other. In other words, there is a problem that lowering the programming voltage and achieving high reliability are not compatible each other.
The object of the present invention is, solving the problem mentioned above, to provide a semiconductor device and an operation method for the same of which are able to achieve the high reliability and to lower the voltage.
Means for Solving Problem
In order to solve the problem mentioned above, a semiconductor device according to the present invention includes: a cell which includes a first switching element, a second switching element, and at least one third switching element; wherein the third switching element includes a first terminal and a second terminal, each of the first switching element and the second switching element includes an ion conductor, a first electrode which is disposed so as to have contact with the ion conductor and supplies metal ions to the ion conductor, and a second electrode which is disposed so as to have contact with the ion conductor and is less susceptible to ionization than the first electrode; and wherein
(a) in the cell, the first electrode of the first switching element, the first electrode of the second switching element and the first terminal of the third switching element are electrically connected each other, or
(b) in the cell, the second electrode of the first switching element, the second electrode of the second switching element, and the first terminal of the third switching element are electrically connected each other.
Moreover, an operation method for a semiconductor device which includes a first switching element, a second switching element, and at least one third switching element; wherein the third switching element includes a first terminal and a second terminal, each of the first switching element and the second switching element includes an ion conductor, a first electrode which is disposed so as to have contact with the ion conductor and supplies metal ions to the ion conductor, and a second electrode which is disposed so as to have contact with the ion conductor and is less susceptible to ionization than the first electrode;
(a) the first electrode of the first switching element and the first electrode of the second switching element are electrically connected each other, and a first terminal of the third switching element is electrically connected to only the first electrodes which are connected each other or
(b) the second electrode of the first switching element and the second electrode of the second switching element are electrically connected each other, and a first terminal of the third switching element is electrically connected to only the second electrodes which are connected each other; the operation method for the semiconductor device including the steps of:
applying a predetermined voltage, which is higher than a voltage applied to the second electrodes of the first switching element and the second switching element, to the first electrode of the first switching element and the second switching element through the third switching element in the case of (a); and
applying a predetermined voltage, which is lower than a voltage applied to the second electrodes of the first switching element and the second switching element, to the first electrodes of the first switching element and the second switching element through the third switching element in the case of (b).
Furthermore, an operation method for a semiconductor device, wherein the semiconductor device, including: a first switching element, a second switching element, and at least one third switching element; wherein the third switching element includes a first terminal and a second terminal, each of the first switching element and the second switching element includes an ion conductor, a first electrode which is disposed so as to have contact with the ion conductor and supplies metal ions to the ion conductor, and a second electrode which is disposed so as to have contact with the ion conductor and is less susceptible to ionization than the first electrode;
(a) the first electrode of the first switching element and the first electrode of the second switching element are electrically connected each other, and a first terminal of the third switching element is electrically connected to only the first electrodes which are connected each other or
(b) the second electrode of the first switching element and the second electrode of the second switching element are electrically connected each other, and a first terminal of the third switching element is electrically connected to only the second electrodes which are connected each other; the operation method for the semiconductor device including the steps of:
applying a predetermined voltage, which is lower than a voltage applied to the second electrodes of the first switching element and the second switching element, to the first electrodes of the first switching element and the second switching element through the third switching element in the case of (a); and
applying a predetermined voltage, which is higher than a voltage applied to the second electrodes of the first switching element and the second switching element, to the first electrode of the first switching element and the second switching element through the third switching element in the case of (b).
Effect of the Invention
According to the present invention, it is possible to realize the semiconductor device which can achieve the high reliability and perform low-voltage operation.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A-1D show operation properties of a unipolar type switching element.
FIG. 2A-2D show operation properties of a bipolar type switching element.
FIG. 3(A) is a circuit diagram showing a part of a semiconductor device according to an exemplary embodiment of the present invention, and FIG. 3(B) is a cross section view showing a part of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 4(A) is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention, and FIG. 4(B) is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 5 is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 6 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 7 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 8 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 9(A) is a circuit diagram showing a part of the semiconductor device according to the exemplary embodiment of the present invention, and FIG. 9(B) is a cross section view showing a part of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 10(A) is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention, and FIG. 10(B) is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 11 is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 12 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 13 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 14 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 15 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 16 is a schematic view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 17 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 18 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 19 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 20 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 21 is a circuit diagram showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 22 is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 23 is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 24 is a cross section view showing an example of the semiconductor device according to the exemplary embodiment of the present invention.
FIG. 25 is a cross section view showing an example of the semiconductor device according to examples of the present invention.
FIG. 26A-26C show operation properties of the semiconductor device according to the example of the present invention.
FIG. 27A-27B show operation properties of the semiconductor device according to the example of the present invention.
FIG. 28 shows operation properties of a semiconductor device according to the background art and operation properties of the semiconductor device according to the example of the present invention.



DESCRIPTION OF EMBODIMENTS
The meaning of terminology related to the present invention will be described before describing the present invention in detail.
(Description of Bipolar Type Switching Element and Unipolar Type Switching Element)
(Unipolar Type Switching Element)
A unipolar type switching element means a switching element which switches between an OFF state and an ON state according to a level of an applied voltage. The OFF state means a state of high electrical resistance. The ON state means a state of low electrical resistance. The operation properties of the unipolar type switching element will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing the operation properties of the unipolar type switching element.
For example, in the case of a unipolar type variable resistance element which includes a first electrode, a switching element and a second electrode, if a positive voltage is applied to the first electrode (FIG. 1(A)), the switching element transits from the OFF state to the ON state with an intended set voltage used as a threshold voltage. That is, it transits from the state of high electrical resistance to the state of low electrical resistance. Here, the threshold voltage depends on a film thickness, composition, density, or the like of a variable resistance layer. Next, if the positive voltage is applied again to the first electrode of the switching element in the ON state (FIG. 1 (B)), the switching element transits from the ON state to the OFF state with an intended reset voltage used as a threshold voltage. If the positive voltage is applied continuously, it reaches a set voltage, and then the switching element transits from the OFF state to the ON state again.
On the other hand, if a negative voltage is applied to the first electrode (FIG. 1 (C)), the switching element transits from the OFF state to the ON state with an intended set voltage used as a threshold voltage. That is, it transits from the state of high electrical resistance to the state of low electrical resistance. Next, if the negative voltage is applied again to the first electrode of the switching element in the ON state (FIG. 1(D)), the switching element transits from the ON state to the OFF state with an intended reset voltage used as a threshold voltage.
As mentioned above, the operation shown in FIGS. 1(A) to 1(B) and the operation shown in FIGS. 1(C) to 1(D) are symmetrical. The unipolar type switching element is defined as an element that has variable resistance properties independent of the direction of applying the voltage, that is, the polarity of the applied voltage and only dependent on the level of the applied voltage.
(Bipolar Type Switching Element)
A bipolar type switching element means a switching element which switches between an OFF state and an ON state according to a polarity of an applied voltage. The OFF state means a state of high electrical resistance. The ON state means a state of low electrical resistance. The operation properties of the bipolar type switching element will be described with reference to FIG. 2. FIG. 2 is a schematic diagram showing the operation properties of the bipolar type switching element.
For example, in the case of the bipolar type switching element which includes a first electrode, an ion conductor and a second electrode, if a positive voltage is applied to the first electrode (FIG. 2(A)), the switching element transits from the OFF state to the ON state with an intended set voltage used as a threshold voltage. Next, if the positive voltage is applied again to the first electrode of the variable resistance element in the ON state (FIG. 2(B)), the switching element shows ohmic current versus voltage properties. Next, if a negative voltage is applied to the first electrode (FIG. 2(C)), the switching element transits from the ON state to the OFF state with an intended reset voltage used as a threshold voltage. That is, it transits from the state of low electrical resistance to the state of high electrical resistance. Furthermore, in the case that the positive voltage is applied again to the first electrode of the variable resistance element in the OFF state (FIG. 2(D)), the switching element transits from the OFF state to the ON state at an intended threshold voltage (set voltage). As mentioned above, it is defined as the bipolar type switching element is defined as an element that transits between the OFF state and the ON state according to the polarity of the applied voltage. In other words, the bipolar type switching element is defined as an element that transits between the state of high electrical resistance and the state of low electrical resistance according to the polarity of the applied voltage.
(Definition of Electrode Used in Bipolar Type Variable Resistance Element)
Here, an electrode, which is used in the bipolar type switching element, will be defined. As described in FIG. 2, in the case that the positive voltage is applied to an electrode and then the switching element transits from the OFF state to the ON state, the electrode is defined as the first electrode or an active electrode. On the other hand, in the case that the positive voltage is applied to an electrode and then the switching element transits from the ON state to the OFF state, the electrode is defined as the second electrode or an inactive electrode. The first electrode supplies an ion to the ion conductor, and the second electrode is less susceptible to ionization than the first electrode.
In the case of connecting two switching elements which are different each other, two electrodes are electrically connected each other. Then, a case, in which the active electrodes of the switching elements different each other or the inactive electrodes of the switching elements different each other are electrically connected each other or are unified, is defined as a connection between the electrodes which have the same polarity. On the other hand, a case, in which the active electrode in one of two switching elements which are different each other, and the inactive electrode in the other of them are connected, is defined as a connection between the electrodes which have the different polarities.
Hereinafter, exemplary embodiments and preferred examples according to the present invention will be described in detail using the bipolarity type switching element as the switching element.
<First Exemplary Embodiment>
FIG. 3(A) is a schematic diagram showing the constitution of a semiconductor device according to a first exemplary embodiment. FIG. 3(B) shows a structure of the semiconductor device, while FIG. 3(A) shows a circuit diagram of the semiconductor device. The semiconductor device shown in FIG. 3 (A) includes a first switching element 1, a second switching element 2, and at least one third switching element 3. The third switching element 3 includes first and second terminals 31 and 32. Each of the first and the second switching elements 1, 2 includes ion conductors 13, 23, first electrodes 11, 21 which are disposed contacting with the ion conductors 13, 23 and supplies the metal ion to the ion conductors 13, 23, and second electrodes 12, 22 which are disposed contacting with the ion conductors 13, 23 and are less susceptible to ionization than the first electrodes 11, 21, respectively. The first electrode 11 of the first switching element 1 and the first electrode 21 of the second switching element 2 are electrically connected each other, and the first terminal 31 of the third switching element 3 is electrically connected to only the first electrodes 11 and 21 which are connected each other. The semiconductor device shown in FIG. 3 (A) has the constitution mentioned above.
A material, which includes any one of an organic matter, organosiloxane, silicon carbide oxide, tantalum silicon oxide, tantalum oxide, zirconium oxide, hafnium oxide, silicon oxide and titanium oxide, is available for the ion conductor. Moreover, Cu-based material is available for the first electrode. A material, which includes Ru or Pt, is available for the second electrode. Here, Cu-based means that a Cu content rate is not smaller than 95%. Generally, if the Cu content rate becomes not larger than 95%, a wiring resistance increases.
The operation of the semiconductor device according to the first exemplary embodiment will be described below. States of the first switching element 1 and the second switching element 2 of the semiconductor device according to the present exemplary embodiment are programmed to set the state of high electrical resistance. Here, the state of high electrical resistance means a state that the ion is not conducted from the first electrode 11 of the first switching element 1 and the first electrode 21 of the second switching element 2 to the ion conductor 13 and the ion conductor 23, respectively. Then, a positive voltage, which is not higher than a threshold voltage (set voltage), is applied to the second electrode 12 of the first switching element 1, and the second electrode 22 of the second switching element 2 is grounded. As a result, the voltage is applied between both ends of each of the switching elements 1 and 2, while the voltage is applied to the second switching element 2 in the direction of transiting from the OFF state to the ON state, and the voltage is applied to the first switching element 1 in the direction of transiting from the ON state to the OFF state. That is, since the direction of applying the voltage to the second switching element 2 is coincident with the direction to make the second switching element 2 transit to the ON state, if a voltage not higher than the threshold voltage is applied, there is the potential for transiting to the ON state due to an erroneous operation. Meanwhile, since the direction of applying the voltage in the first switching element 1 is coincident with the direction of transiting to the OFF state, even if a voltage not higher than the threshold voltage is applied, the erroneous operation does not arise. Here, the transition to the ON state means that the ion is conducted from the first electrode 21 to the ion conductor 23. Meanwhile, the case will be taken into consideration below that a positive voltage, which is not higher than a threshold voltage (set voltage), is applied to the second electrode 22 of the second switching element 2 and the second electrode 12 of the first switching element 1 is grounded. In this case, the voltage is applied in the first switching element 1 in the direction of transiting from the OFF state to the ON state, and in contrast, the voltage is applied in the second switching element 2 in the direction of transiting from the ON state to the OFF state. That is, since the direction of applying the voltage in the first switching element 1 is coincident with the direction of transiting to the ON state, if a voltage not higher than the threshold voltage is applied, there is the potential for transiting to the ON state due to an erroneous operation. Meanwhile, since the direction of applying the voltage in the second switching element 2 is coincident with the direction of transiting to the OFF state, even if a voltage not higher than the threshold voltage is applied, the erroneous operation does not arise. Here, the transition to the ON state means that the ion is conducted from the first electrode 11 to the ion conductor 13.
As mentioned above, it is possible to maintain the OFF state in either the first switching element or the second switching element by the constitution according to the present exemplary embodiment, even if any signal form is transmitted. As a result, it is possible to eliminate the erroneous operation of transiting from the OFF state to the ON state, that is, to prevent the disturb failure. Therefore, it is possible to eliminate the imperfection due to the erroneous operation of the semiconductor circuit, and to realize the semiconductor device which has high reliability and can perform low-voltage operation. Moreover, since each of the voltages, which are applied to the first switching element and the second switching element is divided by each electrical resistance value of the first switching element and the second switching element into almost half voltage by resistor divider, it is possible to prevent the disturb failure.
(Modified Example According to the First Exemplary Embodiment)
FIG. 4(A) is a modified example of the semiconductor device shown in FIG. 3(A). FIG. 4(B) shows the structure of the semiconductor device, while FIG. 4(A) shows a circuit diagram of the semiconductor device. As shown in FIG. 4(A), it is possible to unify the first electrode 11 of the first switching element 1 with the first electrode 21 of the second switching element 2. Because of the constitution, it becomes possible to miniaturize the semiconductor device, and to reduce transmission loss of a control signal. Moreover, it is also possible to unify the ion conductor 13 of the first switching element 1 with the ion conductor 23 of the second switching element 2 as shown in FIG. 5 as long as the first electrodes of the first switching element and the second switching element are electrically connected each other.
<Second Exemplary Embodiment>
(Programming Method of Switching Element)
The method for programming the switching element according to the first exemplary embodiment will be described below. FIG. 6 is a schematic diagram showing a semiconductor device according to the second exemplary embodiment. As shown in FIG. 6, first electrodes of a first switching element 1 and a second switching element 2, and a drain of a first transistor 63 are electrically connected each other. Here, the first electrode 11 of the first switching element 1 and the first electrode 21 of the second switching element 2 are the active electrodes. A drain of a second transistor 61 is electrically connected to the second electrode 12 of the first switching element 1. Here, the second electrode 12 of the first switching element 1 is the inactive electrode. And a drain of a third transistor 65 is electrically connected to the second electrode 22 of the second switching element 2.
For example, if an electric signal is transmitted from a terminal 51 to a terminal 52, it is necessary to make both of the first switching element 1 and the second switching element 2 transit to the ON state, that is, the state of low electrical resistance. In this case, it is possible to realize the intended transition to the ON state by grounding a terminal V1 and a terminal V3, by applying to a terminal V2 a predetermined voltage, that is, a positive voltage which is not lower than a threshold voltage (set voltage) of the switching element, and consequently by making the second transistor 61, the first transistor 63 and the third transistor 65 transit to the state of low electrical resistance. On the other hand, in the case of cutting off an electrical signal transmitting from the terminal 51 to the terminal 52, it is necessary to make both of the first switching element 1 and the second switching element 2 transit to the OFF state, that is, the state of high electrical resistance. In this case, it is possible to realize the intended transition to the OFF state by grounding the terminal V2, by applying to the terminals V1 and V3 a positive voltage which is not lower than a threshold voltage (reset voltage) of the switching element, and consequently by making the second transistor 61, the first transistor 63 and the third transistor 65 transit to the state of low electrical resistance.
It is not necessary that the predetermined voltage is higher than the threshold voltage. It is also possible to make the state of the switching element transit over time by applying a voltage, which is lower than the threshold voltage for a long time, for example.
<Third Exemplary Embodiment>
(Rewriting Circuit 1 Using P Type MIS and N Type MIS)
A semiconductor device according to a third exemplary embodiment is the same as the semiconductor device according to the second exemplary embodiment except that a programming method of the switching element is different from that of the second exemplary embodiment. FIG. 7 is a schematic diagram showing the semiconductor device according to the third exemplary embodiment. As shown in FIG. 7, a first electrode of a first switching element 1 and a first electrode of a second switching element 2, a drain of a first P type MIS (Metal Insulator Semiconductor) transistor 43 and a drain of a first N type MIS transistor 44, are electrically connected each other, respectively. Here, the first electrode 11 of the first switching element 1 and the first electrode 21 of the second switching element 2 are the active electrodes. A drain of a second P type MIS transistor 41 and a drain of a second N type MIS transistor 42 are electrically connected to the second electrode 12 of the first switching element 1. Here, the second electrode 12 of the first switching element 1 is the inactive electrode. A drain of a third P type MIS transistor 45 and a drain of a third N type MIS transistor 46 are electrically connected to the second electrode 22 of the second switching element 2.
The operation will be described below. By putting the MIS transistors 41, 42, 45 and 46 into the state of low electrical resistance, and putting the MIS transistors 43 and 44 into the state of high electrical resistance, both of the first switching element 1 and the second switching element 2 are put into the state of high electrical resistance. Then, similarly to the second exemplary embodiment, a positive voltage which is not higher than a threshold voltage (set voltage) is applied through the terminal 51, and the terminal 52 is grounded. As a result, while the voltage is applied between both ends of each of switching elements 1 and 2, the first switching element 1 does not malfunction even if a voltage not higher than the threshold voltage is applied, because the direction of applying the voltage to the first switching element 1 is coincident with the direction for the first switching element 1 to transit to the OFF state. On the other hand, in the case that a positive voltage which is not higher than the threshold voltage (set voltage) is applied to the terminal 52, and the terminal 51 is grounded, since the direction of applying the voltage to the second switching element 2 is coincident with the direction for the second switching element 2 to transit to the OFF state, the second element 2 does not malfunction, even if a voltage which is not higher than the threshold voltage is applied.
As mentioned above, it is possible to maintain the OFF state of either the first switching element or the second switching element by the constitution according to the present exemplary embodiment, even if any signal form is transmitted. As a result, it is possible to prevent the erroneous operation of transiting from the OFF state to the ON state, that is, the disturb failure. Therefore, by the constitution mentioned above, it is possible to eliminate the imperfection due to the erroneous operation of the semiconductor circuit, and to realize the semiconductor device which has high reliability and can perform low-voltage operation. As the typical MIS transistor, a MOS (Metal Oxide Semiconductor) transistor can be used. And, by connecting a P type MOS transistor to a power supply, and connecting an N type MOS transistor to the ground, it is possible to obtain intended performance. For example, if the N type MOS transistor is connected to the power source, a source of the transistor becomes floating, and consequently the performance is degraded.
(Rewriting Circuit 2 Using P Type MIS and N Type MIS)
A semiconductor device shown in FIG. 8 has a constitution in which the third P type MIS transistor 45 is omitted in the semiconductor device shown in FIG. 7.
As shown in FIG. 8, the first electrode of the first switching element 1 and the first electrode of the second switching element 2, the drain of the first P type MIS transistor 43 and the drain of the first N type MIS transistor 44, are electrically connected each other, respectively. The drain of the second P type MIS transistor 41 is connected to both of the second electrode 12 of the first switching element 1 and the second electrode 22 of the second switching element 2. The drain of the second P type MIS transistor 41 and the drain of the second N type MIS transistor 42 are electrically connected to the second electrode 12 of the first switching element 1. The drain of the third N type MIS transistor 46 is electrically connected to the second electrode 22 of the second switching element 2.
By the composition, the number of the transistors becomes smaller than that of the semiconductor device shown in FIG. 7, and it is possible to realize the fine and simple semiconductor device.
Similarly, it is also possible to omit the second P type MIS transistor 41 and to electrically connect the drain of the third P type MIS transistor 45 to both the second electrode 12 of the first switching element and the second electrode 22 of the second switching element 2. As the typical MIS transistor, a MOS (Metal Oxide Semiconductor) transistor can be used.
<Fourth Exemplary Embodiment>
A semiconductor device according to a fourth exemplary embodiment has a constitution in which the second electrodes of the first and the second switching elements instead of the first electrodes thereof are electrically connected each other in the semiconductor device according to the first exemplary embodiment. FIG. 9(A) is a schematic diagram showing the constitution of the semiconductor device according to the fourth exemplary embodiment. FIG. 9(B) shows the structure of the semiconductor device, while FIG. 9(A) shows a circuit diagram of the semiconductor device. The semiconductor device shown in FIG. 9(A) includes the first switching element 1, the second switching element 2, and at least one of third switching elements 3. The third switching element 3 includes the first terminal 31 and the second terminal 32. Each of the first and the second switching elements 1, 2 includes the ion conductor 13, 23, the first electrode 11, 21 which is disposed contacting with the ion conductor 13, 23 and supplies the metal ion to the ion conductor 13, 23, and the second electrode 12, 22 which is disposed contacting with the ion conductor 13, 23 and is less susceptible to ionization than the first electrode 11, 21, respectively. The second electrode 12 of the first switching element 1 and the second electrode 22 of the second switching element 2 are electrically connected each other, and the first terminal 31 of the third switching element 3 is electrically connected to only the second electrodes 12 and 22 which are connected each other. The semiconductor device shown in FIG. 9(A) has the constitution mentioned above.
The operation of the semiconductor device according to the fourth exemplary embodiment will be described below. States of the first switching element 1 and the second switching element 2 in the semiconductor device according to the present exemplary embodiment are programmed to set the state of high electrical resistance. And then, a positive voltage which is not higher than a threshold voltage (set voltage) is applied to the first electrode 11 of the first switching element 1, and the first electrode 21 of the second switching element 2 is grounded. In this case, since the direction of applying the voltage to the first switching element 1 is coincident with the direction of transiting to the ON state, if a voltage not higher than the threshold voltage is applied, there is the potential for transiting to the ON state due to an erroneous operation. On the other hand, since the direction of applying the voltage to the second switching element 2 is coincident with the direction of transiting to the OFF state, the erroneous operation does not arise, even if a voltage not higher than the threshold voltage is applied. Here, the transition to the ON state means that the ion is conducted from the first electrode 11 to the ion conductor 13. Meanwhile, the case will be taken into consideration below that a positive voltage which is not higher than a threshold voltage (set voltage) is applied to the first electrode 21 of the second switching element 2, and the first electrode 11 of the first switching element 1 is grounded. In this case, since the direction of applying the voltage to the second switching element 2 is coincident with the direction of transiting to the ON state, if a voltage not higher than the threshold voltage is applied, there is the potential for the second switching element 2 transiting to the ON state due to the erroneous operation. On the other hand, since the direction of applying the voltage to the first switching element 1 is coincident with the direction of transiting to the OFF state, the erroneous operation does not arise, even if a voltage not higher than the threshold voltage is applied. Here, the transition to the ON state means that the ion is conducted from the first electrode 21 to the ion conductor 23.
As mentioned above, the constitution in which the second electrodes are connected each other has the same effect as the constitution in which the first electrodes are connected each other does. That is, since it is possible to maintain the OFF state of either the first switching element or the second switching element even if any signal form is transmitted, it is possible to prevent the disturb failure. Furthermore, it becomes possible to miniaturize the semiconductor device because according to the constitution connecting the second electrodes each other, the first electrode and the wiring layer can be unified when the constitution is realized in the multi-layered wiring layer.
(Modified Example of Fourth Exemplary Embodiment)
FIG. 10(A) is a modified example of the semiconductor device shown in FIG. 9(A). FIG. 10(B) shows a structure of the semiconductor device, while FIG. 10(A) shows a circuit diagram of the semiconductor device. As shown in FIG. 10(A), it is possible to unify the second electrode 12 of the first switching element 1 and the second electrode 22 of the second switching element 2. By the constitution, it is possible to miniaturize the semiconductor device, and to reduce transmission loss of a control signal. As long as the second electrodes are electrically connected each other, it is also possible to unify the ion conductor 13 of the first switching element 1 and the ion conductor 23 of the second switching element 2 as shown in FIG. 11, for example.
<Fifth Exemplary Embodiment>
(Programming Method of Switching Element)
The method for programming the switching element according to the fourth exemplary embodiment will be described below. FIG. 12 is a schematic diagram showing a semiconductor device according to a fifth exemplary embodiment. The semiconductor device shown in FIG. 12 has a constitution in which the second electrodes of the first and the second switching elements instead of the first electrodes thereof are electrically connected each other in the semiconductor device shown in FIG. 6. As shown in FIG. 12, the second electrode of the first switching element 1, the second electrode of the second switching element 2, and the drain of the first transistor 63 are electrically connected each other. Moreover, the drain of the second transistor 61 is electrically connected to the first electrode 11 of the first switching element 1. And the drain of the third transistor 65 is electrically connected to the first electrode 21 of the second switching element 2. The method for programming of the switching element is the same as that described in FIG. 6.
<Sixth Exemplary Embodiment>
(Rewriting Circuit 1 Using P Type MIS and N Type MIS)
FIG. 13 is a schematic diagram showing a semiconductor device according to a sixth exemplary embodiment. The semiconductor device shown in FIG. 13 has a constitution in which the second electrodes of the first and the second switching elements instead of the first electrodes thereof are electrically connected each other in the semiconductor device shown in FIG. 7. As shown in FIG. 13, the second electrode of the first switching element 1, the second electrode of the second switching element 2, the drain of the first P type MIS transistor 43, and the drain of the first N type MIS transistor 44 are electrically connected each other. The drain of the second P type MIS transistor 41 and the drain of the second N type MIS transistor 42 are electrically connected to the first electrode 11 of the first switching element 1. The drain of the third P type MIS transistor 45 and the drain of the third N type MIS transistor 46 are electrically connected to the first electrode 21 of the second switching element 2. According to the constitution which the second electrodes are connected each other, it is possible to improve the disturb failure and to realize the semiconductor device, which has high reliability and can perform low-voltage operation, similarly to the constitution in which the first electrodes are connected each other.
As the typical MIS transistor, a MOS (Metal Oxide Semiconductor) transistor can be used. And, it is possible to obtain intended performance by connecting the P type MOS transistor to a power supply, and grounding the N type MOS transistor. For example, if the N type MOS transistor is connected to the power source, a source of the transistor becomes floating, and consequently the performance is degraded.
(Rewriting Circuit 2 Using P Type MIS and N Type MIS)
A semiconductor device shown in FIG. 14 has a constitution in which the third N type MIS transistor 46 is omitted and the drain of the second N type MIS transistor 42 is electrically connected to both of the first electrode 11 of the first switching element 1 and the first electrode 21 of the second switching element 2.
As shown in FIG. 14, the second electrode of the first switching element 1, the second electrode of the second switching element 2, the drain of the first P type MIS transistor 43 and the drain of the first N type MIS transistor 44 are electrically connected each other. The drain of the second N type MIS transistor 42 is connected to both of the first electrode 11 of the first switching element 1 and the first electrode 12 of the second switching element 2. Furthermore, the drain of the second P type MIS transistor 41 and the drain of the second N type MIS transistor 42 are electrically connected to the first electrode 11 of the first switching element 1. The drain of the third P type MIS transistor 45 is electrically connected to the first electrode 22 of the second switching element 2.
By the constitution, the number of the transistors becomes smaller than that of the semiconductor device shown in FIG. 13, and it is possible to realize the fine and simple semiconductor device.
Similarly, it is also possible to omit the second N type MIS transistor 42, and to electrically connect the drain of the third N type MIS transistor 46 to both of the first electrode 11 of the first switching element 1 and the first electrode 21 of the second switching element 2.
As the typical MIS transistor, a MOS (Metal Oxide Semiconductor) transistor can be used.
<Seventh Exemplary Embodiment>
(Structure of Crossbar Switch)
FIG. 15 is a circuit diagram of a crossbar switch which uses the semiconductor device according to the present invention. FIG. 16 is a layout diagram of the crossbar switch which uses the semiconductor device according to the present invention, and is a schematic diagram showing a top view. Here, a cell according to the present invention will be defined. The cell according to the present invention is defined as a unit structure which is disposed periodically in a semiconductor integrated circuit, and includes the first switching element, the second switching element, and the first transistor as the third switching element. The crossbar switch shown in FIG. 15 has the structure that a plurality of first wirings 71 and a plurality of second wirings 72 are disposed additionally. One of first wirings 71 selected from the plurality of first wirings and a drain of a switching transistor, for example, the drain of the second transistor 61 according to the second exemplary embodiment, are electrically connected each other. One of second wirings 72 selected from the plurality of second wirings and a drain of a switching transistor, for example, the drain of the third transistor 65 according to the second exemplary embodiment, are electrically connected each other. In each of plural cells 100 which compose one column of a matrix, the second electrode of the first switching element and one of the first wirings are electrically connected each other. In each of the plural cells 100 which compose one row of the matrix, the second electrode of the second switching element and one of the second wirings are electrically connected each other. Furthermore, the crossbar switch includes a plurality of third wirings. In each of the plural cells 100 which compose one row or one column, one of the third wirings selected from the plurality of third wirings and a gate of a switching transistor, for example, the gate of the first transistor 63 according to the second exemplary embodiment, are electrically connected each other.
Although a plurality of wirings which are arranged in the direction of the column are defined as the first wiring, and a plurality of wirings which are arranged in the direction of the row are defined as the second wiring according to the present exemplary embodiment, it goes without saying that a plurality of the wirings which are arranged in the direction of the row are defined as the first wiring, and a plurality of the wirings which are arranged in the direction of the column are defined as the second wiring. It is also possible to use the P type MIS transistors 41, 43 and 45 and the N type MIS transistors 42, 44 and 46 as the switching transistor as shown in FIG. 17 and FIG. 18.
By the constitution, it is possible to realize the crossbar switch which has high reliability and can perform low-voltage operation. Moreover, by using the crossbar switch which has the composition mentioned above, it becomes possible to change a signal transmission path arbitrarily after production of a semiconductor chip without consuming standby electrical power. Moreover, by installing a switching part of the crossbar switch in the multi-layered wiring layer, the switching part can be disposed in a small area, therefore, it is possible to reduce charge and discharge current when transmitting a signal, and thereby it is also advantageous for reducing the operating electrical power. Furthermore, once the crossbar switch is programmed, it can transmit the signal by using an operating voltage of the logic circuit, and thereby it is possible to perform low-voltage operation.
As shown in FIGS. 19 to 21, even though the second electrodes of the first switching element and the second switching element are electrically connected each other, it is possible to compose a crossbar switch similar to the structure which is applied in the case that the first electrodes of the first switching element and the second switching element are electrically connected each other.
<Eighth Exemplary Embodiment>
(Structure of Device Whose First Electrodes (Active Electrodes) are Connected Each other)
In the present exemplary embodiment, a structure will be described which is used for realizing the semiconductor device according to the first exemplary embodiment in the multi-layered wiring layer, that is, a structure of a semiconductor device in which the first electrodes (active electrodes) of a two-switching element are electrically connected each other. Here, each first electrode of the two-switching elements is the active electrode.
FIG. 22 is a cross section view showing the semiconductor device according to the present exemplary embodiment schematically. The semiconductor device shown in FIG. 22 has the structure in which two switching elements according to the first exemplary embodiment are disposed in the multi-layered wiring layer mounted on a semiconductor substrate. That is, the semiconductor device shown in FIG. 22 includes an interlayer insulating film 102, a barrier insulating film 103, an interlayer insulating film 104, a second electrode 105, a barrier metal 106, an insulative barrier film 107, a protective insulating film 108, an ion conductor 109, a first electrode 110, interlayer insulating films 111 and 112, wirings 114a and 114b, plugs 115a and 115b, a barrier metal 116, and a barrier insulating film 117.
Each switching element has the first electrode 105, the second electrode 110 and the ion conductor 109 which is interposed between the first electrode 105 and the second electrode 110. A single first electrode 105 is formed by unifying the first electrodes of two switching elements. In the multi-layered wiring layer, the first electrode 105 is a wiring combining a lower electrode, and the ion conductor 109 has contact with the lower electrode and wiring 105 at an opening of the barrier film 107. The second electrode 110, which is an upper electrode, is electrically connected to the two separate wirings 114a and 114b through the two separate plugs 115a and 115b respectively.
By the constitution mentioned above, it is possible to eliminate the imperfection due to the erroneous operation of the semiconductor circuit, and to realize the semiconductor device which has high reliability and can perform low-voltage operation, as shown in the exemplary embodiment. In the present exemplary embodiment, a material which becomes the source of a metal ion, for example, Cu-based material is available for the first electrode. In the present exemplary embodiment, a material which is less susceptible to ionization than the second electrode, for example, Ru or Pt is applicable to the second electrode. In the exemplary embodiment, a material which can conduct the metal ion, for example, a material which includes any one of an organic matter, organosiloxane, silicon carbide oxide, tantalum silicon oxide, tantalum oxide, zirconium oxide, hafnium oxide, silicon oxide and titanium oxide is available for the ion conducting layer. Here, Cu-based means that a Cu content rate is not smaller than 95%. Generally, in the case that the Cu content rate becomes not larger than 95%, a wiring resistance increases.
<Ninth Exemplary Embodiment>
(Structure 1 of Device Whose Inactive Electrodes (Second Electrodes) are Connected Each other)
In the present exemplary embodiment, a structure will be described which is used for realizing the semiconductor device according to the fourth exemplary embodiment in the multi-layered wiring layer, that is, a structure of a semiconductor device whose second electrodes are electrically connected each other. Here, the second electrode is the inactive electrode.
FIG. 23 is a cross section view showing the semiconductor device according to the present exemplary embodiment schematically. The semiconductor device shown in FIG. 23 has the structure in which two switching elements according to the fifth exemplary embodiment are disposed in the multi-layered wiring layer which is mounted on a semiconductor substrate. That is, the semiconductor device shown in FIG. 23 includes the interlayer insulating film 102, the barrier insulating film 103, the interlayer insulating film 104, second electrodes 105a and 105b, barrier metals 106a and 106b, the insulative barrier film 107, the protective insulating film 108, the ion conductor 109, the first electrode 110, the interlayer insulating films 111 and 112, a hard mask 113 for the interlayer insulating film, a wiring 114, the plugs 115a and 115b, the barrier metal 116, and the barrier insulating film 117.
Each switching element has the first electrodes 105a and 105b, the second electrode 110, and the ion conductor 109 which is interposed between the first electrodes 105a, 105b and the second electrode 110. A single second electrode 110 is formed by unifying the second electrodes of two switching elements. In the multi-layered wiring layer, the first electrodes 105a and 105b are wirings combining lower electrodes. The ion conductor 109 has contact with the two separate lower electrode and wiring 105a and 105b at two openings of the barrier film 107. The unified second electrode 110 is an upper electrode, and is electrically connected to the wiring 114 through the two separated plugs 115a and 115b. By the constitution mentioned above, it is possible to eliminate the imperfection due to the erroneous operation of the semiconductor circuit, and to realize the semiconductor device which has high reliability and can perform low-voltage operation.
In the present exemplary embodiment, a material which becomes the source of the metal ion, for example, Cu-based material is available for the first electrode. In the present exemplary embodiment, a material which is less susceptible to ionization than the second electrode, for example, Ru or Pt is available for the second electrode. In the present exemplary embodiment, a material which can conduct the metal ion, for example, a material which includes any one of an organic matter, organosiloxane, silicon carbide oxide, tantalum silicon oxide, tantalum oxide, zirconium oxide, hafnium oxide, silicon oxide and titanium oxide is available for the ion conducting layer. Here, Cu-based means that a Cu content rate is not smaller than 95%. Generally, if the Cu content rate becomes not larger than 95%, a wiring resistance increases.
(Structure 2 of Device Whose Inactive Electrodes are Connected Each other)
FIG. 24 is a schematic diagram showing a modified example of the semiconductor device shown in FIG. 23. A semiconductor device shown in FIG. 24 has the constitution in which the ion conductor 109 has contact with the two separate lower electrode and wiring 105a and 105b at an opening of the barrier film 107 in the semiconductor device shown in FIG. 23. The second electrode 110 which is the unified upper electrode is electrically connected to the wiring 114 through the plug 115. By the constitution mentioned above, it is possible to eliminate the imperfection due to the erroneous operation of the semiconductor circuit, and to realize the semiconductor device which has high reliability and can perform low-voltage operation. Furthermore, it is possible to realize the semiconductor device which is finer than the semiconductor device shown in FIG. 23. Although the case where the first wiring and the second wiring are disposed on the same layer is described in the present exemplary embodiment, it is also possible to dispose the first wiring on one layer, and the second wiring on different layers in the multi-layered wiring layer.
EXAMPLE
The semiconductor device according to the exemplary embodiment mentioned above has been implemented in the multi-layered wiring layer, and measure results on voltage versus current properties will be shown below.
First Example
FIG. 25 is a cross section view schematically showing a semiconductor device according to the present example. The semiconductor device shown in FIG. 25 has the constitution in which two switching elements are disposed in a copper multi-layered wiring layer mounted on a semiconductor substrate. Each switching element has the first electrodes 105a and 105b, the second electrode 110, and the ion conductor 109 which is interposed between the first electrodes 105a, 105b and the second electrode 110. The second electrodes of the two switching elements are unified. In the multi-layered wiring layer, the first electrodes 105a and 105b are wirings combining lower electrodes. The ion conductor 109 has contact with the two separated lower electrodes and wirings 105a and 105b at an opening of the barrier film 107.
In the present example, the first electrode is composed of Cu-based material, Ru is utilized for the second electrode, and Polymer Solid Electrolyte (PSE) is utilized for the ion conductor. Here, Cu-based means that a Cu content rate is not smaller than 95%. Comparing each terminal shown in FIG. 25 with the writing circuit shown in FIG. 12, the terminal 51 corresponds to a Source, the terminal 52 corresponds to a Drain, and the control voltage terminal V2 corresponds to a Gate. Here, the control voltage terminal V2 corresponds to the situation that the control transistor 63 is always in the ON state.
FIG. 26 shows voltage versus current properties which is obtained in applying the voltage to each terminal. Since the switching element is in the state of high electrical resistance at the initial state, an electrical resistance value between Source and Drain indicates 108Ω (OFF1 in FIG. 26(C)). Next, the voltages are applied between Gate and Drain, and between Gate and Source respectively in order to make the switching element transit to the state of low electrical resistance. At this time, if Gate is fixed to the ground, the forming operation can be carried out by applying positive voltages to Source and Drain respectively (Igs and Igd in FIG. 26(A)). At this time, the threshold voltage is equal to 2 V. The set current is controlled to be 100 μA by the transistor.
Next, measuring the voltage versus current characteristics between Source and Drain in order to check whether the switching element transits to the state of low electrical resistance, the measured results indicate about 600Ω (ON in FIG. 26(C)). Next, in order to make the switching element transit to the state of high electrical resistance, the voltages are applied between Gate and Drain, and between Gate and Source respectively. At this time, if Source and Drain are fixed to the ground, the reset operation can be carried out by applying a positive voltage to Gate (Igs and Igd in FIG. 26(B)). When the voltage is applied, the electrical current decreases around 1 V, that is, the electrical resistance value increases.
Next, measuring the voltage versus current characteristics between Source and Drain in order to check whether the switching element transits to the state of high electrical resistance, the measured results indicate about 108Ω (OFF2 in FIG. 26(C)). As mentioned above, it can be confirmed that by applying the voltage to Gate the transition to the state of high electrical resistance (OFF1 and OFF2 in FIG. 26(C)) and to the state of low electrical resistance (ON in FIG. 26(C)) can be performed with non-volatility.
Next, the reliability, that is, the disturb characteristic is measured. FIG. 27 shows the voltage versus current characteristics of the switching element with the state of high electrical resistance at 125° C. FIG. 27(A) shows current values (Ids) when applying the voltage between Drain and Source. It is understood that the insulation breakdown occurs at about 4 V. FIG. 27(B) shows current values (Igs) when applying the voltage between Gate and Source. It is understood that the switching element transits to the state of low electrical resistance at about 2 V. Accordingly, it is understood that the reliability is improved because the breakdown voltage between Drain and Source becomes larger than the programming voltage.
Here, the points, to consider when improving the reliability, that is, the disturb properties will be described below. In order to secure the reliability on the insulation between Drain and Source, it is preferable that the electrical insulation resistance between Gate and Source is as equal as possible to that between Gate and Drain. Here, the electrical insulation resistance means OFF electrical resistance. The reason is as follows: If electrical resistance values are different each other, the distribution of the applied voltages becomes out of balance, and consequently there is a possibility that a high voltage is applied to one side. That is, it is preferable to form the opening in the center between Drain and Source as far as possible.
FIG. 28 is a diagram showing the comparison between the operation properties of the two terminal type element according to the background art and the operation properties of the semiconductor device according to the present example. The two terminal type element according to the background art means a semiconductor device which includes one switching element. Comparing the operation properties of two terminal type element according to the background art with the operation properties of the semiconductor device according to the present example, it is understood that the life prediction at 1 V increases from 10 years and over to not shorter than one million years. Although the present invention is described in association with some preferable examples, these exemplary embodiments and the examples are used merely for explaining the present invention by exemplifying the actual example, and are not meant to limiting the present invention.
While the example, in which the switching element is disposed in the copper multi-layered wiring mounted on the semiconductor substrate, is described in the detailed description of the present invention, thought of the present invention is not limited to this. The present invention is applicable to, for example, semiconductor products which include memory circuits such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), the flash memory, FRAM (Ferro Electric Random Access Memory), MRAM (Magnetic Random Access Memory), and bipolar transistors, a semiconductor products which include logic circuits such as the microprocessor, or the copper wiring of a board or a package which mounts those semiconductor products.
Moreover, the present invention is applicable to joining an electronic circuit device, an optical circuit device, a quantum circuit device, a micromachine, MEMS (Micro Electro Mechanical Systems) and the like to the semiconductor device. While the example using as the switching function is mainly described in the present invention, the present invention is also applicable to a memory element which uses both of the non-volatility properties and the variable resistance properties, and the like.
The whole or part of the exemplary embodiments or the examples disclosed above can be described as, but not limited to, the following supplementary note.
(Supplementary Note 1)
A semiconductor device, comprising a first switching element, a second switching element, and at least one third switching element;
wherein the third switching element comprises a first terminal and a second terminal, wherein each of the first switching element and the second switching element comprises an ion conductor, a first electrode which is disposed so as to have contact with the ion conductor and whose main component is Cu, and a second electrode which is disposed so as to have contact with the ion conductor and which comprises Ru or Pt; and wherein
(a) the first electrode of the first switching element and the first electrode of the second switching element are electrically connected each other, and the first terminal of the third switching element is electrically connected to only the first electrodes which are connected each other or
(b) the second electrode of the first switching element and the second electrode of the second switching element are electrically connected each other, and the first terminal of the third switching element is electrically connected to only the second electrodes which are connected each other.
Although it is apparent after reading the present specification that a person skilled in the art easily carries out various changes and various modifications by use of equivalent elements and arts, is apparent that those changes and the modifications correspond to the real scope and spirit of the attached claims.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-136988, filed on Jun. 16, 2010, the disclosure of which is incorporated herein in its entirety by reference.
DESCRIPTION OF THE CODES
1 first switching element
2 second switching element
3 first transistor
11, 21 first electrode
12, 22 second electrode
13, 23 ion conductor
41 second P type MIS transistor
42 second N type MIS transistor
43 first P type MIS transistor
44 first N type MIS transistor
45 third P type MIS transistor
46 third N type MIS transistor
51, 52 input-output terminal
61 second transistor
63 first transistor
65 third transistor
71 first wiring
72 second wiring
73 third wiring
74 fourth wiring
81 upper layer wiring
82 lower layer wiring
83 via plug
84 contact plug
85 upper electrode
100 cell
102 interlayer insulating film
103 barrier insulating film
104 interlayer insulating film
105, 105a, 105b second electrode (wiring and lower electrode)
106, 106a, 106b barrier metal
107 insulative barrier film
108 protective insulating film
109 ion conductor
110 first electrode (upper electrode)
111, 112 interlayer insulating film
113 hard mask for interlayer insulating film
114, 114a, 114b wiring
115, 115a, 115b plug
116 barrier metal
117 barrier insulating film

## Claims

1. A semiconductor device, comprising:
a first switching element;
a second switching element, where the first switching element and the second switching element keep a same resistance state to work as one unified unit; and
at least one third switching element, comprising a volatile switching element, that functions to program the first and second switching elements,
wherein the third switching element comprises a first terminal and a second terminal,
wherein each of the first switching element and the second switching element comprises an ion conductor, a first electrode which is disposed so as to have contact with the ion conductor and supplies metal ions to the ion conductor, and a second electrode which is disposed so as to have contact with the ion conductor and is less susceptible to ionization than the first electrode, and
wherein:
the first electrode of the first switching element and the first electrode of the second switching element are electrically connected to each other, and the first terminal of the third switching element is electrically connected to only the first electrodes which are electrically connected to each other, or
the second electrode of the first switching element and the second electrode of the second switching element are electrically connected to each other, and the first terminal of the third switching element is electrically connected to only the second electrodes which are electrically connected to each other.

2. The semiconductor device according to claim 1, wherein the first electrode of the first switching element and the first electrode of the second switching element are electrically connected to each other.

3. The semiconductor device according to claim 2, wherein the first electrode of the first switching element and the first electrode of the second switching element are unified.

4. The semiconductor device according to claim 1, wherein the second electrode of the first switching element and the second electrode of the second switching element are electrically connected to each other.

5. The semiconductor device according to claim 2, wherein the second electrode of the first switching element and the second electrode of the second switching element are unified.

6. The semiconductor device according to claim 1, wherein:
the ion conductor has a first and a second major surface; and
both the first electrode of the first switching element and the first electrode of the second switching element are disposed so as to have contact with the first major surface of the ion conductor.

7. The semiconductor device according to claim 6, wherein the first electrode of the first switching element and the first electrode of the second switching element are electrically connected to each other.

8. The semiconductor device according to claim 7, wherein the first electrode of the first switching element and the first electrode of the second switching element are unified.

9. The semiconductor device according to claim 6, wherein both the second electrode of the first switching element and the second electrode of the second switching element are disposed so as to have contact with the second major surface of the ion conductor.

10. The semiconductor device according to claim 9, wherein the second electrode of the first switching element and the second electrode of the second switching element are electrically connected to each other.

11. The semiconductor device according to claim 10, wherein the second electrode of the first switching element and the second electrode of the second switching element are unified.

12. The semiconductor device according to claim 1, wherein:
both the first electrode of the first switching element and the first electrode of the second switching element are formed over a semiconductor substrate; and
the ion conductor is formed over the first electrode of the first switching element and the first electrode of the second switching element.

13. The semiconductor device according to claim 12, wherein the first electrode of the first switching element and the first electrode of the second switching element are electrically connected to each other.

14. The semiconductor device according to claim 13, wherein the first electrode of the first switching element and the first electrode of the second switching element are unified.

15. The semiconductor device according to claim 12, wherein both the second electrode of the first switching element and the second electrode of the second switching element are formed over the ion conductor.

16. The semiconductor device according to claim 15, wherein the second electrode of the first switching element and the second electrode of the second switching element are electrically connected to each other.

17. The semiconductor device according to claim 16, wherein the second electrode of the first switching element and the second electrode of the second switching element are unified.