JP2000349246A - Dielectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of characteristics of a ferroelectric substance layer and defective contact of an upper electrode due to hydrogen by forming an upper electrode into a laminated structure made of a metal, conductive oxide and a metal in the ferroelectric substance element. SOLUTION: This ferroelectric substance element comprises a lower electrode 13 formed on a semiconductor substrate 10, a ferroelectric substance layer formed on the lower electrode 13, and an upper electrode formed on a ferroelectric substance layer 14. The upper electrode is composed of an upper electrode layer 15 formed on the ferroelectric substance layer 14, a conductive oxide layer 16 for preventing diffusion of hydrogen with a perovskite structure formed on the upper electrode layer 15 and a metallic layer 17 formed on the conductive oxide layer 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric element, and more particularly, to a ferroelectric element in which deterioration of characteristics of a ferroelectric substance due to hydrogen and poor contact of an upper electrode are suppressed.

[0002]

2. Description of the Related Art In recent years, a non-volatile memory utilizing a high spontaneous polarization and a low coercive electric field of a ferroelectric has attracted attention. Such a nonvolatile memory includes a ferroelectric layer and upper and lower electrodes formed on the upper and lower surfaces of the ferroelectric layer. The memory thus formed can operate at a higher speed than conventional flash memories, EEPROMs and the like. That is, both the read and write speeds are DR
It is an ideal memory that can be expected to operate at the same high speed as AM.
Pb (Zr / Ti) O ₃ (PZT) having a large polarization amount or SrBi ₂ Ta ₂ O ₉ (SBT) having excellent film fatigue characteristics are used as a ferroelectric material used for this nonvolatile memory.
And the like are used.

In addition, Pt is widely used as an electrode material for forming a ferroelectric element from the viewpoint of heat resistance for both the upper electrode and the lower electrode.

Incidentally, in the process of manufacturing the ferroelectric element, there is a step of forming an SiO ₂ insulating protective layer. In this step, since a SiO ₂ insulating protective layer is formed using a source gas such as monosilane, hydrogen is generated by a decomposition reaction or the like. The generated hydrogen is activated by the catalytic action of Pt as the electrode material, and reacts with oxygen in the ferroelectric layer constituting the ferroelectric to degrade the characteristics of the ferroelectric element.

Regarding this problem, see, for example,
No. 83106 discloses that a coating layer formed of silicon nitride or palladium for blocking the passage of hydrogen is provided at an edge of an upper electrode of a ferroelectric element.

[0006] Japanese Patent Application Laid-Open No. 6-21334 discloses that
It is disclosed that a reaction preventing film made of silicon dioxide or silicon dioxide doped with phosphorus is inserted between at least one of the upper electrode and the lower electrode and the dielectric layer.

Japanese Patent Application Laid-Open No. Hei 10-12751 discloses that a conductive oxide made of RuO ₂ or IrO ₂ is formed on a Pt electrode formed on a ferroelectric layer.

Japanese Patent Application Laid-Open No. 10-12830 discloses that an electrode made of Pt or the like formed on a ferroelectric layer has
A conductive oxide made of rRuO ₃ or the like is formed, or an electrode made of Pt or the like is formed on the conductive oxide made of SrRuO ₃ or the like formed on the ferroelectric layer, and the ferroelectric layer is reduced. Has been shown to protect you.

[0009]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 5-183 is disclosed.
As disclosed in JP-A-106-106, in a configuration in which a protective layer made of silicon nitride or palladium is formed on an edge of an upper electrode and the passage of hydrogen is prevented by the protective layer, an electrode forming the protective layer and a dielectric element is formed. Alternatively, the characteristics are degraded due to stress distortion based on the difference in the coefficient of thermal expansion from the dielectric.

[0010] Further, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 10-12751, Rt is formed on a Pt electrode formed on a ferroelectric layer.
When a conductive oxide made of uO ₂ or IrO ₂ is formed, the passage of hydrogen is prevented and the reduction resistance is improved. However, when a wiring material made of TiN is formed on the electrode made of the conductive oxide, the conductive oxide reacts with TiN to form an insulating reaction layer made of TiOx. Causes poor contact.

Further, as shown in Japanese Patent Application Laid-Open No. 10-12830, when a conductive oxide such as SrRuO ₃ is formed on an electrode made of Pt or the like formed on a ferroelectric layer, the conductive Oxide and the TiN react to form TiN
An insulating reaction layer made of Ox is formed, and the conductive oxide and Ti
A contact failure between N is caused. On the other hand, when an electrode made of Pt or the like is formed on a conductive oxide made of SrRuO ₃ or the like formed on the ferroelectric layer, the ferroelectric layer is formed by the conductive oxide layer and the lower electrode. It will be sandwiched between certain metal layers. If the electrodes sandwiching the dielectric layer are different, the polarization hysteresis characteristic shifts in the voltage axis direction and becomes asymmetric due to the difference in work function. If the polarization hysteresis characteristics are asymmetric, the film fatigue characteristics decrease when a voltage is repeatedly applied, and the dielectric characteristics cannot be used effectively.
Further, there is a possibility that a contact failure between the conductive oxide and the ferroelectric layer may occur.

The present invention has been made in view of the above-mentioned problems, and provides a ferroelectric element in which characteristic deterioration of a ferroelectric layer and defective contact of an upper electrode due to hydrogen or the like are reduced.

[0013]

The present invention employs the following means in order to solve the above-mentioned problems.

[0014] In a dielectric element comprising a lower electrode formed on a semiconductor substrate, a dielectric layer formed on the lower electrode, and an upper electrode formed on the dielectric layer, the upper electrode is formed of the dielectric material. It is characterized by comprising an upper electrode layer formed on the layer, a conductive oxide layer for preventing hydrogen diffusion having a perovskite structure formed on the upper electrode layer, and a metal layer formed on the conductive oxide layer.

Further, in the above-mentioned dielectric element, the conductive oxide layer is made of a SrRuO ₃ conductive oxide.

In the above-mentioned dielectric element, the conductive oxide layer is made of LaTiO ₃ , CaCrO ₃ , SrCrO ₃
And at least one kind of conductive oxide composed of CaRuO ₃ .

In the above-mentioned dielectric element, the upper electrode layer and the metal layer forming the upper electrode include at least one kind of metal consisting of Pt, Ir and Ru.

In the above-mentioned dielectric element, the dielectric layer is composed of (Pb / A) (Zr / Ti) O ₃ (where A is L
a, Ba, Nb, Ca, Sr).

Further, in the above-described dielectric element, the dielectric layer is made of SrBi ₂ Ta _2-x Nb _x O ₉ (where x is 0 to 1).

Further, in the above-mentioned dielectric element, the dielectric layer is made of (Ba _1-x Sr _x ) TiO ₃ (where x is 0 to 0.9).

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a ferroelectric element comprising a lower electrode formed on a semiconductor substrate, a ferroelectric layer formed on the lower electrode, and an upper electrode formed on the ferroelectric layer, A conductive barrier layer made of a conductive oxide having a perovskite structure is formed on the upper electrode to prevent the diffusion of the inert gas or the reducing gas. SrRuO ₃ (SRO) is most preferred for the conductive barrier layer, but LaTiO
₃ , at least one of conductive oxides composed of CaCrO ₃ , SrCrO ₃ and CaRuO ₃ may be used.
In this case, the resistivity of each conductive barrier layer is 1 m
Ω · cm or less is desirable. Further, the thickness of the conductive barrier layer is preferably 100 to 2000 °, more preferably 100 to 500 °. Further, a metal layer of the same material as the upper electrode is formed on the conductive barrier layer.

On the upper electrode, a wiring layer made of TiN is formed in a later step. The wiring layer made of TiN is a material that is very easily oxidized. Therefore, when TiN is formed directly on the conductive barrier layer, various heat treatments after the formation of TiN cause TN near the interface between TiN and the conductive barrier layer.
It becomes easy to form iO ₂ . As a result, a contact failure occurs, a sufficient voltage cannot be applied to the ferroelectric layer, and the electrical characteristics deteriorate.

When a metal layer made of the same material as that of the upper electrode is formed on the conductive barrier layer, oxidation of the wiring layer made of TiN can be prevented, and the problem of poor contact can be solved. The same effect can be obtained even if the metal layer is not made of the same material as the upper electrode.

The electrode material of the upper electrode and the material of the metal layer formed on the conductive barrier layer are desirably at least one kind of metal consisting of Pt, Ir and Ru.
The thickness of the metal layer is preferably 100 to 1000 °, more preferably 100 to 500 °.

Further, the ferroelectric material is (Pb / A)
(Zr / Ti) O ₃ (where A is La, Ba, Nb, C
a, Sr is one element selected from Sr and partially replaces Pb), SrBi ₂ Ta _2-x Nb _x O ₉ (where x is 0
To 1) or (Ba _1-x Sr _x ) TiO ₃ (where x is 0 to 0.9).

Further, the ferroelectric layer can be formed by a sputtering method, a laser vapor deposition method or an MOCVD method performed in a mixed gas atmosphere of oxygen and an inert gas. Further, it can be produced by a spin coating method or a dip coating method using a metal alkoxide or an organic acid salt as a starting material in an atmosphere of a mixed gas of oxygen and an inert gas at normal pressure.

According to this embodiment, a conductive oxide layer for preventing hydrogen diffusion having a perovskite structure is formed on the upper electrode layer, and a metal layer is formed on the conductive oxide layer.
Even if the ferroelectric element is heated in a reducing atmosphere, hydrogen does not enter the ferroelectric layer. Furthermore, since the conductive oxide is excellent in reduction resistance, it does not impair the conductivity.

Further, since the metal layer is formed on the conductive barrier layer, it is possible to prevent oxidation of the wiring layer made of TiN, thereby preventing contact failure.

Further, since the metal layer is used for the upper electrode in contact with the ferroelectric layer, the contact with the ferroelectric layer can be maintained well.

Next, a first embodiment of the present invention will be described with reference to FIGS.

FIGS. 1 and 2 are views for explaining the present embodiment. FIG. 1 (a) is a view showing a ferroelectric element according to the present embodiment, and FIG. 1 (b) is a view showing FIG. 1 (a). FIG. 2 is a diagram showing a state in which an insulating protective layer is applied to the ferroelectric element shown in FIG. 2, and FIG. 2 is a diagram showing a change in electrical characteristics due to heat treatment. In these figures,
10 is a Si wafer, 11 is S formed on the surface of the Si wafer.
iO ₂ layer, 12 a Ti layer formed on a SiO ₂ layer, 13 a lower electrode made of Pt, 14 a ferroelectric layer formed on the lower electrode 13, 15 a Pt formed on a ferroelectric layer 14
, 16 is a conductive oxide layer made of SrRuO ₃ , and 17 is a metal layer made of Pt. Also,
Reference numeral 18 denotes a SiO2 insulating protective layer, and 19 denotes a wiring layer made of a TiN layer.

First, an SiO ₂ layer 11 was formed on the surface of a Si wafer 10 by thermal oxidation. Next, a Ti layer 12 is formed on the SiO ₂ layer 11 by a sputtering method at a thickness of 200 °, and a Pt layer is formed as a lower electrode 14 at a thickness of 2000 °.

Next, in order to form a ferroelectric layer on the lower electrode 13, a metal alkoxide solution prepared by mixing Sr, Bi, and Ta at a composition ratio of 1: 2.4: 2 is used at a rotational speed of 4000 rpm for 30 minutes. Spin coated for seconds. Thereafter, after drying at 150 ° C. for 30 minutes, further at 600 ° C. in air or oxygen.
For 30 minutes. The above operation was repeated three times to prepare a precursor layer having a thickness of 2400 °. Subsequently, as a heat treatment for crystallization, a heat treatment is performed in oxygen at 700 ° C. for 1 hour to obtain a ferroelectric layer 1 made of SrBi _2.4 Ta ₂ O _9.
4 was created.

Next, the upper electrode layer 1 is formed on the ferroelectric layer 14.
As No. 5, a Pt layer was formed at 1000 ° by a sputtering method. Further, a conductive oxide layer 16 made of SrRuO ₃ is formed as a barrier layer on the upper electrode layer 15 by sputtering at a thickness of 500 °.
A t layer was formed at 500 °.

Next, a heat treatment was performed at 650 ° C. for one hour in oxygen in order to recover damage caused by sputtering.

As described above, Pt, SrRuO ₃ and P
SrBi _2.4 T having an upper electrode with a laminated structure of
An a ₂ O ₉ ferroelectric device was prepared.

As a comparative example, an SrBi _2.4 Ta ₂ O ₉ ferroelectric element having an upper electrode formed only of a Pt layer was prepared in the same manner as in the present embodiment.

FIG. 2 shows that each ferroelectric element is made of hydrogen 3
The results obtained by performing a heat treatment for 10 minutes at each temperature in a helium gas atmosphere containing 10% and measuring electrical characteristics are shown. In the measurement of the electrical characteristics, the polarization hysteresis was measured under the condition of an applied voltage of ± 5 V. In the ferroelectric element according to the present embodiment, even when heat treatment is performed at 400 ° C., the polarization hysteresis characteristics do not change significantly. On the other hand, in the comparative example using only the upper electrode made of Pt, the polarization hysteresis characteristics deteriorated by the heat treatment at 150 ° C.

Next, as shown in FIG. 1B, an SiO ₂ insulating protective layer 18 was formed to a thickness of 2000 ° by the CVD method.
Next, an opening was formed in the SiO ₂ insulating protective layer 18 by etching to expose the metal layer 17. Next, heat treatment was performed at 450 ° C. for 30 minutes in an oxygen atmosphere to remove etching damage. Next, a TiN wiring layer 19 was formed by a sputtering method.

As a comparative example, a SrBi _2.4 Ta ₂ O ₉ ferroelectric element in which the upper electrode was formed only of IrO ₂ having excellent reduction resistance was prepared in the same manner as in the present embodiment, and this ferroelectric element was used. An SiO ₂ insulating protective layer and a TiN wiring layer were formed. Each ferroelectric element was subjected to a heat treatment at 400 ° C. for 10 minutes in a helium gas atmosphere containing 3% of hydrogen, and the polarization characteristics were measured.

In the ferroelectric element of this example, there was no significant difference in the polarization characteristics before the heat treatment. On the other hand, it was found that the polarization characteristics of the ferroelectric element of the comparative example after the heat treatment were significantly reduced. As a result of analyzing the cause, a part of TiN was found to be TiOx near the interface between IrO _{2 of} the upper electrode and TiN of the wiring layer.
It turned out that it changed into the insulating layer of. As a result, it was confirmed that a contact failure occurred between IrO _{2 of} the upper electrode and TiN of the wiring layer, and the polarization characteristics were deteriorated.

Thus, Pt, SrRuO ₃ and P
By using the upper electrode having a laminated structure made of t, it is possible to prevent oxidation of TiN. Further, a ferroelectric element having excellent reduction resistance can be obtained.

In this embodiment, Pt is used for the metal layer of the upper electrode, but at least one of Ir and Ru can be used.

Further, SrRuO is used as the conductive barrier layer.
₃ , LaTiO ₃ , CaCrO ₃ , SrCrO
_At least one of conductive oxides composed of RuO ₃ and RuO ₃ can be used.

Next, a second embodiment of the present invention will be described with reference to FIG. In the figure, 20 is a Si wafer, 21 is Si
SiO ₂ layer formed on the wafer surface, 22 a Ti layer formed on the SiO ₂ layer, 23 a lower electrode made of Pt, 24 a Pb (Zr / Ti) O ₃ (PZT) formed on the lower electrode
A ferroelectric layer, 25 is an upper electrode layer made of Ir formed on the ferroelectric layer 24, 26 is a conductive barrier layer made of a conductive oxide layer formed on the upper electrode layer 25, and 27 is a barrier layer 25 It is a metal layer made of Ir formed thereon.

First, the SiO ₂ layer 21 is formed on the surface of the Si wafer 20 by thermal oxidation. Next, a Ti layer 22 is formed on the SiO ₂ layer 21 by sputtering at a thickness of 500 °.
A Pt layer is formed on the Ti layer 22 as a lower electrode 23 at 1700 °.
Formed. Next, P is formed on the lower electrode 23 by sputtering.
A b (Zr / Ti) O ₃ ferroelectric layer 24 was formed. In addition,
The forming conditions are as follows: target material: composition ratio Pb: Zr: Ti =
1.2: 0.52: 0.48, substrate temperature: room temperature, pressure:
20 mtorr, a mixed gas atmosphere of oxygen and argon. After creating a precursor layer of 2500Å in this condition, 700 ° C. in an oxygen atmosphere, a heat treatment of 1 hour, the perovskite _{structure, Pb 1.2 Zr 0.52 Ti 0.48 0} 3
A ferroelectric layer 24 was formed.

Next, the upper electrode layer 25 is formed on the ferroelectric layer 24.
An Ir layer was formed at a thickness of 1000 ° by a sputtering method. Further, an SrCrO ₃ conductive oxide layer 26 is formed on the upper electrode layer 25 as a barrier layer by sputtering.
Then, an Ir layer is formed as the metal layer 27 by 500.
Å formed. Next, heat treatment was performed at 650 ° C. for 1 hour to recover damage due to sputtering.

As described above, the upper electrode is made of Ir, SrCrO
Pb _1.2 Zr _0.52 T having a laminated structure composed of ₃ and Ir
i was obtained _0.48 0 ₃ ferroelectric element. Next, the ferroelectric element was subjected to a heat treatment at 400 ° C. for 10 minutes in a 3% hydrogen-helium gas, and then the polarization hysteresis was measured under the conditions of an applied voltage of ± 3 V. As a result, it was confirmed that the characteristics did not deteriorate due to the heat treatment.

Further, a SiO ₂ protective layer was formed in the same manner as in Example 1, and an opening was formed on the Ir layer by etching. Next, heat treatment is performed at 400 ° C. for 10 minutes in oxygen,
Subsequently, TiN was formed by a sputtering method. Next, the ferroelectric layer on which the TiN was formed was subjected to a heat treatment at 400 ° C. for 10 minutes in a 3% hydrogen-helium gas, and the polarization characteristics were measured. As a result, no deterioration of the characteristics was observed.

Next, a third embodiment of the present invention will be described with reference to FIG. In the figure, 30 is a Si wafer, 31 is S
an SiO ₂ layer formed on the surface of the i-wafer; a Ti layer formed on the SiO ₂ layer; a lower electrode made of Ru;
Is a (Ba / Sr) TiO ₃ ferroelectric layer formed on the lower electrode, 35 is an upper electrode layer made of Ru formed on the ferroelectric layer 24, and 36 is a conductive oxide formed on the upper electrode layer 25. A conductive layer made of a material layer;
It is a metal layer made of Ru formed thereon.

First, the SiO ₂ layer 31 is formed on the surface of the Si wafer 30 by thermal oxidation. Next, a Ti layer 32 is formed on the SiO ₂ layer 31 by sputtering at a thickness of 500 °.
On the Ti layer 32, a Ru layer 1500 # was formed as the lower electrode 33. Next, on the lower electrode 33 using a sputtering method (B
a / Sr) TiO ₃ ferroelectric layer 34 was formed. In addition,
The formation conditions are target material: composition ratio Ba: Sr: Ti
= 0.75: 0.25: 1, substrate temperature: 350 ° C., pressure: 0.6 Pa, mixed gas atmosphere of oxygen and argon. After forming a precursor layer at 1500 ° C. under these conditions, heat treatment was performed at 650 ° C. for 1 hour in an oxygen atmosphere.
A Ba _0.75 Sr _0.25 TiO ₃ ferroelectric layer 34 having a perovskite structure was formed.

Next, the upper electrode layer 35 is formed on the ferroelectric layer 34.
A Ru layer was formed at a thickness of 1000 ° by a sputtering method. Further, a SrRuO ₃ conductive oxide layer 36 is formed on the upper electrode layer 35 as a barrier layer by sputtering.
Then, a Ru layer is formed as the metal layer 37 by 300.
Å formed. Next, heat treatment was performed at 650 ° C. for 30 minutes to recover damage due to sputtering.

Next, the ferroelectric element was subjected to a heat treatment in a 3% hydrogen-helium gas at 400 ° C. for 10 minutes, and then the polarization hysteresis was measured under the conditions of an applied voltage of ± 5 V. As a result, it was confirmed that the characteristics did not deteriorate due to the heat treatment.

Further, a SiO2 protective layer was formed in the same manner as in Example 1, and an opening was formed on the Ru layer by etching. Next, heat treatment is performed at 400 ° C. for 10 minutes in oxygen,
Subsequently, TiN was formed by a sputtering method. Next, the ferroelectric layer on which the TiN was formed was subjected to a heat treatment at 400 ° C. for 10 minutes in a 3% hydrogen-helium gas, and the polarization characteristics were measured. As a result, no deterioration of the characteristics was observed.

The composition ratio of the target material is B
a: Ba manufactured in the same manner as in the present example using the target material changed to Sr: Ti = 0.5: 0.5: 1.
_0.5 Sr _0.5 Ti0 ₃ dielectric element was found to have a high dielectric constant.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a diagram showing an example in which the ferroelectric element shown in the first embodiment is applied to a semiconductor device. In the figure,
50 is a Si substrate, 51 is a source region, 52 is a drain region, 53 is a gate insulating layer, 54 is a gate electrode, 55 is S
An element isolation insulating layer 56 formed on the i-substrate 50 is a plug electrode connecting the source region and the Ti wiring 521.

511 is an interlayer insulating layer formed of SiO ₂ ,
512 is a Ti wiring, 513 is a lower electrode, and 514 is SrB.
i ₂ Ta ₂ O _{3 is a} ferroelectric layer. 515 is a Pt layer, 51
Reference numeral 6 denotes a SrRuO3 conductive oxide layer, and 517 denotes a Pt layer.
21 are formed.

518 is a SiO ₂ insulating protective layer, 519 is a wiring layer in contact with the upper electrode 521, and 520 is a passivation film.

First, the element isolation insulating layer 5 is formed on the Si substrate 50.
5 is formed, and an MIS transistor including a source region 51, a drain region 52, a gate insulating layer 53, and a gate electrode 54 is formed in a region separated by the element isolation insulating layer 55. Also, S on the MIS transistor
An interlayer insulating layer 511 of iO2 is formed.

Next, the source region 51 of the interlayer insulating layer 511
A plug electrode 56 is formed on the
The wiring layer 512 is formed, and the lower electrode 513 is formed. Then form a SrBi2Ta2O ₃ ferroelectric layer 514 on the lower electrode 513, Pt layer 51 on the ferroelectric layer 514
5, SrRuO ₃ conductive oxide layer 516, Pt layer 517
Are laminated to form an upper electrode.

Next, an SiO 2 insulating protective layer 518 is formed, and then a wiring 519 that contacts the upper electrode 521 through the contact hole formed in the protective layer 518 is formed. Next, a passivation film 520 is formed.
The ferroelectric memory of this embodiment can operate at a voltage of 1.5V. Although the stack type semiconductor element has been described in the present embodiment, similar characteristics can be obtained even when applied to a planar type semiconductor device.

In the above description, a ferroelectric material is used as a material for forming a dielectric element, but it is a matter of course that a normal dielectric material can be used.

As described above, in this embodiment, the lower electrode formed on the semiconductor substrate, the ferroelectric layer formed on the lower electrode, and the upper electrode formed on the ferroelectric layer In the ferroelectric element, a conductive oxide layer having a perovskite structure for preventing hydrogen diffusion was formed on the upper electrode layer formed on the ferroelectric layer, and a metal layer was formed on the conductive oxide layer. Therefore, even if the ferroelectric element is heated in a reducing atmosphere, hydrogen does not enter the ferroelectric layer. Furthermore, since the conductive oxide is excellent in reduction resistance, it does not impair the conductivity.

Further, since the metal layer is formed on the conductive barrier layer, it is possible to prevent the wiring layer made of TiN from being oxidized and to prevent the contact failure.

Further, since the metal layer is used for the upper electrode in contact with the ferroelectric layer, the contact with the ferroelectric layer can be maintained well.

Further, since a metal material having the same work function is used for the electrodes sandwiching the ferroelectric layer, the polarization hysteresis characteristics can be prevented from being asymmetric, and the deterioration of the film fatigue characteristics can be prevented.

[0067]

As described above, according to the present invention, in the ferroelectric element, since the upper electrode is formed in a laminated structure composed of a metal, a conductive oxide and a metal, the characteristics of the ferroelectric layer due to hydrogen can be improved. It is possible to obtain a ferroelectric element in which deterioration and poor contact of the upper electrode are prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating the effect of the first embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

10, 20, 30, 50 Si wafer 11, 21, 31 SiO ₂ layer 12, 22, 32 Ti layer 13, 23, 33 Lower electrode 14, 24, 34 Ferroelectric layer 15, 25, 35 Upper electrode layer 16, 26, 36 Conductive oxide layer 17, 27, 37 Metal layer 18, 28, 38 SiO ₂ insulating protective layer 19, 29, 39 Wiring layer 51 Source region 52 Drain region 53 Gate insulating layer 54 Gate electrode 55 Element isolation region 56 Plug electrode 511 Interlayer insulating layer 512 Ti layer 513 Lower electrode 514 Ferroelectric layer 515, 517 Pt layer 516 Conductive oxide layer 518 SiO ₂ insulating protective layer 519 Wiring 520 Passivation film 521 Upper electrode

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 21/8247 29/788 29/792 (72) Inventor Tetsuo Fujiwara 1-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture, Japan Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor Yasuhiko Murata 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor, Kazutoshi Higashiyama 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 F term in Hitachi Research Laboratory, Hitachi, Ltd. (reference) 5F001 AA17 AD33 AG30 5F038 AC05 AC15 EZ20 5F083 AD54 FR02 GA02 GA13 JA13 JA14 JA15 JA38 JA39 JA43 JA45 PR23 PR33

Claims (7)

[Claims] 1. A dielectric element comprising a lower electrode formed on a semiconductor substrate, a dielectric layer formed on the lower electrode, and an upper electrode formed on the dielectric layer, wherein the upper electrode is An upper electrode layer formed on a dielectric layer, a conductive oxide layer for preventing hydrogen diffusion having a perovskite structure formed on the upper electrode layer, and a metal layer formed on the conductive oxide layer. Dielectric element. 2. The dielectric device according to claim 1, wherein the conductive oxide layer is made of a SrRuO ₃ conductive oxide. 3. The conductive oxide layer according to claim 1, wherein the conductive oxide layer is LaTiO ₃ , CaCrO ₃ , S
A dielectric element comprising at least one kind of a conductive oxide composed of rCrO ₃ and CaRuO ₃ . 4. The method according to claim 1, wherein the upper electrode layer and the metal layer forming the upper electrode are formed of P
A dielectric element comprising at least one kind of metal consisting of t, Ir and Ru. 5. The method according to claim 1, wherein the dielectric layer comprises (Pb / A) (Zr / Ti) O ₃ (where A is La, Ba, Nb, Ca , One element selected from Sr). 6. The method according to claim 1, wherein the dielectric layer is made of SrBi ₂ Ta _2-x Nb _x O ₉ (x in the formula)
Is a dielectric element comprising 0 to 1). 7. The dielectric layer according to claim 1, wherein the dielectric layer is made of (Ba ₁ -xSr _x ) TiO ₃ (where x is 0 to 0.9). A dielectric element characterized by the above-mentioned.