JPH07509689A - Cubic metal oxide thin film grown epitaxially on silicon - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This application has serial number 07/846.358 (registered on March 5, 1992) U.S. Pat. No. 5,155,6 issued on May 13, 1992, Published as 58.

field of invention FIELD OF THE INVENTION This invention relates generally to crystalline thick films and their growth. For more details, see cubic perovskite or metal oxide thin films with a buffer layer in between. Ru.

Once upon a time, epitaxial thin films were used exclusively in semiconductor technology. Recently, it has also been used in several other technologies.

High-temperature superconductors such as YBa, Cuρ, , (YBCO) are formed into single bonds on a crystal substrate. Semiconductor with the best and maximum reproducibility when grown epitaxially as a crystalline thin film Indicates the characteristics of the body. These high-temperature ceramic superconductors are anisotropic perovskite crystals It has a structure. For example, the lattice parameters of the a-axis and b-axis of YBCO are 0.38 2 nm and 0.388 nm, but the C-axis lattice parameter is 1.168 nm. . Inam et al. S3. ), the Y′BCO electrode is YBa2Cuρ7. , insulation layer, or also discloses superconducting Josephson devices sandwiching semiconducting or normal conducting layers did. All three layers are grown epitaxially with c-axis orientation, i.e. the a-axis is at the film plane. It is perpendicular to.

This method was also applied to ferroelectric materials for memory. I and the inventors are U.S. Patent No. 5, 155,658 and 5,168,420, the YBCO electrode is a ferroelectric layer. , for example, pbzrrT, ρ, (where, (g)αkl, and this r,: shi cubic lattice I explained about the device that holds the (slightly distorted compared to the structure).

The three layers are grown epitaxially together to form a single crystal thin film.

In one embodiment, the YBCO has a c-axis orientation, i.e., the a-axis is perpendicular to the film plane. Then, the underlying YBCO layer is grown directly on the IAAIO7. Ferroelectric notes like this Li takes advantage of the normal conductivity of YBCO electrodes, rather than operating at superconducting temperatures. .

Both superconducting and ferroelectric devices are integrated on silicon substrates in silicon electronic circuits. If they can be combined, they are likely to be more commercially successful. the As a result, the technology of epitaxially grown YBCO on Si was developed. F ork et al. describe such a technique as “strained epitaxial YBa2Cu on s1, Q , high critical current in 4 LIned epimial YBa, Cuρya Onsi), Appli ed Physics Liners, Volume 5 A1990, pp.

No. 1161-1163. This technology was first developed using yttria-stable zirconia ( ffρJ′)x(Zr2′J)1. , , hereafter YSZ) is deposited on a silicon substrate. Then, ■ω is deposited on YS and E.

Although I showed the 5isZ/YBCo/FZT/YE■ structure in my original US patent application, For many important uses, it is not completely worth it. The electrodes are structurally and electronically paired. The upper ■■ electrode is exposed at a temperature too high for the lower IT, which is deposited on the surface. need to grow. Furthermore, recently discovered materials such as EaKbiO, Some high-temperature ceramic superconductors do not have an anisotropic perovskite crystal structure but instead has a cubic or nearly cubic crystal lattice structure. Also, ferroelectric Electrodes for sexual memory do not need to be superconducting regardless of temperature; It is sufficient to show conductivity. Recent research in single-crystal ferroelectric memory has shown that 5rTr O, growing on lanthanum strontium covalley) (La,..., Sr, C A conductive oxide electrode consisting of oO, in the formula 0 (X (1, hereinafter referred to as LSCO) was used.

Cheung et al. Conductive and epitaxial La5rCoO thin film J grown by (Co nductive and epitaxial La5aC thin fi lm grown b凵@pulsed 1aser Deposition as electrcxies for ferroel electric PLZT devices) 1992 3rd year California state Monterey - Disclosed in Abstracts of the 4th International Symposium on Integrated Ferroelectrics, p. 9C. This non- The material that can be grown at a constant low temperature is a crystal of 0382±0.2 nm. It has lattice parameters and can be said to be nominally cubic. Nominally cubic means that the lattice parameter is 5 It means that the crystal lattice axes are perpendicular within 3 degrees and do not differ by more than %. moreover, On a Si substrate, a single crystal layer of a ferroelectric material such as A dielectric material such as lithium (SrTIOJ) must be directly formed. my sutra In our experiments, nominally cubic perovskite was formed on a Y-buffer 31 substrate with high quality epitaxial growth. Unable to achieve critical growth.

Summary of inventions The present invention provides a method for producing crystalline metal oxide thin films on silicon substrates, and It can be summarized as a device that was created. For example, Innotria stable zirconia Which buffer core is grown on silicon and has a C-axis oriented anisotropic Peropus power template? The rate grows into this buffer layer. This template will later grow The cubic metal oxide has highly oriented crystallinity. Cubic metal oxides are Can be used in one of the various parts of layered crystal devices, such as poles or ferroelectrics .

Brief description of the drawing FIG. 1 is a sectional view of a basic embodiment of the invention.

2-4 are cross-sectional views of additional embodiments of the invention.

Detailed description of the invention Anisotropic perovites (also called stratified perovites) are produced under appropriate growth conditions. Therefore, it is considered that the C-axis orientation shows a large growth tendency. Inam et al. Defines a powerful material. This tendency is due to the low level of a-b crystal planes that are not exposed during growth. This seems to be caused by high free energy, but in the a-b plane between ■■ and YSZ. to eliminate the 56% lattice mismatch problem and the C-axis of YBCO on YSz. It is also sufficient to cause oriented growth. In my US patent application, the C-axis oriented YBCO Explain how the layer can be grown on a YSZ puffer layer deposited on silicon. It's clear. YBCO not only functions as an electrode, but also has more than 80% C-axis alignment. It also serves as a template for later growth of the ferroelectric material. On the contrary , the nominally cubic berovskite exhibits a strong tendency for such specific orientation in crystal growth. There is nothing to show. As a result, the nominal cubic berovskite is of high quality on the mulch OJ. A polycrystalline film is formed on YSZ under the growth environment that creates a single-crystal perovskite film. It tends to grow as an incorrect phase, or as an incorrect phase.

Stratified belobskite (or anisotropic perovskite) Provides a template for the ebitaxial growth of cubic perovus I discovered that it does. As shown in Figure 1, Innotria stable zirconia αS Z) is grown on a single crystal silicon substrate l2. ■For 8 to 18 mol%, If it contains about 9 mol% of yttria, it is completely stable. Perfect A stable YSZ is formed with (100) orientation on (100) orientation silicon.

The anisotropic perovskite layer l4 is a growth ring suitable for forming a substantially monocrystalline unidirectional film. 1 layer is deposited under the border. Anisotropic (or layered) berovskite is the nominal It refers to perovskite materials that are not cubic. Technically important anisotropic perob Many of the skites are twice or more long than the a- and b-axis lattice parameters. 1 grid parameter, but the grid cells are approximately rectangular. anisotropic berovska The metal layer l4 is made of a nominally cubic metal oxide (in short, As a template layer for the epitaxial growth of layer 16 of velopskite material) Function. Such a template layer l4 has a well-defined crystal orientation, i.e. This promotes the epitaxial growth of the upper layer with substantially single crystals. Metal oxide ( (in other words, it has both metal ions and oxygen), the ferroelectric lanthanide Conia lead titanate CPb,,,La,Zr,,ρ,, where 0<x<1 and Q< y<1, hereafter p, dielectric strontium titanate (SrTiO;), and and conductive oxide LSCO. As will become clear in the examples below, The metal oxide layer 16 can be incorporated into a number of different devices.

[Example 1]

Anisotropic perovskite is bismuth titanate (BiTiρ,2), cubic metal oxide A structure of Pjigo was grown with x = OJ and y = 0.1 (see Figure 1). B i, Tiρ,, has an orthorhombic crystal structure, and the lattice parameters are 054l, 0.545 , and 3.28 nm. The deposition of this and other examples is based on my other features. It was performed by pulsed laser ablation following the procedure described previously.

Deposition of the YSZ layer on the silicon substrate was performed in a separate system. This process This is explained in the article by Fork et al. cited in the article. Various remaining materials All surfaces to be vapor deposited are placed in a vapor deposition chamber, and the vapor deposition chamber is placed between vapor depositions. I hit the beam without opening the bar. The target surface has the desired stoichiometry excluding oxygen. It was a sintered powder disc.

A 5 nm thick YSZ layer was deposited on a (001) oriented silicon wafer with a 9-molecular thickness. % yttria to stabilize the cubic phase. Template layer is 20 nm f) Bi4Tip, , evaporated at a substrate holder temperature of 640'C for C-axis orientation. I arrived. While depositing a 0.3 μm PL layer to form a cubic metal oxide layer, the substrate holder was The temperature was maintained at -(a)°C. X-ray diffraction shows only the (00m) peak of PLZT. However, this indicates that it has grown to a high degree as a perovskite. 2θ=221 The width of the (001) peak was 0.3° or less. Approximately 35% channeling step When compared with 17% of PL2T grown on a substrate with a crystalline mass of η10, good.

[Comparative example 1] ? A structure similar to that in Example 1 was grown, but here no force was used to grow the template layer. One.

X-ray diffraction shows a perovus power peak < (OOm), and a peak of (111). Only Rubik is shown. Therefore, without the template layer, P and T are perovs not formed as a kite, but instead as a non-ferroelectric pie-mouth crawl .

A second example of the invention is ferroelectric random access memory (FRAM).

A FRAM integrated circuit has an array of memory cells, one of which is shown in cross section in FIG. Shown in the figure. Completely bistable YS2J10 is a silicon wafer with (001) orientation. - The thickness is preferably in the range of 50 to 100 nm.

Thin template preferably made of layered velopskite material with a thickness of 2 to 10 nm The second layer 20 is deposited on top of the second layer ν) under an environment that promotes C-axis orientation growth.

Examples of such drifting materials include ■■, BIβr2Ca. Cu,,ρ, (in the formula n is a non-negative integer), La2,, SrCuOi (0>x>1 in the formula), and and Bi, Tiρ, 2, etc. Other examples are substitution induction from Bi, Tiρ, . Subbarao [ferroelectricity and its hardness in BJψ,2] Condition J (Ferroelectric5 in Br, Tr, O,, an d Its Solid Solutions), Ph 凾東奄MO≠戟@Revi ew, Volume 122, 1961, pp. 804-807.

On the template layer 20, a cubic or nearly cubic conducting perovskite or other A lower electrode layer 22 made of metal oxide is deposited. Examples of such materials in FRAM Examples include Bi, SrRuO,, SrCrO, and SrVO, etc. . A thin ferroelectric layer 24 (preferably PI2T) is deposited on the bottom electrode 22. . For other examples of ferroelectric materials, see my patent application 07/616,166-current Let's explain patent 5,168,420 (issued December 1, 1992) v1 Ru. A top electrode layer 26 is deposited on the ferroelectric layer 24. This upper electrode layer 26 It is desirable that it be made of the same material as the lower 7t pole layer 22.

Two times of masking and enoching create a step-like structure, which is the bottom electrode 2. 2 and can be contacted at the top surface of the lower electrode 22. spin-on glass electrode An insulating layer 30 is formed that isolates 22 and 26, but a contact hole is formed between them. Make it clear. Deposit and define metallization layers to create electrical interconnects 32 and and 34 are formed between electrodes 22 and 24 and other circuitry. This circuit is FR AM gate circuits may include MOS gates formed on silicon substrates. Ru.

[Example 2] The ferroelectric memory was fabricated with a structure similar to that shown in Figure 2, but with minimal lateral definition. ing. As shown in FIG. 3, the YBCO template layer 20 is The film was deposited to a thickness of 20 nm on the substrates 10 and 12, and the substrate holder was 8 nm thick. The temperature was maintained at 10°C. At this temperature, YBCO grew with C-axis orientation. board holder temperature of 11 degrees to 640 degrees Celsius, and the layer W of LSCO with x=0.5 was reduced to a thickness of 100 nm. The lower electrode 22 was formed by making it 4 thorns long. Ferroelectric of PJ with the same composition as the first example The layer 24 was grown at 640° C. to a thickness of 0.3 μm. Upper electrode layer of LSCO was grown in the same manner as the lower electrode layer 20. LSCO than YBCO for electrodes The reason for this advantage is that PLZT is not exposed to high temperatures during the growth of the upper electrode layer. .

A Pt/Au metallization layer was deposited in an array of 100 μm circles 36. Photolithographically defined. After removing the photoresist, the top LSCO layer is 1% Separate upper electrodes 38 are isolated by etching with nitric acid. with mask Rather than performing another etch to make contact with the bottom electrode 20, a very large A large upper electrode 30 was included in the mask pattern.

For electrical testing, connect the electrical leads to the selected small top electrode and large top electrode. The capacitance determined by the polarity of the direct JIJ circuit is determined by the selected small electrode. managed by a capacitor.

The memory elements were electrically tested. For 2■ bipolar pulses, residual polarity ±13.5 μC/CrrI2 was shown. Next, this is done by applying 2 ■ bipolar pulses in 5 ■ seconds. I checked for fatigue. After 2xlO” cycles, the residual polarity is approximately ±11 μacrn2. It was lowered and slightly asymmetrical. This long life has always been a problem for polycrystalline Buddha M. This contrasts sharply with the fatigue of

The present invention can also be applied to integrated optics using electro-optic effects. This electric Pneumo-optic action can be achieved by changing the refractive index of electro-optic materials such as PLZT. , the voltage signal causes a phase shift in the optical signal. ptz'r is cubic pelop It can be sandwiched by cubic metal oxide electrodes.

[Example 3] The electro-optical effect was obtained using a 20 nm thick Bi, Tiρ, template on the YSZ board 10. layer 20, LSCO'It pole layer 22 with a thickness of 100 nm, P layer with a thickness of 300 nm An apparatus (see FIG. (also shown). The metal circular contact 36 consisted of 10 nm squares.

When red light is irradiated onto an optically thin T-circle (at the same time, a voltage of 100Hz between ±5V ), and the reflected light has a refractive index modulated to Δn÷2xlO' at the same frequency. However, the “hysteresis” pattern expected in the electro-optic action of ferroelectrics I followed the instructions.

Another embodiment of the invention, shown in cross-section in FIG. It is a working transistor (FEMFET). This transistor function is standard Similar to a field-acting transistor, but when powered by an active gate signal, the The only difference is that the gate signal remains removed when the Ru. This condition is reversed for gate signals of opposite polarity. Polycrystalline FEMFET is , Integration of rUHV-grown ferroelectric films into non-volatile memories J by Lampe et al. Integration of UHV-grown ferroelecti c fi1m = mountain uo no Shima Shield Geki ≠ Koji Geki ■ 7th International Symposium on Ferroelectric Applications, 1990, 7 ．． Published in the 5th edition.

In this FEMFET), the pm (001) oriented silicon substrate clause is the source It has a well 42 diffused or buried in the substrate surface for the drain and drain. So The thickness of the dielectric layer should be minimized, preferably less than 10 nm, to provide polarity to the ferroelectric property. Reduce the voltage required for A thin template layer 46 is epitaxially deposited on the YSZi. Deposit it manually. Its thickness is preferably 2 to 10 nm. template The materials are Bi, Tiρ1. Good. This is because most ferroelectric materials are a This is because the lattice closely matches Bi, Tiρ, 2 on the -b plane. example For example ptzr or BaTi0. A single crystal ferroelectric layer 48 such as a template The layer was deposited to a thickness of approximately 300 layers. The metal electrode 50 is placed on the ferroelectric layer 46. Deposited. A gate layer on the silicon surface is defined by photolithography, and the gate is used as the source. It was made so that it hardly overlapped with the drain well 42. electrical leads gate layer 48, source and drain wells 42, and the back side of the substrate layer (or p-type It was installed on the layer below the town. This FEMFET is normally in the off state Although operating in enhanced mode, the invention is also applicable in normally on-state impairment mode m. . In this mode, the channel below the weak YSZ layer is of the same type but with the source and drain well 42 to a lower density and doped to the opposite type to the substrate clause. be logged.

The present invention can be applied to various devices as shown in the table. Swanz is , articles evaluating many of these application methods are published in [Electronic Ceramics Topics] σo pics in ElecaicCeramics)rEEETransact ions on Electrical Invention), Volume 25, 1990, described in Tarubuki A 935-987 Ta. Also listed are preferred materials for layered perovskites and cubic metal oxides. Indicated.

All listed here are nominally cubic perovskites. The table shows the activity cubic perobus Not mentioning the electrode material that needs to be inserted between the kite and template There is. This electrode material can be chosen quite freely and can be layered or cubic perovskite. or other metal oxides as long as they are compatible with other materials. Br Tip , it is then possible to use a substitution-induced layered structure. It is Noh.

Dynamic random access memory (DRAM) is the most widespread type of semiconductor memory. It is manufactured very well. Storage elements are capacitors charged to one or two states It is. Instead of FRAM's non-volatile capacitors, DRAM uses Ba, Jr. High charging capacity using non-hysteresis dielectric materials such as Tie, 5rTrOs, etc. capacity makes up for the lack of capacitors. The electrodes that sandwich the dielectric of the capacitor are It is formed from metal oxides such as

Surface acoustic waves (SAWs) can be used to form various devices including filters and delay lines. piezoelectric materials such as hexagonal, quartz, and PLZT used for. 5reenivu and others are pressure! About SAW devices using thin films "Surface acoustic wave propagation on lead titanate thin film" wave propagation on 1ead zirconate Imnate Yama in ■ Amami Pm), Applied Physics Ltner s.

52, 1988, pp. 709-711. Such a thin film In a SAW device, surface acoustic waves are transferred to an interdigital transducer. Therefore, it is placed in a thin film and guided within the thin film.

Integrated optics using electro-optic action has been briefly explained above. PLZT Ferroelectric materials such as ferroelectric materials have very large electro-optic effects. ferroelectric thin film One application of integrated optics that has utilized optical waveguides and associated devices is phase shifters. and Matsuno) and Zehnder modulators. This is according to Kawaguchi et al. [Pji] Thin film waveguide J (PL2 blood n-film waveguides), Aphed 0ptiCs, Volume 23, 1984, pp, 2187419 1, and Mukherjee et al. "Electro-optical behavior in thin-film lanthanum-doped lead zirconate titanate" (Electro-optic effects in thin-film an mountain anum-doped 1ead zirconat■■狽≠shi≠狽■j , 0ptics Liners, Volume 15, 1990, pp, +51-15 3. In a waveguide, the waveguiding medium has a refractive index that is greater than the surrounding area. This is a necessary condition for the primary material. In the case of thin films, perovskite thin films are It must have a refractive index higher than . In the case of a YSZ buffer silicon substrate, The refractive index of YSZ is about 1.75, while the refractive index of perovskite is between 2.35 and 2.75. The range is 7. Therefore, a single optical mode propagates in a 0.2 μm thick film. can be done.

Another electro-optical application is both in the visible and in the 13-1.55 μm range. This is a spatial light modulator for use in Such a device is proposed by “Two-dimensional silicon/ PLZT Spatial Light Modulator: Design Considerations and Techniques” σwo-dimensional 5ilicon/PLZT spa mouth ml Light modulators F design considerations (arid technology), 0pti cal Engineering, Volume 10,000, 1986, pbuki A 250-26 0 disclosure It is. However, current equipment uses silicon evaporated onto polycrystalline PL2T. Manufactured by laser recrystallization. Polycrystalline nature of the image material is undesirable. child These modulators include programmable Fourier plane filtering, optical logic, and Used for latch pad memory, serial/parallel conversion, etc. The spatial light modulator of the present invention is , has a silicon substrate, which contains a photoelectric detector and driver, and a crystal ptzr It includes a thin film and an associated buffer layer grown thereon for the modulator.

Furthermore, other applications include electro-optic intensification with acousto-optic photodetectors and semiconductor lasers. There are also dielectric thin films.

Non-destructive read memories use ferroelectric layers. The first is the FEMFET mentioned above. It is. The second is U.S. Patent 5,051,950 and VTna by Evans et al. ``High-speed non-destructive readout from thin-film ferroelectric memory J (High 5peed, nondestructive readout from in -film ferr shield ■ Gekimomo Takame@memory), Applied Physics Letters, Volume ω, 1992, pp , 3319-3321. In this secondary memory, electrical pulses writes one or two logic states to the ferroelectric capacitor.

However, the stored information is read using electro-optic action, i.e. a laser beam. Being exposed. The polarity state is different depending on what is recorded electrically, so the laser beam The interactions between systems and materials are correspondingly different. Two logical conditions are detected separately. If so, there must be a difference of at least 02'' phase angle between the two.

In pyroelectric materials, the polarity changes in response to temperature changes, and this effect Expressed by coefficient γ. Pyroelectric detectors use thermal or infrared radiation, including imaging Can be used as a detector. PbTi0. , PL2T, and Titano Ferroelectric perovskites, such as acid-lead lanthanum, exhibit excellent pyroelectric properties . Takayama et al. modified the N-axis orientation of PbTi0. Pyroelectric red made of thin film Preparation and characteristics of external wire sensor teristicsof pyroelectric 1nfrared 5e nsors made of c-axis oriented La-mod 奄■奄■п@PbTi0. output infi1ms), Journal of Appl ied Physics, Vol. 61, 1987, pp. 411-415. An electric thin film detector was disclosed. Thin film pyroelectricity integrated into imager and provide the ability to combine with silicon peripheral circuitry. Pyroelectric ferroelectric material If a strong crystal orientation is produced by pitaxial growth, the need for boring may be reduced. It is possible to obtain very large pyroelectric signals.

Additionally, highly absorbing electrodes such as YBCO and LSCO provide a blackbody structure.

Smart materials, including integrated actuators and sensors, can be learned from experience. be.

Newham et al. “Smart electronic ceramics J (SmanE1ec+ro ceramics), Journal of the American Ceramics) amics 5ociety, Volume 74, 1991, pp, 463-479 has published a critical article. Simply stated, these materials and devices are In order to continuously change the condition of materials and equipment in response to external stimuli that change rapidly. Use a feedback circuit for this purpose. Therefore, these materials respond to external stimuli. It can be said that this is a special sensor. This stimulation can be electrical, chemical, mechanical, or optical. It can be physical, magnetic, or thermal. Until now, these sensors Integration into control networks using hybrid multichip modules It has been. Lattice and scientific studies on perovskite smart materials like PLZT The use of oxidized electrodes that meet the requirements for smart materials, resistors, capacitors, and interconnects It offers great advantages in integration on one chip.

In most embodiments, only the second buffer layer of the device is grown on the template layer. However, due to its characteristics, it can be integrated into equipment. An example of this is A non-volatile memory described in the original patent, evaporated directly onto ittria-buffered silicon. It has YBCO/PZT/YBω. Among the examples, YS ZIii is epitaxial to silicon, whereas YsZ is epitaxial to silicon. is known to provide a template for crystal growth even when grown on There is. The present invention uses other template materials such as sapphire and CeO2. , it is also possible to promote C-axis growth of anisotropic perovskites. In the example, Although the structures were formed by laser laser ablation, other methods, e.g. It is also possible to use methods such as chemical vapor deposition and molecular beam epitaxy. .

The templates of the present invention allow the production of desired crystals of various technologically important oxides. can be grown in any state. Depending on its application, the intermediate layer material ( e.g. LSCO for YBCO) can be widely selected and at lower temperatures processing and an easier-to-use interface. Also the present invention is a possible epitaxial heterostructure of two materials with very different lattice constants. It also provides sex.

Figure 1 Figure 2 Figure 3 Figure 4 Continuation of front page (51) Int, C1, 6 identification code Office reference number HOIG 4/33 HOIL 21/8242 37102 9353-4M 39102 B 9276-4M 39/24 B 9276-4M 9174-5E (81) Designated countries EP (AT, BE, CH, DE.

DK, ES, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE) , C.A., J.P. I HOIG 4106 102

Claims (1)

[Claims] Claim 1: A silicon/metal oxide heterostructure consisting of: silicon. substrate; a buffer layer formed on the silicon substrate; an anisotropic layer formed on the buffer layer; A tensile layer made of perovskite. the template layer is formed substantially c-axis oriented; and the template layer is formed on the template shoulder. Nominally cubic metal oxide layer. 2. The heterostructure of claim 1, wherein the buffer layer is yttria-stabilized zirconia. consisting of a. 3. The heterostructure of claim 1, wherein the metal oxide layer is conductive and substantially monocrystalline. crystal, forming a lower electrode, and further comprising: on the metal oxide layer. a substantially single crystal ferroelectric layer formed on the ferroelectric layer; and a second substantially single crystal ferroelectric layer formed on the ferroelectric layer. Conductive metal oxide layer. Claim 4 The heterostructure of claim 3, wherein the second metal oxide layer is substantially single crystal; The two metal oxide layers are made of the same metal oxide. 5. The heterostructure according to claim 1, wherein the cubic metal oxide layer comprises a ferroelectric layer. thing. 6. The heterostructure of claim 5, wherein the silicon substrate is located between the metal oxide layers. a first conductive region under the metal oxide layer, and a second conductive region under the end portions of the metal oxide layer. consisting of conductive areas. Claim 7: The heterostructure according to claim 1, wherein the cubic metal oxide layer is a piezoelectric layer. . 8. The heterostructure according to claim 1, wherein the cubic metal oxide layer comprises an electro-optic layer. thing. 9. The heterostructure of claim 1, wherein the cubic metal oxide layer is pyroelectric. thing. 10. The heterostructure of claim 1, wherein the template layer is made of bismuth titanate. consisting of 11. A ferroelectric memory element comprising: a single crystal silicon base. Board; Buffer layer formed on the substrate: A single crystal film made of a conductive metal oxide formed on the buffer layer. a layer that facilitates the formation of the metal oxide as the single crystal film; and A ferroelectric layer formed epitaxially on a crystal film. 12. The ferroelectric memory element of claim 11, wherein at least one of the ferroelectric layers comprises: 80% is c-axis oriented. Claim 13: A method of forming a silicon/metal oxide heterostructure, comprising the steps of: What is: depositing a first layer of buffer material on the crystalline silicon substrate; Anisotropic perovskites under growth conditions that favor c-axis oriented growth of anisotropic perovskites. evaporating a second layer of light, the buffer material substantially including the second layer of to encourage growth as a crystalline layer; and a nominal cubic metal acid on said second layer. Depositing a third layer of oxide. 14. The method of claim 13, wherein the buffer material comprises yttria stabilized zirconia. consisting of a. 15. The method of claim 13, wherein the growth conditions include maintaining the first layer at a first temperature. Further, a substantially crystalline fourth layer made of ferroelectric material is vapor-deposited on the second layer. The first, second, and third layers are maintained at a second temperature lower than the first temperature. 16. The heterostructure of claim 4, wherein the same metal oxide is lanthanum stron. Consisting of tiumcoparate. 17. The heterostructure of claim 4, wherein the same metal oxide is formed from SrRuO3. What will become.