Elastic wave device, communication device, and manufacturing method

Abstract

Since an IDT electrode is fine, it is necessary to improve power resistance to migration. The present invention is provided with: a piezoelectric layer; an electrode provided on the piezoelectric layer; and a covering part that covers at least a portion of the side surface of the electrode and contains an element constituting the piezoelectric layer other than oxygen and nitrogen.

Description

Technical Field

[0001] The present disclosure relates to elastic wave devices. Background Art

[0002] In an elastic wave device, an IDT electrode is formed of an aluminum film on a piezoelectric substrate.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-078384 Summary of the invention

[0006] According to one embodiment of the present disclosure, there is a piezoelectric layer; an electrode provided on the piezoelectric layer; and a covering portion covering at least a portion of a side surface of the electrode; the covering portion contains an element other than oxygen and nitrogen constituting the piezoelectric layer.

[0007] According to another aspect of the present disclosure, the method includes the steps of: forming a piezoelectric layer; forming an electrode on the piezoelectric layer; and dry-etching the piezoelectric layer and the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. 1 is a schematic diagram showing a cross-sectional structure of the elastic wave device according to the first embodiment.

[0009] Figure 2 This is a diagram that compares the elastic wave device of the comparative example and the elastic wave device of the first embodiment side by side.

[0010] Figure 3 Yes Figure 1 The elastic wave device described herein has a protective film formed thereon.

[0011] Figure 4 FIG. 1 is an example of a cross-sectional structure of the elastic wave device according to the first embodiment.

[0012] Figure 5 Yes Figure 4 A magnified photo of a portion of the.

[0013] Figure 6 Yes means Figure 5 A graph showing the composition of tantalum on a specific line segment in FIG.

[0014] Figure 7 The figures show the results of comparison of the power withstand capability when dry etching was performed and when dry etching was not performed.

[0015] Figure 8 It is a schematic diagram showing the cross-sectional structure of the elastic wave device according to the second embodiment.

[0016] Fig. 9 This is a diagram illustrating a schematic configuration of a communication device in a third embodiment.

[0017] Fig.10 It is a schematic diagram showing the cross-sectional structure of an elastic wave device. DETAILED DESCRIPTION

[0018] Since the IDT electrode is fine, the power resistance due to electromigration is low. In addition, in order to improve the power resistance due to electromigration, when adding a step of forming a covering portion covering the side of the IDT electrode, multiple steps need to be added to the manufacturing process, which increases the manufacturing cost.

[0019] [Implementation Method 1]

[0020] (Board Wave)

[0021] The elastic wave device, for example, excites plate waves. Alternatively, the elastic wave device may also excite body waves. Plate waves are classified into Lamb waves, whose vibration plane is perpendicular to the plate surface; and SH waves, whose vibration plane is parallel to the plate surface. Lamb waves are classified into S mode, which is a symmetric mode, and A mode, which is an antisymmetric mode. The A1 mode corresponds to a first-order antisymmetric mode. In the present embodiment, an elastic wave device using an A1 mode Lamb wave is described, but it is not limited to this. For example, it may be an elastic wave device using a body wave in a thickness shear mode. In the case of a change in the thickness of the piezoelectric layer 3 described later, the resonance characteristics of the plate wave vary greatly among various waves. In the case of a change in the thickness of the piezoelectric layer 3 described later, the resonance characteristics of the body wave also vary greatly.

[0022] An example of a cross-sectional structure of an elastic wave device will be described. Fig. 9 1 is a schematic diagram showing a cross-sectional structure of elastic wave device 100. Elastic wave device 100 is configured by laminating supporting substrate 2, multilayer film 6, piezoelectric layer 3, and electrode 4 in this order.

[0023] The support substrate 2 is a substrate that supports the piezoelectric layer 3 and the electrode 4. The support substrate 2 may be made of silicon, or various materials such as sapphire and glass may be used.

[0024] The multilayer film 6 is an acoustic reflection film formed by alternately stacking a plurality of low acoustic impedance layers 6a and high acoustic impedance layers 6b. Fig. 9 In the embodiment, the low acoustic impedance layer 6a and the high acoustic impedance layer 6b are alternately stacked in four layers. That is, the multilayer film 6 reflects the Lamb wave propagating from the top of the elastic wave device 100 at the interface between the low acoustic impedance layer 6a and the high acoustic impedance layer 6b. In addition, the low acoustic impedance layer 6a may contain SiO2. The high acoustic impedance layer 6b may contain at least one of HfO2, Ta2O5 and ZrO2, for example, HfO2. The multilayer film 6 may not be present.

[0025] The piezoelectric layer 3 is formed relatively thin. The thickness W of the piezoelectric layer 3 can be less than one wavelength of the plate wave excited by the electrode 4, which is determined by the spacing of the electrodes 4 described later. The piezoelectric layer 3 is made of lithium tantalate, lithium niobate or crystal. In addition, the piezoelectric layer 3 is not limited thereto, and various piezoelectric materials can be used. In the following description, the piezoelectric layer 3 is described as lithium tantalate.

[0026] The electrode 4 is a comb-shaped IDT (interdigital transducer) electrode, that is, a plurality of electrode fingers are formed. In addition, the piezoelectric layer 3 is exposed in the portion where the electrode 4 is not formed. The wavelength of the plate wave excited by the piezoelectric layer 3 is determined by the spacing of the IDT electrodes. The electrode 4 is aluminum, copper, or an alloy thereof.

[0027] Furthermore, the piezoelectric layer 3 may be configured so that a plate wave is excited in the piezoelectric layer 3 by applying an alternating current to the electrodes 4 .

[0028] (Composition of Comparative Example)

[0029] In the elastic wave device 100 of the comparative example, Fig. 9 As shown, the surface of the piezoelectric layer 3 is substantially consistent with the interface between the piezoelectric layer 3 and the electrode 4. That is, the electrode 4 is formed on the piezoelectric layer 3, and no etching or the like is performed thereafter.

[0030] (Overview of frequency characteristics adjustment method)

[0031] In elastic wave device 100 of the comparative example, the thickness of piezoelectric layer 3 and / or electrode 4 varies depending on the position of support substrate 2. Support substrate 2 is, for example, a silicon wafer. Therefore, elastic wave device 100 has different frequency characteristics depending on the position of support substrate 2.

[0032] In order to adjust the frequency characteristics of elastic wave device 100 , the thickness of piezoelectric layer 3 and electrode 4 can be adjusted by cutting by etching or the like.

[0033] (Overview of Elastic Wave Device 1)

[0034] In the elastic wave device 1 according to the first embodiment, dry etching is performed at different thicknesses for each element or each portion of an element of each elastic wave device based on the thickness measured in advance. Figure 1 Schematic diagram showing the cross-sectional structure of the elastic wave device 1 according to the first embodiment. Figure 2 FIG. 1 is a diagram showing the elastic wave devices 100 and 1 according to the comparative example and the first embodiment, and comparing them.

[0035] like Figure 2As shown, in the elastic wave device 1, the piezoelectric layer 3 and the electrode 4 are thinner than those in the elastic wave device 100. Therefore, the elastic wave device 1 is adjusted to obtain the desired frequency characteristics, and the frequency characteristics are improved. Figure 3 FIG. 2 is an example of a cross-sectional structure of the elastic wave device 1 according to the first embodiment. Figure 3 In the present invention, SEM (scanning electron microscope) was used as an imaging method.

[0036] In particular, at the surface of the piezoelectric layer 3 and the interface between the piezoelectric layer 3 and the electrode 4 where the electrode 4 is located, the region where the surface of the piezoelectric layer 3 is exposed is thinner, and the difference in thickness is 50 nm or less. That is, the thickness of the region where the electrode 4 is exposed in the piezoelectric layer 3 is greater than the thickness of the region where the surface of the piezoelectric layer 3 is exposed, and the difference in thickness between the region where the electrode 4 is exposed and the region where the surface of the piezoelectric layer 3 is exposed is 50 nm or less.

[0037] In addition, if Figure 2 As shown in FIG. 4 , it can be seen that the edge of the end of the electrode 4 is cut off by dry etching, and chamfered at reference numeral 43. This can achieve an effect of reducing stress migration caused by vibration of the electrode 4.

[0038] (Formation of Covering Part 5)

[0039] In addition, the elastic wave device 1 includes a cover 5 that covers at least a portion of the side surface of the electrode 4 . The cover 5 is a portion that does not exist in the elastic wave device 100 . Here, the support substrate 2 supports the piezoelectric layer 3 , the electrode 4 , and the cover 5 .

[0040] The thickness of the thickest part of the covering portion 5 is 3 nm or more. In addition, the covering portion 5 includes: a first portion 51; and a second portion, which is located above the electrode 4 compared to the first portion 51 and is thinner than the first portion. That is, the covering portion 5 does not have the same thickness, and the covering portion 5 has different thicknesses in the first portion 51 and the second portion 52. In addition, the covering portion 5 may become thinner toward the upper side of the electrode 4.

[0041] The side surface of the electrode 4 has a first surface 41 which is not perpendicular to the surface of the piezoelectric layer 3. The first surface is located above the electrode 4. The cover 5 is also in contact with the first surface.

[0042] Furthermore, the side surface of the electrode 4 has a second surface 42 near the surface of the piezoelectric layer 3 , which is closer to perpendicular to the surface of the piezoelectric layer 3 than the first surface 41 . The first surface and the second surface are continuous, and the cover portion is also in contact with the second surface 42 .

[0043] Here, the first surface 41 includes the second portion 52, and the second surface 42 includes the first portion 51. That is, the angle formed by the direction perpendicular to the surface of the piezoelectric layer 3 and the second surface 42 is smaller than the angle formed by the direction perpendicular to the surface of the piezoelectric layer 3 and the first surface 41. Therefore, in the second surface 42, the thickness of the covering portion 5 tends to increase.

[0044] By making the first surface 41 inclined relative to the surface of the piezoelectric layer 3, the contact area between the electrode 4 and the covering portion 5 is increased. As a result, the formation of hillocks (protrusions) on the surface of the electrode 4 can be reduced, and the effect of improving the power resistance to electromigration can be obtained. In addition, since the second surface 42 is nearly vertical relative to the surface of the piezoelectric layer 3, the accumulation amount of the covering portion 5 becomes larger. Therefore, when a protective film covering the piezoelectric layer 3 and the electrode 4 is made, the coverage of the protective film near the second surface 42 becomes better, and the effect of reducing electrocorrosion can be obtained.

[0045] Figure 3 Yes Figure 1 The elastic wave device 1 described above is formed with a protective film 7. The protective film 7 covers the piezoelectric layer 3 and at least a portion of the electrode 4. Specifically, the protective film 7 covers the lower side of the electrode 4, that is, the portion of the electrode 4 close to the piezoelectric layer 3, via the first portion 51. The protective film 7 can be made of various materials such as SiO2, SiN, SiON, AlN, ZrO2, Ta2O5, ZnO, Al2O3, and HfO2, for example, SiO2, SiN, AlN, Ta2O5, etc.

[0046] (Composition of Covering Section 5)

[0047] In such Figure 3 In the SEM image shown, it is highly likely that the piezoelectric layer 3 and the cover 5 have similar compositions. This is thought to be due to redeposition of the portion scraped off by dry etching. In other words, it is thought that the electrode 4 is covered by the cover 5 .

[0048] Next, in order to analyze the composition of the covering portion 5 in detail, Figure 4 Yes Figure 3 A part of the photograph (reference numeral 8) is enlarged. Figure 5 Yes Figure 4 The tantalum composition amount on the line segment indicated by reference numeral 9 in FIG. 1 is measured.

[0049] like Figure 5 As shown in the lower side of FIG. 1 , the measured value of the tantalum composition amount becomes larger between 60nm and 80nm. That is, it is known that the tantalum element is contained in this interval of the cover 5. In fact, in this interval and the corresponding Figure 5 On the upper side, the concentration changes and the composition changes, so it is believed that tantalum is measured.

[0050] According to the composition of the piezoelectric layer 3, it is considered that the electrode 4 is covered. When the piezoelectric layer 3 is lithium tantalate, lithium or tantalum may be contained as an element constituting the covering portion 5. When the piezoelectric layer 3 is lithium niobate, lithium or niobium may be contained as an element constituting the covering portion 5. When the piezoelectric layer 3 is crystal, silicon may be contained as an element constituting the covering portion 5. When the piezoelectric layer 3 is other piezoelectric materials, the covering portion 5 may also contain various elements contained in the piezoelectric material. The various elements are, for example, metal elements. That is, the covering portion 5 contains elements constituting the piezoelectric layer 3 other than oxygen and nitrogen. In this description, as long as the covering portion 5 contains an element different from oxygen and nitrogen among the elements constituting the piezoelectric layer 3, it does not deny that the covering portion 5 contains oxygen and nitrogen.

[0051] When the piezoelectric layer 3 is made of lithium tantalate, the covering portion 5 may be made of lithium tantalate, that is, tantalum oxide. When the piezoelectric layer 3 is made of lithium niobate, the covering portion 5 may be made of lithium niobate, that is, niobium oxide.

[0052] (Improvement in power handling)

[0053] Figure 6 The results are a comparison of the withstand power when dry etching was performed and when dry etching was not performed. That is, the case where dry etching was performed was the case where the elastic wave device 1 was tested, and the case where dry etching was not performed was the case where the elastic wave device 100 was tested. In addition, the test was performed by measuring the following two types of measurements: the measurement of the destructive power of the element of the elastic wave device 1 or 100 and the measurement of the migration power that starts to cause electromigration in the electrode 4.

[0054] like Figure 6 As shown in FIG. 1 , the destruction power and the migration power increase by performing dry etching. In other words, it is known that the power withstand is improved by dry etching.

[0055] This is considered to be an effect of the coating 5 covering the electrode 4. That is, the electrode 4 is coated with tantalum or niobium, etc., which are elements with higher density than aluminum constituting the electrode 4, so that electromigration is less likely to occur.

[0056] In addition, the insulation distance is also increased by covering the electrode 4 with the covering portion 5. Furthermore, the possibility of forming hillocks is reduced by covering the electrode 4 with the covering portion 5.

[0057] Furthermore, the difference in the tilt angles of the first surface 41 and the second surface 42 with respect to the piezoelectric layer 3 can adjust the amount of deposited cover 5 or the area in contact with cover 5. As a result, electromigration is less likely to occur.

[0058] (Manufacturing method)

[0059] The elastic wave device 1 is manufactured by the following steps: First, the piezoelectric layer 3 is formed on the supporting substrate 2. Furthermore, an aluminum film is formed on the piezoelectric layer 3, and the aluminum film is etched using a photoresist mask to form the electrode 4.

[0060] Then, the thickness of the piezoelectric layer 3 and the electrode 4 is measured by various thickness measurement methods. This is to calculate the extent of etching required to obtain the elastic wave device 1 having the frequency characteristics matching the desired values.

[0061] Based on the measured thickness, the etching amount for obtaining the desired frequency characteristics is calculated, and the piezoelectric layer 3 and the electrode 4 are dry-etched with the etching amount different for each element to obtain the elastic wave device 1. Here, the material separated from the piezoelectric layer 3 by dry etching is attached to at least a part of the side surface of the electrode 4, thereby forming the covering portion 5. In other words, by performing dry etching, the covering portion 5 that improves the power resistance can be formed while adjusting the thickness of the piezoelectric layer 3 to obtain the desired frequency characteristics. Therefore, it is the minimum process that is fundamentally required to obtain the desired frequency characteristics, and there is no need to add multiple processes to the manufacturing process.

[0062] [Implementation Method 2]

[0063] Figure 7 Schematic diagram showing the cross-sectional structure of an elastic wave device 1a according to Embodiment 2. Elastic wave device 1a differs from elastic wave device 1 in that a portion of electrode 4 is buried in piezoelectric layer 3. In addition, dry etching is performed in the same manner as in Embodiment 1, thereby forming a cover 5.

[0064] Therefore, the electrode 4 is covered by the piezoelectric layer 3 at the buried portion except the cover portion 5, that is, the electrode 4 is covered by an element having a higher density than aluminum, such as tantalum or niobium. As a result, the electrode 4 is less likely to undergo electromigration, and the power resistance is improved.

[0065] [Implementation Method 3]

[0066] Figure 8 This is a diagram illustrating a schematic structure of a communication device 151 in the third embodiment. The communication device 151 is an application example of an elastic wave device of one mode of the present disclosure, and performs wireless communication using radio waves. The communication device 151 may include a splitter 101 as a transmission filter 109 and another splitter 101 as a reception filter 111. The two splitters 101 may each include an elastic wave device of one mode of the present disclosure. The elastic wave device may be an elastic wave device 1 or an elastic wave device 1a. In this way, the communication device 151 may include an elastic wave device of one mode of the present disclosure.

[0067] In the communication device 151, the transmission information signal TIS containing the information to be transmitted can be modulated and frequency-boosted by the RF-IC (Radio Frequency-Integrated Circuit) 153 and converted into a transmission signal TS. The modulation and frequency boosting can be converted into a high-frequency signal having a carrier frequency. The bandpass filter 155 can remove unnecessary components other than the passband for transmission from the TS. Then, the TS after removing the unnecessary components can be amplified by the amplifier 157 and input to the transmission filter 109.

[0068] The transmission filter 109 can remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 109 can output the TS after removing the unnecessary components to the antenna 159 via the antenna terminal. The antenna terminal can be, for example, the above-mentioned TCin. The antenna 159 can convert the electrical signal TS input to itself into a wireless signal, that is, an electric wave, and transmit the electric wave to the outside of the communication device 151.

[0069] In addition, the antenna 159 can convert the received radio waves from the outside into an electric signal, i.e., a received signal RS, and input the RS to the receiving filter 111 via the antenna terminal. The receiving filter 111 can remove the unnecessary components outside the passband for reception from the input RS. The receiving filter 111 can output the received signal RS after the unnecessary components are removed to the amplifier 161. The output RS can be amplified by the amplifier 161. The bandpass filter 163 can remove the unnecessary components outside the passband for reception from the amplified RS. The RS after the unnecessary components are removed can be frequency-reduced and demodulated by the RF-IC 153 and converted into a received information signal RIS.

[0070] TIS and RIS can be low frequency signals (baseband signals) containing appropriate information. For example, TIS and RIS can be analog audio signals, or they can also be digitized audio signals. The passband of the wireless signal can be appropriately set in accordance with various well-known standards.

[0071] 〔Summarize〕

[0072] An elastic wave device according to a first aspect of the present disclosure includes: a piezoelectric layer; an electrode provided on the piezoelectric layer; and a covering portion covering at least a portion of a side surface of the electrode and containing an element constituting the piezoelectric layer other than oxygen and nitrogen.

[0073] According to the above configuration, the possibility of electromigration of the electrode can be reduced by the covering portion, and the power handling capacity of the elastic wave device can be improved.

[0074] In the elastic wave device according to aspect 2 of the present disclosure, in aspect 1, the piezoelectric layer may contain lithium tantalate, and the element may be lithium or tantalum.

[0075] In the elastic wave device according to aspect 3 of the present disclosure, in the aspect 1, the piezoelectric layer may contain lithium niobate, and the element may be lithium or niobium.

[0076] In the elastic wave device according to a fourth aspect of the present disclosure, in the first aspect, the piezoelectric layer may include crystal, and the element may be silicon.

[0077] According to the above configuration, the covering portion includes a part of the element constituting the piezoelectric layer. Therefore, the constituent element of the piezoelectric layer redeposited by dry etching covers the electrode.

[0078] In the elastic wave device according to aspect 5 of the present disclosure, in aspect 1 or 2, the piezoelectric layer may be lithium tantalate, and the covering portion may contain tantalum oxide.

[0079] In the elastic wave device according to aspect 6 of the present disclosure, in the aspect 1 or 3, the piezoelectric layer may be lithium niobate, and the covering portion may contain niobium oxide.

[0080] According to the above configuration, the covering portion contains a compound of elements constituting the piezoelectric layer. Therefore, the compound related to the piezoelectric layer redeposited by dry etching covers the electrode.

[0081] In an elastic wave device according to a seventh aspect of the present disclosure, in any one of aspects 1 to 6, a density of the covering portion may be greater than a density of the electrodes.

[0082] According to the above configuration, since the electrode is covered with the covering portion composed of an element having a higher density than the electrode, electromigration of the electrode can be prevented.

[0083] In an elastic wave device according to an eighth aspect of the present disclosure, in any one of the first to seventh aspects, a thickness of the thickest portion of the covering portion may be 3 nm or more.

[0084] According to the above configuration, the thickness of the covering portion can be set to 3 nm or more, and the electrode can be covered with a sufficient thickness of the covering portion. Therefore, the power handling capacity of the elastic wave device can be improved.

[0085] In an elastic wave device according to aspect 9 of the present disclosure, in any one of aspects 1 to 8, the cover may include: a first portion; and a second portion that is located above the electrode relative to the first portion and is thinner than the first portion.

[0086] According to the above configuration, the cover portion can be thicker on the piezoelectric layer side.

[0087] The elastic wave device of mode 10 of the present disclosure may have, in any of modes 1 to 9, a protective film covering the piezoelectric layer and at least a portion of the electrode; the protective film may cover a portion of the electrode close to the piezoelectric layer via a first portion.

[0088] According to the above configuration, the coverage of the protective film in the vicinity of the lower side of the electrode becomes better, and the effect of reducing the electric corrosion can be obtained.

[0089] In the elastic wave device according to aspect 11 of the present disclosure, in any one of aspects 1 to 10, the side surface of the electrode may have a first surface that is not perpendicular to the surface of the piezoelectric layer; and the cover portion may be in contact with the first surface.

[0090] According to the above configuration, the side surface of the electrode can include a first surface that is not perpendicular to the surface of the piezoelectric layer. Therefore, the contact area between the electrode and the covering portion can be increased.

[0091] In the elastic wave device of mode 12 of the present disclosure in mode 11, the side surface of the electrode may also have: a second surface, located near the surface of the piezoelectric layer and continuous with the first surface; an angle formed by a direction perpendicular to the surface of the piezoelectric layer and the second surface is smaller than an angle formed by the perpendicular direction and the first surface; and the covering portion is in contact with the second surface.

[0092] According to the above configuration, the side surface of the electrode can have a second surface that is closer to perpendicular to the first surface than the first surface near the surface of the piezoelectric layer. Therefore, the amount of deposited covering portions can be increased on the second surface.

[0093] In an elastic wave device according to aspect 13 of the present disclosure, in any one of aspects 1 to 12, a thickness of a region of the piezoelectric layer where the electrode is located may be greater than a thickness of a region of the piezoelectric layer where the surface thereof is exposed.

[0094] According to the above configuration, the thickness of the piezoelectric layer can be made thinner in the region where the surface of the piezoelectric layer is exposed than in the region where the electrodes overlap. That is, the piezoelectric layer can also be dry-etched together with the electrodes, making processing easy.

[0095] In an elastic wave device according to a fourteenth aspect of the present disclosure, in any one of the first to thirteenth aspects, a difference between a thickness of a region of the electrode and a thickness of a region of the surface where the piezoelectric layer is exposed may be 50 nm or less.

[0096] According to the above configuration, the difference between the thickness of the piezoelectric layer in the region where the electrodes overlap and the thickness of the piezoelectric layer in the region where the surface of the piezoelectric layer is exposed can be set to 50 nm or less.

[0097] The elastic wave device of mode 15 of the present disclosure may further include, in any one of modes 1 to 14,: a supporting substrate supporting the piezoelectric layer, the electrode and the covering portion; the electrode being an electrode finger; the thickness of the piezoelectric layer being less than 1 wavelength determined by the spacing between the electrode fingers; and the piezoelectric layer being configured as an excitation plate wave.

[0098] According to the above configuration, the elastic wave device can be configured so as to function as an elastic wave device.

[0099] An elastic wave device according to a sixteenth aspect of the present disclosure is capable of exciting waves in any one of the first to fourteenth aspects.

[0100] An elastic wave device according to a seventeenth aspect of the present disclosure is capable of exciting a body wave in any one of the first to fourteenth aspects.

[0101] A communication device according to aspect 18 of the present disclosure may include the elastic wave device described in any one of aspects 1 to 17.

[0102] The manufacturing method of mode 19 of the present disclosure includes the following steps: forming a piezoelectric layer; forming an electrode on the piezoelectric layer; and dry etching the piezoelectric layer and the electrode so that the material detached from the piezoelectric layer by the dry etching adheres to at least a portion of the side surface of the electrode.

[0103] [Notes]

[0104] The invention of the present disclosure is described above based on the drawings and embodiments. However, the invention of the present disclosure is not limited to the above-mentioned embodiments. That is, the invention of the present disclosure can be variously modified within the scope shown in the present disclosure, and the embodiments obtained by appropriately combining the technical means respectively disclosed in different embodiments are also included in the technical scope of the invention of the present disclosure. In other words, it should be noted that those skilled in the art can easily make various changes or modifications based on the present disclosure. In addition, it should be noted that these changes or modifications are also included in the scope of the present disclosure.

[0105] Description of Reference Numerals

[0106] 1.100 Elastic Wave Device

[0107] 2 Support base plate

[0108] 3 Piezoelectric layer

[0109] 4 Electrodes

[0110] 5 Covering

[0111] 6 Multilayer film

[0112] 6a Low acoustic impedance layer

[0113] 6b High acoustic impedance layer

[0114] 7. Protective film

[0115] 41 Page 1

[0116] 42 Side 2

[0117] 51 Part 1

[0118] 52 Part II.

Claims

1. An elastic wave device having: Piezoelectric layer; an electrode disposed on the piezoelectric layer; and The covering portion covers at least a portion of the side surface of the electrode and contains elements constituting the piezoelectric layer other than oxygen and nitrogen. 2 . The elastic wave device according to claim 1 , wherein the piezoelectric layer contains lithium tantalate, and the element is lithium or tantalum. 3 . The elastic wave device according to claim 1 , wherein the piezoelectric layer contains lithium niobate, and the element is lithium or niobium. 4 . The elastic wave device according to claim 1 , wherein the piezoelectric layer contains crystal, and the element is silicon. 5 . The elastic wave device according to claim 1 , wherein the piezoelectric layer is lithium tantalate, and the covering portion contains tantalum oxide. 6 . The elastic wave device according to claim 1 , wherein the piezoelectric layer is lithium niobate, and the covering portion contains niobium oxide. 7 . The elastic wave device according to claim 1 , wherein a density of the covering portion is greater than a density of the electrodes. 8 . The elastic wave device according to claim 1 , wherein a thickness of the thickest portion of the coating portion is 3 nm or more. 9 . The elastic wave device according to claim 1 , wherein the covering portion includes: a first portion; and a second portion that is located above the electrode relative to the first portion and is thinner than the first portion.

10. The elastic wave device according to any one of claims 1 to 9, comprising: a protective film covering the piezoelectric layer and at least a portion of the electrode; The protective film covers a portion of the electrode close to the piezoelectric layer via the first portion.

11. The elastic wave device according to any one of claims 1 to 10, wherein the side surface of the electrode comprises: a first surface that is not perpendicular to the surface of the piezoelectric layer; The covering portion is in contact with the first surface.

12. The elastic wave device according to claim 11, wherein the side surface of the electrode further comprises: a second surface located near the surface of the piezoelectric layer and continuous with the first surface; an angle formed between a direction perpendicular to the surface of the piezoelectric layer and the second surface is smaller than an angle formed between the perpendicular direction and the first surface; The covering portion is in contact with the second surface. 13 . The elastic wave device according to claim 1 , wherein a thickness of a region of the piezoelectric layer where the electrode is located is greater than a thickness of a region of the piezoelectric layer where a surface of the piezoelectric layer is exposed. 14 . The elastic wave device according to claim 1 , wherein a difference between a thickness of a region of the electrode and a thickness of a region where the surface of the piezoelectric layer is exposed is 50 nm or less.

15. The elastic wave device according to any one of claims 1 to 14, further comprising: a supporting substrate supporting the piezoelectric layer, the electrode, and the cover; The electrodes are electrode fingers; The thickness of the piezoelectric layer is less than one wavelength determined by the pitch of the electrode fingers; The piezoelectric layer is configured to excite a plate wave. 16 . The elastic wave device according to claim 1 , which excites waves. 17 . The elastic wave device according to claim 1 , which excites body waves.

18. A communication device comprising: the elastic wave device according to any one of claims 1 to 15.

19. A manufacturing method comprising the following steps: forming a piezoelectric layer; forming an electrode on the piezoelectric layer; and, The piezoelectric layer and the electrode are dry-etched, so that a material separated from the piezoelectric layer by the dry-etching is attached to at least a portion of a side surface of the electrode.

Images