WO2017187724A1 - Elastic wave device - Google Patents

Elastic wave device Download PDF

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Publication number
WO2017187724A1
WO2017187724A1 PCT/JP2017/005730 JP2017005730W WO2017187724A1 WO 2017187724 A1 WO2017187724 A1 WO 2017187724A1 JP 2017005730 W JP2017005730 W JP 2017005730W WO 2017187724 A1 WO2017187724 A1 WO 2017187724A1
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sound velocity
low sound
elastic wave
material layer
wave device
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PCT/JP2017/005730
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French (fr)
Japanese (ja)
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克也 大門
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株式会社村田製作所
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Publication of WO2017187724A1 publication Critical patent/WO2017187724A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves

Definitions

  • the present invention relates to an elastic wave device using a piston mode.
  • Patent Document 1 discloses an elastic wave device using a piston mode.
  • an IDT electrode, a dielectric layer, a dielectric material layer for forming an edge region as a low sound velocity portion, and a protective film are laminated in this order on a piezoelectric substrate.
  • the dielectric material layer is provided above one electrode finger of the IDT electrode and the tip portion of the other electrode finger.
  • a central region located in the center of the electrode fingers in the extending direction and edge regions arranged on both sides of the central region are provided.
  • the intersecting region is a region where an electrode finger connected to one potential and an electrode finger connected to the other potential overlap when viewed in the elastic wave propagation direction.
  • the edge region since the dielectric material layer is located on the temperature compensation dielectric layer, the speed of the acoustic wave is made slower than that in the central region.
  • the dielectric material layer is partially laminated on the lower dielectric layer portion, and the lower dielectric layer is further covered so as to cover the dielectric material layer.
  • An upper dielectric layer portion is laminated on the portion.
  • the upper surface of the upper dielectric layer portion protrudes upward by the thickness of the dielectric material layer, and a protruding portion is formed. As the thickness of the dielectric material layer increases, the amount of protrusion upward of the protrusion increases.
  • the protective film is made of a different dielectric from the upper dielectric layer portion.
  • the protruding amount of the protruding portion increases, the formed protective film tends to be thin on the side surface of the protruding portion.
  • the protrusion amount becomes larger, a hole may be formed in the protective film between the side surface of the protrusion and the portion outside the protrusion.
  • An object of the present invention is to provide an acoustic wave device in which a hole in a protective film made of another dielectric material laminated on a dielectric layer is hardly generated.
  • An acoustic wave device includes a piezoelectric substrate, and an IDT electrode provided on the piezoelectric substrate and having first and second electrode fingers that are interleaved with each other.
  • a region where the first electrode finger and the second electrode finger overlap when viewed from the elastic wave propagation direction is defined as a cross region, and the cross region includes a central region where the acoustic velocity of the elastic wave is relatively high; The sound velocity is lower than that of the central region, and low sound velocity portions provided at both ends in the direction in which the electrode fingers extend with respect to the central region.
  • the first dielectric layer above the said low sound speed material layer has a protruding portion that protrudes above the other part, the low sound speed material layer density of 7 g / cm 3 or more low Made of sonic material.
  • the said protrusion part has appeared as a protrusion part which protrudes upwards in the cross section in alignment with the extension direction of the said 1st, 2nd electrode finger of the said IDT electrode. .
  • the protruding portion appears in a cross section of the elastic wave device along the elastic wave propagation direction. In this case, it is possible to more effectively suppress the hole opening between the protruding portion and the portion located outside in the elastic wave propagation direction with respect to the protruding portion.
  • the low sound velocity material layer positioned below the projecting portion extends in the direction in which the first and second electrode fingers extend or the elastic wave propagation.
  • a cross section along at least one of the directions has a trapezoidal shape.
  • the second dielectric layer is less likely to be perforated.
  • the low sound velocity material layer is made of metal.
  • the density of the low sound velocity material layer is increased, the inclination of the side surface of the protruding portion can be further softened.
  • the low sound velocity material layer is made of a dielectric.
  • the low sound velocity material layer can be laminated directly on the first and second electrode fingers so as to extend in the elastic wave propagation direction.
  • the low acoustic velocity material layer extends so as to straddle the plurality of lower first and second electrode fingers along the elastic wave propagation direction. Has been. In this case, patterning when forming the low sound velocity material layer is easy.
  • the low sound velocity material layer is located immediately above the first electrode finger or the second electrode finger, and the first and second electrodes It does not reach between the electrode fingers.
  • the low sound velocity material layer is directly laminated on the first or second electrode finger.
  • the low acoustic velocity material layer is laminated above the first or second electrode finger via the first dielectric layer.
  • the second dielectric layer provided on the first dielectric layer it is difficult for the second dielectric layer provided on the first dielectric layer to be perforated.
  • FIG. 1 is a plan view showing an electrode structure and a low sound velocity material layer of an acoustic wave device according to a first embodiment of the present invention.
  • FIG. 2 is a front cross-sectional view for explaining the acoustic wave device according to the first embodiment of the present invention.
  • FIG. 3 is a partially enlarged sectional view of a portion along the line AA in FIG.
  • FIG. 4 is a partially enlarged sectional view of a portion along the line BB in FIG.
  • FIG. 5 is a partially enlarged sectional view of a portion along the line CC in FIG.
  • FIG. 6 is a diagram illustrating the relationship between the width of the low sound velocity part and the electromechanical coupling coefficient of the first-order mode and the third-order or higher-order mode.
  • FIG. 7 is a diagram showing the relationship between the film thickness of the low sound velocity material layer and the sound velocity ratio of the low sound velocity portion, which is the ratio of the sound velocity of the low sound velocity portion to the sound velocity of the high sound velocity portion.
  • FIG. 8 is a diagram showing the relationship between the type of the low sound velocity material and the film thickness of the low sound velocity material layer necessary for suppressing the transverse mode.
  • FIG. 9 is a plan view showing the relationship between the electrode structure and the low acoustic velocity material layer of the acoustic wave device according to the second embodiment of the present invention.
  • FIG. 10 is a partial enlarged cross-sectional view of an acoustic wave device corresponding to a portion along the line DD in FIG. 9 in the second embodiment of the present invention.
  • FIG. 11 is a partially enlarged cross-sectional view for explaining the acoustic wave device of the third embodiment.
  • FIG. 12 is a partially enlarged cross-sectional view for explaining the acoustic wave device of the third embodiment.
  • FIG. 13 is a partial enlarged cross-sectional view of an elastic wave device of a comparative example.
  • FIG. 1 is a plan view showing an electrode structure and a low sound velocity material layer of an elastic wave device according to a first embodiment of the present invention
  • FIG. 2 is a front sectional view of the elastic wave device of the present embodiment.
  • the elastic wave device 1 has a piezoelectric substrate 2.
  • An IDT electrode 3 is provided on the piezoelectric substrate 2.
  • Reflectors 4 and 5 are provided on both sides of the IDT electrode 3 in the elastic wave propagation direction.
  • a first dielectric layer 6 is provided so as to cover the IDT electrode 3.
  • a second dielectric layer 7 is provided on the first dielectric layer 6.
  • FIG. 2 shows a cross section along the elastic wave propagation direction in the center region of the IDT electrode described later.
  • the piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiNbO 3 or LiTaO 3 or a piezoelectric ceramic.
  • the IDT electrode 3 and the reflectors 4 and 5 are made of an appropriate metal or alloy.
  • the first dielectric layer 6 is provided to reduce the absolute value of the frequency temperature coefficient TCF. That is, the first dielectric layer 6 is provided as a temperature compensation dielectric film.
  • the first dielectric layer 6 is made of dielectric ceramics such as silicon oxide or silicon oxynitride.
  • first dielectric layer 6 may be provided as a layer that performs other functions.
  • the second dielectric layer 7 is provided as a moisture-resistant protective film.
  • a second dielectric layer 7 is made of an appropriate dielectric material that has better moisture resistance than the first dielectric layer 6. Examples of such a dielectric material include silicon nitride.
  • the second dielectric layer 7 is not limited to a protective film for moisture resistance, but may be an appropriate protective film for protecting the first dielectric layer 6 and the IDT electrode 3 or the like, or the frequency is adjusted. It may be a dielectric film.
  • FIG. 1 is an enlarged view showing a portion where the IDT electrode 3 is provided, and is a plan view for explaining an electrode structure and a low sound velocity material layer.
  • the IDT electrode 3 has a plurality of first electrode fingers 8 and a plurality of second electrode fingers 9.
  • the first electrode finger 8 and the second electrode finger 9 are interleaved with each other.
  • This elastic wave propagation direction E is a direction orthogonal to the direction in which the first and second electrode fingers 8 and 9 extend.
  • a region where the first electrode finger 8 and the second electrode finger 9 overlap when viewed from the elastic wave propagation direction E is an intersection region F.
  • an elastic wave is excited.
  • low sound velocity material layers 11 and 12 are provided above the first and second electrode fingers 8 and 9 at the tip portions of the first and second electrode fingers 8 and 9, respectively. ing.
  • the low acoustic velocity material layers 11 and 12 are made of a metal having a density of 7 g / cm 3 or more.
  • metals include Pt, Au, Cu, Ta, W, Ag, Ni, Mo, NiCr and the like.
  • the low sound velocity material layers 11 and 12 may be made of a low sound velocity material other than a metal having a density of 7 g / cm 3 or more. That is, even if it is a dielectric material, a semiconductor, etc., if it is a material with a density of 7 g / cm 3 or more, it can be used as a low sound velocity material.
  • the portions where the low sound velocity material layers 11 and 12 are provided are the low sound velocity portions H1 and H2.
  • the width of the low sound velocity part is a dimension along the extending direction of the first and second electrode fingers 8 and 9 of the low sound velocity material layers 11 and 12.
  • the intersecting region F includes a central region G located in the center in the extending direction of the first and second electrode fingers 8 and 9 and a direction in which the first and second electrode fingers 8 and 9 extend with respect to the central region G. And the low sound velocity portions H1 and H2 disposed at both ends of the central region G.
  • the sound velocity is lower than that in the central region G.
  • high sound speed portions I1 and I2 are provided outside the low sound speed portions H1 and H2 in the direction in which the first and second electrode fingers 8 and 9 extend.
  • the low sound velocity portions H1 and H2 are provided on both sides of the central region G, and the high sound velocity portions I1 and I2 are provided outside the low sound velocity portions H1 and H2, respectively. can do.
  • the transverse mode refers to a higher-order mode than the main mode used in the elastic wave device 1.
  • the acoustic wave device 1 uses a fundamental wave, that is, a first-order mode.
  • FIG. 1 shows the positional relationship between the IDT electrode 3 and the low sound velocity material layers 11 and 12 disposed above the IDT electrode 3.
  • the low acoustic velocity material layers 11 and 12 are separated upward via the first and second electrode fingers 8 and 9 and a part of the first dielectric layer 6.
  • Yes. 3 to 5 are partially enlarged sectional views showing a portion along the line AA, a portion along the line BB, and a portion along the line CC in FIG. 1 in the acoustic wave device 1.
  • FIG. 1 shows the positional relationship between the IDT electrode 3 and the low sound velocity material layers 11 and 12 disposed above the IDT electrode 3.
  • the low acoustic velocity material layers 11 and 12 are separated upward via the first and second electrode fingers 8 and 9 and a part of the first dielectric layer 6.
  • Yes. 3 to 5 are partially enlarged sectional views showing a portion along the line AA, a portion along the line BB, and a portion along the line CC in FIG. 1 in the acoustic wave
  • the first dielectric layer 6 and the second dielectric layer 7 are formed on the portion where the first electrode finger 8 and the second electrode finger 9 are provided. Are stacked.
  • a protruding portion 6a1 protruding upward is formed at a portion where the first electrode finger 8 and the second electrode finger 9 are provided.
  • the amount of protrusion h above the protrusion 6a1 is not so large. Therefore, the inclination of the side surface 6a11 of the protrusion 6a1 is relatively gentle. Therefore, the second dielectric layer 7 is formed with a substantially uniform thickness.
  • the gentle inclination of the side surface 6a11 means that the inclination angle of the side surface 6a11 with respect to the upper surface 6a of the first dielectric layer 6 outside the protrusion 6a1 is small.
  • the large inclination means that the inclination angle of the side surface 6a11 with respect to the upper surface 6a of the first dielectric layer 6 is large.
  • a low sound velocity material layer 11 is disposed in the first dielectric layer 6 in the direction along the elastic wave propagation direction in the low sound velocity portion.
  • the low sound velocity material layer 11 is made of metal.
  • the dielectric layer portion 6 b below the low acoustic velocity material layer 11 is formed.
  • the low acoustic velocity material layer 11 is formed.
  • an upper dielectric layer portion 6c that covers the low acoustic velocity material layer 11 is formed.
  • a second dielectric layer 7 is formed.
  • the above-described protrusion 6a1 appears above the portion where the first electrode finger 8 and the second electrode finger 9 are provided in the elastic wave propagation direction. .
  • the protruding amount of the protruding portion 6a1 is not so large. Therefore, even if the second dielectric layer 7 having a small thickness is provided, it is difficult for a portion having a very thin film thickness to be formed and a hole is not easily formed.
  • FIG. 13 is a partially enlarged cross-sectional view of the elastic wave device of the comparative example corresponding to the portion along the line CC in FIG. 1, similarly to FIG.
  • the slope of the side surface 106a11 of the protrusion 106a1 on the upper surface 106a of the first dielectric layer 106 is large. Therefore, when the second dielectric layer 107 is formed, the thickness of the second dielectric layer 107 is reduced between the side surface 106a11 and the outside of the protruding portion 106a1, and a hole 107a is generated. This is because the thickness of the low sound velocity material layer 111 is relatively large, and thus the difference in height between the upper surface 106a of the first dielectric layer 106 is large between the protruding portion 106a1 and the outer portion thereof. .
  • the inclination of the side surface 6a11 of the protrusion 6a1 is gentle.
  • the density of the low sound velocity material layer 11 is made of a low sound velocity material having a density of 7 g / cm 3 or more, and the thickness thereof is reduced. That is, since the thickness of the low acoustic velocity material layer 11 can be reduced, as shown in FIG. 5, it is difficult for the second dielectric layer 7 to be perforated. Therefore, in the acoustic wave device 1, moisture resistance can be reliably improved.
  • FIG. 6 is a diagram showing the relationship between the width ( ⁇ ) of the low sound velocity part and the electromechanical coupling coefficient of the first-order mode and the higher-order mode higher than the third-order mode in the elastic wave device 1 of the first embodiment. is there.
  • the sound speed in this case is 0.977 times the sound speed of the low sound speed section, where the sound speed in the central region is 1.
  • ⁇ is a wavelength determined by the electrode finger pitch of the IDT electrode 3.
  • the scale on the right side of FIG. 6 shows the elastic wave to be used, that is, the electromechanical coupling coefficient of the first-order mode
  • the scale on the left side shows the electromechanical coupling coefficient of the higher-order mode of the third-order mode or more, that is, the transverse mode .
  • the sound velocity ratio of the low sound velocity portion is obtained on the assumption of the following structure.
  • LiNbO 3 substrate / IDT electrode with a cut angle of 126.5 ° (NiCr: 10 nm thick, Pt: 23 nm thick, Ti: 10 nm thick, Al: 130 nm thick, Ti: 10 nm thick laminate), first dielectric layer ( SiO 2 : thickness 480 nm), second dielectric layer (SiN: thickness 20 nm).
  • the duty of the IDT electrode is 0.5.
  • the wavelength determined by the electrode finger pitch was changed under the above conditions.
  • the frequency corresponding to the sound speed in the central region is obtained from the resonance frequency of the resonance characteristics.
  • the frequency of the high sound velocity portion outside the low sound velocity portion is determined according to the material and structure.
  • the resonance frequency in the central region is 2600 MHz
  • the frequency of the high sound velocity part is 2813 MHz.
  • the sound velocity ratio with respect to the central region of the high sound velocity portion is 1.08 times.
  • the electromechanical coupling coefficients of the primary mode and the transverse mode change as shown in FIG.
  • the sound speed ratio with respect to the central area of the low sound speed portion that is, the sound speed ratio of the low sound speed portion is 0.977
  • the transverse mode can be reliably suppressed when the width of the low sound speed portion is around 0.652. Recognize.
  • FIG. 7 shows the film thickness of the low sound velocity material layer and the sound velocity ratio of the low sound velocity portion when the distance from the upper surface of the first and second electrode fingers to the lower surface of the low sound velocity material layer is 5 nm. It is a figure which shows the relationship.
  • FIG. 7 shows the results when the low acoustic velocity material layer is Pt, Au, W, Ta, Ag, Mo, Cu, Ni, Ti, or Al. As is clear from FIG. 7, it can be seen that the required film thickness differs depending on the material of the low sound velocity material layer in order to set the sound velocity ratio of the low sound velocity portion to 0.977.
  • FIG. 8 shows the relationship between the kind of low sound velocity material necessary for setting the sound velocity ratio of the low sound velocity portion to 0.977, that is, necessary for suppressing the transverse mode, and the film thickness of the low sound velocity material layer.
  • FIG. 8 it can be seen that the thickness of the low sound velocity material layer can be reduced by using Pt or Au having a high density.
  • the density of the low acoustic velocity material layer is 7 g / cm 3 or more, the thickness of the low acoustic velocity material layers 11 and 12 can be made very thin. Therefore, as shown in FIG. 5, the height of the protrusion 6a1 on the upper surface 6a of the first dielectric layer 6 can be reduced. Therefore, the inclination of the side surface 6a11 of the protrusion 6a1 can be made gentle, and the occurrence of holes in the second dielectric layer 7 can be reliably suppressed.
  • the side surfaces 11a and 11b located on the outer side in the width direction of the low sound velocity portion of the low sound velocity material layer 11 are tapered. That is, the side surfaces 11a and 11b are inclined so as to be located on the center side in the width direction of the low acoustic velocity material layer 11 as going upward. Therefore, also in the part of the first dielectric layer 6 that covers the low sound velocity material layer 11, the inclination of the side surface 6a11 of the protrusion 6a1 is gentle. Therefore, even in this case, a portion where the film thickness of the second dielectric layer 7 becomes thin is hardly generated, and the occurrence of the hole is further effectively suppressed.
  • the side surfaces 11a and 11b of the low acoustic velocity material layer 11 need not be tapered.
  • the low acoustic velocity material layer 11 has a trapezoidal shape in the cross section shown in FIG.
  • the inclination of the side surface 6a11 of the protrusion 6a1 can be made gentle as described above.
  • the cross section along the elastic wave propagation direction E of the low acoustic velocity material layer 11 may have a trapezoidal shape. In that case, in the elastic wave propagation direction E, the side surface 6a11 of the protrusion 6a1 is inclined. Can be relaxed.
  • the cross-sectional shape of the low-sonic material layer 11 is trapezoidal in both the cross-section along the direction in which the first and second electrode fingers 8 and 9 extend and the cross-section along the elastic wave propagation direction E. There may be.
  • the thickness of the low sound velocity material layers 11 and 12 can be reduced, the inclination of the side surface 6a11 of the protruding portion 6a1 can be made gentle in the direction shown in FIG. Therefore, even in the elastic wave propagation direction, it is difficult for the second dielectric layer 7 to be perforated between the protrusion 6a1 and the outer portion.
  • FIG. 9 is a plan view showing the relationship between the electrode structure and the low sound velocity material layer in the elastic wave device according to the second embodiment of the present invention.
  • the low sound velocity material layers 11 and 12 extending in the elastic wave propagation direction E are provided.
  • the low acoustic velocity material layers 21 and 22 are provided in the elastic wave device of the second embodiment.
  • the low sound velocity material layer 21 is provided on the first and second electrode fingers 8 and 9 in a portion constituting one low sound velocity portion H1, and between the first and second electrode fingers 8 and 9. It is not provided in the area.
  • the low sound velocity material layer 22 is provided on the first and second electrode fingers 8 and 9 in the other low sound velocity portion H2. In the region between the first and second electrode fingers 8 and 9, the low sound velocity material layer 22 is not provided.
  • the low sonic material layer 21 or the low sonic material layer 22 is directly laminated on the first and second electrode fingers 8 and 9.
  • the first and second electrode fingers 8 and 8 are arranged so as not to reach the region between the first and second electrode fingers 8 and 9.
  • Low-speed material layers 21 and 22 may be provided only above 9.
  • the low sound velocity material layers 21 and 22 are made of the low sound velocity material having the density of 7 g / cm 3 or more. Therefore, the inclination of the side surface 6a11 of the protrusion 6a1 can be relaxed not only in the cross width direction of the first and second electrode fingers 8 and 9, but also in the elastic wave propagation direction E. Therefore, when the second dielectric layer 7 is laminated, it is difficult for a hole to be formed in the portion between the protruding portion 6a1 and the outer region.
  • the low sound velocity material layer may be directly laminated on the first and second electrode fingers. Therefore, the low acoustic velocity material layers 11 and 12 in the elastic wave device 1 of the first embodiment may also be provided so as to be in direct contact with the upper surfaces of the first and second electrode fingers 8 and 9. However, in that case, in order to prevent a short circuit, the low sound velocity material layers 11 and 12 need to be made of an insulating dielectric material.
  • FIG. 11 and FIG. 12 are enlarged partial sectional views of an elastic wave device according to the third embodiment of the present invention.
  • FIG. 11 is a partial enlarged cross-sectional view of a portion corresponding to FIG. 4 for the first embodiment
  • FIG. 12 is a partial enlarged cross-sectional view of a portion corresponding to FIG. 5 for the first embodiment.
  • the acoustic wave device according to the third embodiment low sound velocity material layers 31 and 32 are provided.
  • the low acoustic velocity material layers 31 and 32 are not continuous in the elastic wave propagation direction, and are laminated only on the first electrode finger 8 or the second electrode finger 9. .
  • the elastic wave device of the third embodiment is the same as the elastic wave device 1 of the first embodiment.
  • the low sound velocity material layer may be directly laminated on the electrode finger.
  • the low sound velocity material layers 21 and 22 are disposed above the first and second electrode fingers 8 and 9 through a part of the first dielectric layer 6 as in the first embodiment. It may be laminated indirectly.
  • the low sound velocity material layers 11 and 12 are extended along the elastic wave propagation direction E so as to straddle the plurality of first and second electrode fingers 8 and 9. Therefore, patterning when forming the low acoustic velocity material layers 11 and 12 is easy.

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  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

Provided is an elastic wave device in which holes are unlikely to be produced in a protective film that comprises another dielectric material laminated on a dielectric layer. An IDT electrode 3 is provided on a piezoelectric substrate 2, and an intersecting region of the IDT electrode 3 has a central region in which the sound velocity of an elastic wave is relatively high, and first and second low-sound-velocity sections provided on both sides of the central region in an intersection width direction in which first and second electrode fingers 8, 9 extend, low-sound-velocity material layers 11, 12 being laminated directly or indirectly on the first and second electrode fingers 8, 9 in the first and second low-sound-velocity sections. A first dielectric layer 6, and a second dielectric layer 7 provided on the first dielectric layer 6, are provided so as to cover the IDT electrode 3 and the low-sound-velocity material layers 11, 12. The first dielectric layer 6 has a projecting section 6a1 that projects higher than the other portions above the low-sound-velocity material layers 11, 12. The low-sound-velocity material layers 11, 12 comprise a low-sound-velocity material having a density of 7 g/cm3 or greater.

Description

弾性波装置Elastic wave device
　本発明は、ピストンモードを利用した弾性波装置に関する。 The present invention relates to an elastic wave device using a piston mode.
　下記の特許文献１には、ピストンモードを利用した弾性波装置が開示されている。特許文献１の図１５では、圧電基板上に、ＩＤＴ電極、誘電体層、低音速部としてのエッジ領域を構成するための誘電体材料層及び保護膜がこの順序で積層されている。誘電体材料層は、ＩＤＴ電極の一方の電極指及び他方の電極指の先端部分の上方に設けられている。それによって、交差領域において、電極指の延びる方向中央に位置している中央領域と、中央領域の両側に配置されているエッジ領域とが設けられている。交差領域とは、一方の電位に接続される電極指と他方の電位に接続される電極指とが弾性波伝搬方向にみたときに重なり合っている領域である。エッジ領域では、誘電体材料層が温度補償用誘電体層上に位置しているため、音響波の速度が、中央領域に比べて遅くされている。 The following Patent Document 1 discloses an elastic wave device using a piston mode. In FIG. 15 of Patent Document 1, an IDT electrode, a dielectric layer, a dielectric material layer for forming an edge region as a low sound velocity portion, and a protective film are laminated in this order on a piezoelectric substrate. The dielectric material layer is provided above one electrode finger of the IDT electrode and the tip portion of the other electrode finger. Thereby, in the intersecting region, a central region located in the center of the electrode fingers in the extending direction and edge regions arranged on both sides of the central region are provided. The intersecting region is a region where an electrode finger connected to one potential and an electrode finger connected to the other potential overlap when viewed in the elastic wave propagation direction. In the edge region, since the dielectric material layer is located on the temperature compensation dielectric layer, the speed of the acoustic wave is made slower than that in the central region.
特開２０１１－１０１３５０号公報JP2011-101350A
　特許文献１に記載の弾性波装置では、下方の誘電体層部分上に、部分的に、上記誘電体材料層が積層されており、さらに誘電体材料層を覆うように、下方の誘電体層部分上に上方の誘電体層部分が積層されている。この場合、誘電体材料層が設けられている部分の上方では、誘電体材料層の厚みの分、上方の誘電体層部分の上面が上方に突出し、突出部が形成されることになる。誘電体材料層の厚みが厚くなると、突出部の上方への突出量が大きくなる。 In the elastic wave device described in Patent Document 1, the dielectric material layer is partially laminated on the lower dielectric layer portion, and the lower dielectric layer is further covered so as to cover the dielectric material layer. An upper dielectric layer portion is laminated on the portion. In this case, above the portion where the dielectric material layer is provided, the upper surface of the upper dielectric layer portion protrudes upward by the thickness of the dielectric material layer, and a protruding portion is formed. As the thickness of the dielectric material layer increases, the amount of protrusion upward of the protrusion increases.
　他方、保護膜は、上方の誘電体層部分と異なる誘電体からなる。上記突出部の突出量が大きくなると、成膜された保護膜が、突出部の側面において薄くなりがちであった。さらに、突出量がより大きくなると、突出部の側面と、突出部の外側の部分との間で、保護膜に穴開きが生じることがあった。 On the other hand, the protective film is made of a different dielectric from the upper dielectric layer portion. When the protruding amount of the protruding portion increases, the formed protective film tends to be thin on the side surface of the protruding portion. Furthermore, when the protrusion amount becomes larger, a hole may be formed in the protective film between the side surface of the protrusion and the portion outside the protrusion.
　本発明の目的は、誘電体層上に積層される他の誘電体材料からなる保護膜の穴開きが生じ難い、弾性波装置を提供することにある。 An object of the present invention is to provide an acoustic wave device in which a hole in a protective film made of another dielectric material laminated on a dielectric layer is hardly generated.
　本発明に係る弾性波装置は、圧電基板と、前記圧電基板上に設けられており、互いに間挿し合っている第１及び第２の電極指を有するＩＤＴ電極とを備え、前記ＩＤＴ電極において、前記第１の電極指と前記第２の電極指とが、弾性波伝搬方向からみたときに重なり合っている領域を交差領域とし、該交差領域が、弾性波の音速が相対的に高い中央領域と、前記中央領域よりも音速が低くされており、前記中央領域に対して電極指の延びる方向において両端部に設けられた低音速部とを有し、前記低音速部において、前記第１，第２の電極指に直接または間接に積層された低音速材料層と、前記ＩＤＴ電極及び前記低音速材料層を覆うように設けられた第１の誘電体層と、前記第１の誘電体層上に設けられている第２の誘電体層とをさらに備え、前記第１の誘電体層は、前記低音速材料層の上方において、他の部分よりも上方に突出している突出部を有し、前記低音速材料層が、密度７ｇ／ｃｍ３以上の低音速材料からなる。 An acoustic wave device according to the present invention includes a piezoelectric substrate, and an IDT electrode provided on the piezoelectric substrate and having first and second electrode fingers that are interleaved with each other. A region where the first electrode finger and the second electrode finger overlap when viewed from the elastic wave propagation direction is defined as a cross region, and the cross region includes a central region where the acoustic velocity of the elastic wave is relatively high; The sound velocity is lower than that of the central region, and low sound velocity portions provided at both ends in the direction in which the electrode fingers extend with respect to the central region. A low sound velocity material layer laminated directly or indirectly on two electrode fingers, a first dielectric layer provided so as to cover the IDT electrode and the low sound velocity material layer, and on the first dielectric layer And a second dielectric layer provided on the substrate The first dielectric layer above the said low sound speed material layer has a protruding portion that protrudes above the other part, the low sound speed material layer density of 7 g / cm 3 or more low Made of sonic material.
　本発明に係る弾性波装置のある特定の局面では、前記突出部が、前記ＩＤＴ電極の前記第１，第２の電極指の延びる方向に沿う断面において上方に突出している突出部として現れている。この場合には、突出部と、交差幅方向において突出部の外側に位置している部分との間での穴開きをより効果的に抑制することができる。 On the specific situation with the elastic wave apparatus which concerns on this invention, the said protrusion part has appeared as a protrusion part which protrudes upwards in the cross section in alignment with the extension direction of the said 1st, 2nd electrode finger of the said IDT electrode. . In this case, it is possible to more effectively suppress the hole opening between the protrusion and the portion located outside the protrusion in the cross width direction.
　本発明に係る弾性波装置の他の特定の局面では、前記突出部が、前記弾性波伝搬方向に沿う前記弾性波装置の断面において現れている。この場合には、突出部と、突出部に対して弾性波伝搬方向において外側に位置している部分との間での穴開きをより効果的に抑制することができる。 In another specific aspect of the elastic wave device according to the present invention, the protruding portion appears in a cross section of the elastic wave device along the elastic wave propagation direction. In this case, it is possible to more effectively suppress the hole opening between the protruding portion and the portion located outside in the elastic wave propagation direction with respect to the protruding portion.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記突出部の下方に位置している前記低音速材料層が、前記第１，第２の電極指の延びる方向または前記弾性波伝搬方向の少なくとも一方に沿う断面において、台形の形状を有している。この場合には、第２の誘電体層の穴開きがより一層生じ難い。 In still another specific aspect of the elastic wave device according to the present invention, the low sound velocity material layer positioned below the projecting portion extends in the direction in which the first and second electrode fingers extend or the elastic wave propagation. A cross section along at least one of the directions has a trapezoidal shape. In this case, the second dielectric layer is less likely to be perforated.
　本発明に係る弾性波装置の別の特定の局面では、前記低音速材料層が、金属からなる。この場合には、低音速材料層の密度が高くなるため、突出部の側面の傾斜をより一層やわらげることができる。 In another specific aspect of the elastic wave device according to the present invention, the low sound velocity material layer is made of metal. In this case, since the density of the low sound velocity material layer is increased, the inclination of the side surface of the protruding portion can be further softened.
　本発明に係る弾性波装置の他の特定の局面では、前記低音速材料層が、誘電体からなる。この場合には、弾性波伝搬方向に延びるように、かつ第１，第２の電極指に直接低音速材料層を積層することができる。 In another specific aspect of the elastic wave device according to the present invention, the low sound velocity material layer is made of a dielectric. In this case, the low sound velocity material layer can be laminated directly on the first and second electrode fingers so as to extend in the elastic wave propagation direction.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記低音速材料層が、弾性波伝搬方向に沿って下方の複数本の前記第１，第２の電極指を跨ぐように延ばされている。この場合には、低音速材料層の形成に際してのパターニングが容易である。 In still another specific aspect of the elastic wave device according to the present invention, the low acoustic velocity material layer extends so as to straddle the plurality of lower first and second electrode fingers along the elastic wave propagation direction. Has been. In this case, patterning when forming the low sound velocity material layer is easy.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記低音速材料層が、前記第１の電極指または前記第２の電極指の直上に位置しており、前記第１，第２の電極指間には至っていない。 In still another specific aspect of the acoustic wave device according to the present invention, the low sound velocity material layer is located immediately above the first electrode finger or the second electrode finger, and the first and second electrodes It does not reach between the electrode fingers.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記低音速材料層が、前記第１または第２の電極指に直接積層されている。 In yet another specific aspect of the acoustic wave device according to the present invention, the low sound velocity material layer is directly laminated on the first or second electrode finger.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記低音速材料層が、前記第１の誘電体層を介して前記第１または第２の電極指の上方に積層されている。 In still another specific aspect of the acoustic wave device according to the present invention, the low acoustic velocity material layer is laminated above the first or second electrode finger via the first dielectric layer.
　本発明に係る弾性波装置によれば、第１の誘電体層上に設けられている第２の誘電体層の穴開きが生じ難い。 According to the acoustic wave device of the present invention, it is difficult for the second dielectric layer provided on the first dielectric layer to be perforated.
図１は、本発明の第１の実施形態に係る弾性波装置の電極構造及び低音速材料層を示す平面図である。FIG. 1 is a plan view showing an electrode structure and a low sound velocity material layer of an acoustic wave device according to a first embodiment of the present invention. 図２は、本発明の第１の実施形態の弾性波装置を説明するための正面断面図である。FIG. 2 is a front cross-sectional view for explaining the acoustic wave device according to the first embodiment of the present invention. 図３は、図１のＡ－Ａ線に沿う部分の部分拡大断面図である。FIG. 3 is a partially enlarged sectional view of a portion along the line AA in FIG. 図４は、図１のＢ－Ｂ線に沿う部分の部分拡大断面図である。FIG. 4 is a partially enlarged sectional view of a portion along the line BB in FIG. 図５は、図１のＣ－Ｃ線に沿う部分の部分拡大断面図である。FIG. 5 is a partially enlarged sectional view of a portion along the line CC in FIG. 図６は、低音速部の幅と、１次モード、及び３次以上の高次モードの電気機械結合係数との関係を示す図である。FIG. 6 is a diagram illustrating the relationship between the width of the low sound velocity part and the electromechanical coupling coefficient of the first-order mode and the third-order or higher-order mode. 図７は、低音速材料層の膜厚と、高音速部の音速に対する低音速部の音速の割合である低音速部の音速比率との関係を示す図である。FIG. 7 is a diagram showing the relationship between the film thickness of the low sound velocity material layer and the sound velocity ratio of the low sound velocity portion, which is the ratio of the sound velocity of the low sound velocity portion to the sound velocity of the high sound velocity portion. 図８は、低音速材料の種類と、横モードを抑制するのに必要な低音速材料層の膜厚との関係を示す図である。FIG. 8 is a diagram showing the relationship between the type of the low sound velocity material and the film thickness of the low sound velocity material layer necessary for suppressing the transverse mode. 図９は、本発明の第２の実施形態に係る弾性波装置の電極構造及び低音速材料層との関係を示す平面図である。FIG. 9 is a plan view showing the relationship between the electrode structure and the low acoustic velocity material layer of the acoustic wave device according to the second embodiment of the present invention. 図１０は、本発明の第２の実施形態において、図９のＤ－Ｄ線に沿う部分に相当する弾性波装置の部分拡大断面図である。FIG. 10 is a partial enlarged cross-sectional view of an acoustic wave device corresponding to a portion along the line DD in FIG. 9 in the second embodiment of the present invention. 図１１は、第３の実施形態の弾性波装置を説明するための部分拡大断面図である。FIG. 11 is a partially enlarged cross-sectional view for explaining the acoustic wave device of the third embodiment. 図１２は、第３の実施形態の弾性波装置を説明するための部分拡大断面図である。FIG. 12 is a partially enlarged cross-sectional view for explaining the acoustic wave device of the third embodiment. 図１３は、比較例の弾性波装置の部分拡大断面図である。FIG. 13 is a partial enlarged cross-sectional view of an elastic wave device of a comparative example.
　以下、図面を参照しつつ、本発明の具体的な実施形態を説明することにより、本発明を明らかにする。 Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.
　なお、本明細書に記載の各実施形態は、例示的なものであり、異なる実施形態間において、構成の部分的な置換または組み合わせが可能であることを指摘しておく。 It should be pointed out that each embodiment described in this specification is an example, and a partial replacement or combination of configurations is possible between different embodiments.
　図１は、本発明の第１の実施形態に係る弾性波装置の電極構造及び低音速材料層を示す平面図であり、図２は本実施形態の弾性波装置の正面断面図である。 FIG. 1 is a plan view showing an electrode structure and a low sound velocity material layer of an elastic wave device according to a first embodiment of the present invention, and FIG. 2 is a front sectional view of the elastic wave device of the present embodiment.
　図２に示すように、弾性波装置１は、圧電基板２を有する。圧電基板２上に、ＩＤＴ電極３が設けられている。ＩＤＴ電極３の弾性波伝搬方向両側に反射器４，５が設けられている。ＩＤＴ電極３を覆うように第１の誘電体層６が設けられている。第１の誘電体層６上に、第２の誘電体層７が設けられている。なお、図２では、後述するＩＤＴ電極の中央領域における弾性波伝搬方向に沿う断面が示されている。 As shown in FIG. 2, the elastic wave device 1 has a piezoelectric substrate 2. An IDT electrode 3 is provided on the piezoelectric substrate 2. Reflectors 4 and 5 are provided on both sides of the IDT electrode 3 in the elastic wave propagation direction. A first dielectric layer 6 is provided so as to cover the IDT electrode 3. A second dielectric layer 7 is provided on the first dielectric layer 6. FIG. 2 shows a cross section along the elastic wave propagation direction in the center region of the IDT electrode described later.
　圧電基板２は、ＬｉＮｂＯ３やＬｉＴａＯ３などの圧電単結晶あるいは圧電セラミックスなどからなる。ＩＤＴ電極３及び反射器４，５は、適宜の金属もしくは合金からなる。 The piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiNbO 3 or LiTaO 3 or a piezoelectric ceramic. The IDT electrode 3 and the reflectors 4 and 5 are made of an appropriate metal or alloy.
　第１の誘電体層６は、周波数温度係数ＴＣＦの絶対値を小さくするために設けられている。すなわち、温度補償用の誘電体膜として、第１の誘電体層６が設けられている。第１の誘電体層６は、酸化ケイ素や酸窒化ケイ素などの誘電体セラミックスなどからなる。 The first dielectric layer 6 is provided to reduce the absolute value of the frequency temperature coefficient TCF. That is, the first dielectric layer 6 is provided as a temperature compensation dielectric film. The first dielectric layer 6 is made of dielectric ceramics such as silicon oxide or silicon oxynitride.
　なお、第１の誘電体層６は、他の機能を果たす層として設けられていてもよい。 Note that the first dielectric layer 6 may be provided as a layer that performs other functions.
　第２の誘電体層７は、耐湿保護膜として設けられている。このような第２の誘電体層７は、第１の誘電体層６よりも耐湿性に優れた適宜の誘電体材料からなる。このような誘電体材料としては、窒化ケイ素などを挙げることができる。 The second dielectric layer 7 is provided as a moisture-resistant protective film. Such a second dielectric layer 7 is made of an appropriate dielectric material that has better moisture resistance than the first dielectric layer 6. Examples of such a dielectric material include silicon nitride.
　なお、第２の誘電体層７は、耐湿のための保護膜に限らず、第１の誘電体層６及びＩＤＴ電極３などを保護する適宜の保護膜であってもよく、あるいは周波数を調整するための誘電体膜であってもよい。 The second dielectric layer 7 is not limited to a protective film for moisture resistance, but may be an appropriate protective film for protecting the first dielectric layer 6 and the IDT electrode 3 or the like, or the frequency is adjusted. It may be a dielectric film.
　図１は、上記ＩＤＴ電極３が設けられている部分を拡大して示す図であり、電極構造及び低音速材料層を説明するための平面図である。 FIG. 1 is an enlarged view showing a portion where the IDT electrode 3 is provided, and is a plan view for explaining an electrode structure and a low sound velocity material layer.
　図１に示すように、ＩＤＴ電極３は、複数本の第１の電極指８と、複数本の第２の電極指９とを有する。第１の電極指８と第２の電極指９とが、互いに間挿し合っている。第１の電極指８と第２の電極指９との間に電圧を印加することにより、弾性波が励振される。この弾性波伝搬方向Ｅは、第１，第２の電極指８，９が延びる方向と直交する方向である。 As shown in FIG. 1, the IDT electrode 3 has a plurality of first electrode fingers 8 and a plurality of second electrode fingers 9. The first electrode finger 8 and the second electrode finger 9 are interleaved with each other. By applying a voltage between the first electrode finger 8 and the second electrode finger 9, an elastic wave is excited. This elastic wave propagation direction E is a direction orthogonal to the direction in which the first and second electrode fingers 8 and 9 extend.
　弾性波伝搬方向Ｅからみたときに、第１の電極指８と第２の電極指９とが重なり合っている領域が、交差領域Ｆである。交差領域Ｆにおいて、弾性波が励振されることになる。 A region where the first electrode finger 8 and the second electrode finger 9 overlap when viewed from the elastic wave propagation direction E is an intersection region F. In the intersection region F, an elastic wave is excited.
　ところで、図１に示すように、第１，第２の電極指８，９の先端部分において、第１，第２の電極指８，９の上方に、低音速材料層１１，１２が設けられている。 By the way, as shown in FIG. 1, low sound velocity material layers 11 and 12 are provided above the first and second electrode fingers 8 and 9 at the tip portions of the first and second electrode fingers 8 and 9, respectively. ing.
　本実施形態では、低音速材料層１１，１２は、密度が７ｇ／ｃｍ３以上の金属からなる。このような金属としては、Ｐｔ、Ａｕ、Ｃｕ、Ｔａ，Ｗ，Ａｇ，Ｎｉ，Ｍｏ，ＮｉＣｒなどを挙げることができる。もっとも、低音速材料層１１，１２は、密度が７ｇ／ｃｍ３以上の金属以外の低音速材料からなるものであってもよい。すなわち、誘電体や半導体などであっても、密度が７ｇ／ｃｍ３以上の材料であれば、低音速材料として用いることができる。このような誘電体としては、例えば、Ｔａ２Ｏ５（密度＝８．７３ｇ／ｃｍ３）やＨｆＯ３（密度＝９．６８ｇ／ｃｍ３）、ＷＯ３（密度＝７．１５ｇ／ｃｍ３）、ＣｅＯ２（密度＝７．３ｇ／ｃｍ３）などを挙げることができる。 In the present embodiment, the low acoustic velocity material layers 11 and 12 are made of a metal having a density of 7 g / cm 3 or more. Examples of such metals include Pt, Au, Cu, Ta, W, Ag, Ni, Mo, NiCr and the like. However, the low sound velocity material layers 11 and 12 may be made of a low sound velocity material other than a metal having a density of 7 g / cm 3 or more. That is, even if it is a dielectric material, a semiconductor, etc., if it is a material with a density of 7 g / cm 3 or more, it can be used as a low sound velocity material. Examples of such dielectrics include Ta 2 O 5 (density = 8.73 g / cm 3 ), HfO 3 (density = 9.68 g / cm 3 ), and WO 3 (density = 7.15 g / cm 3 ). And CeO 2 (density = 7.3 g / cm 3 ).
　低音速材料層１１，１２の設けられている部分が、低音速部Ｈ１，Ｈ２である。低音速部の幅とは、低音速材料層１１，１２の第１，第２の電極指８，９の延びる方向に沿う寸法である。交差領域Ｆは、第１，第２の電極指８，９の延びる方向において中央に位置している中央領域Ｇと、中央領域Ｇに対して第１，第２電極指８，９の延びる方向において中央領域Ｇの両端部に配置された上記低音速部Ｈ１，Ｈ２とを有する。 The portions where the low sound velocity material layers 11 and 12 are provided are the low sound velocity portions H1 and H2. The width of the low sound velocity part is a dimension along the extending direction of the first and second electrode fingers 8 and 9 of the low sound velocity material layers 11 and 12. The intersecting region F includes a central region G located in the center in the extending direction of the first and second electrode fingers 8 and 9 and a direction in which the first and second electrode fingers 8 and 9 extend with respect to the central region G. And the low sound velocity portions H1 and H2 disposed at both ends of the central region G.
　低音速部Ｈ１，Ｈ２では、低音速材料層１１，１２が配置されているため、中央領域Ｇに比べて、音速が低められている。他方、低音速部Ｈ１，Ｈ２の第１，第２の電極指８，９の延びる方向外側には、高音速部Ｉ１，Ｉ２が設けられている。上記のように、中央領域Ｇの両側に低音速部Ｈ１，Ｈ２が設けられており、低音速部Ｈ１，Ｈ２の外側に高音速部Ｉ１，Ｉ２がそれぞれ設けられているため、横モードを抑制することができる。 In the low sound velocity portions H1 and H2, since the low sound velocity material layers 11 and 12 are arranged, the sound velocity is lower than that in the central region G. On the other hand, high sound speed portions I1 and I2 are provided outside the low sound speed portions H1 and H2 in the direction in which the first and second electrode fingers 8 and 9 extend. As described above, the low sound velocity portions H1 and H2 are provided on both sides of the central region G, and the high sound velocity portions I1 and I2 are provided outside the low sound velocity portions H1 and H2, respectively. can do.
　なお、横モードとは、弾性波装置１で利用する主モードよりも高次のモードをいうものとする。弾性波装置１では、基本波すなわち１次のモードを利用している。 The transverse mode refers to a higher-order mode than the main mode used in the elastic wave device 1. The acoustic wave device 1 uses a fundamental wave, that is, a first-order mode.
　図１では、ＩＤＴ電極３と、ＩＤＴ電極３の上方に配置された低音速材料層１１，１２との位置関係が示されている。実際には、弾性波装置１では、低音速材料層１１，１２は、第１，第２の電極指８，９と、第１の誘電体層６の一部を介して上方に隔てられている。図３～図５は、この弾性波装置１における図１中Ａ－Ａ線に沿う部分、Ｂ－Ｂ線に沿う部分及びＣ－Ｃ線に沿う部分を示す部分拡大断面図である。 FIG. 1 shows the positional relationship between the IDT electrode 3 and the low sound velocity material layers 11 and 12 disposed above the IDT electrode 3. Actually, in the acoustic wave device 1, the low acoustic velocity material layers 11 and 12 are separated upward via the first and second electrode fingers 8 and 9 and a part of the first dielectric layer 6. Yes. 3 to 5 are partially enlarged sectional views showing a portion along the line AA, a portion along the line BB, and a portion along the line CC in FIG. 1 in the acoustic wave device 1. FIG.
　図３に示すように、中央領域Ｇにおいては、第１の電極指８及び第２の電極指９が設けられている部分上に、第１の誘電体層６及び第２の誘電体層７が積層されている。この場合、第１の誘電体層６の上面６ａにおいては、第１の電極指８及び第２の電極指９が設けられている部分において、上方に突出している突出部６ａ１が形成されている。もっとも、突出部６ａ１の上方への突出量ｈはさほど大きくない。そのため、突出部６ａ１の側面６ａ１１の傾斜は比較的ゆるやかである。よって、第２の誘電体層７がほぼ均一な厚みで形成されている。なお、側面６ａ１１の傾斜がゆるやかとは、側面６ａ１１の突出部６ａ１外の第１の誘電体層６の上面６ａに対する傾斜角度が小さいことを意味する。また、以下において、傾斜が大きいとは、逆に、側面６ａ１１の第１の誘電体層６の上面６ａに対する傾斜角度が大きいことを意味する。 As shown in FIG. 3, in the central region G, the first dielectric layer 6 and the second dielectric layer 7 are formed on the portion where the first electrode finger 8 and the second electrode finger 9 are provided. Are stacked. In this case, on the upper surface 6a of the first dielectric layer 6, a protruding portion 6a1 protruding upward is formed at a portion where the first electrode finger 8 and the second electrode finger 9 are provided. . However, the amount of protrusion h above the protrusion 6a1 is not so large. Therefore, the inclination of the side surface 6a11 of the protrusion 6a1 is relatively gentle. Therefore, the second dielectric layer 7 is formed with a substantially uniform thickness. The gentle inclination of the side surface 6a11 means that the inclination angle of the side surface 6a11 with respect to the upper surface 6a of the first dielectric layer 6 outside the protrusion 6a1 is small. In the following description, the large inclination means that the inclination angle of the side surface 6a11 with respect to the upper surface 6a of the first dielectric layer 6 is large.
　図４に示すように、低音速部において、弾性波伝搬方向に沿う方向においては、第１の誘電体層６内に、低音速材料層１１が配置されている。この低音速材料層１１は、本実施形態では、金属からなる。 As shown in FIG. 4, a low sound velocity material layer 11 is disposed in the first dielectric layer 6 in the direction along the elastic wave propagation direction in the low sound velocity portion. In the present embodiment, the low sound velocity material layer 11 is made of metal.
　弾性波装置１の製造に際しては、低音速材料層１１の下方の誘電体層部分６ｂを成膜する。次に、低音速材料層１１を形成する。その次に、低音速材料層１１を覆う上方の誘電体層部分６ｃを成膜する。次に、第２の誘電体層７を成膜する。 In manufacturing the acoustic wave device 1, the dielectric layer portion 6 b below the low acoustic velocity material layer 11 is formed. Next, the low acoustic velocity material layer 11 is formed. Next, an upper dielectric layer portion 6c that covers the low acoustic velocity material layer 11 is formed. Next, a second dielectric layer 7 is formed.
　図４に示すように、低音速部においては、弾性波伝搬方向において、第１の電極指８及び第２の電極指９が設けられている部分の上方に前述した突出部６ａ１が現れている。ここでも、突出部６ａ１の突出量はさほど大きくない。従って、厚みの薄い第２の誘電体層７を設けたとしても、膜厚が非常に薄い部分が生じ難く、穴開きが生じ難い。 As shown in FIG. 4, in the low sound velocity portion, the above-described protrusion 6a1 appears above the portion where the first electrode finger 8 and the second electrode finger 9 are provided in the elastic wave propagation direction. . Again, the protruding amount of the protruding portion 6a1 is not so large. Therefore, even if the second dielectric layer 7 having a small thickness is provided, it is difficult for a portion having a very thin film thickness to be formed and a hole is not easily formed.
　図５に示すように、本実施形態では、電極指の延びる方向においても、第２の誘電体層７において穴開きが生じ難い。これを、図１３に示す比較例と対比して説明することとする。 As shown in FIG. 5, in the present embodiment, it is difficult for the second dielectric layer 7 to be perforated even in the direction in which the electrode fingers extend. This will be described in comparison with the comparative example shown in FIG.
　図１３は、図５と同様に、図１のＣ－Ｃ線に沿う部分に相当する比較例の弾性波装置の部分拡大断面図である。図１３に示すように、電極指１０８の延びる方向においては、第１の誘電体層１０６の上面１０６ａにおける突出部１０６ａ１の、側面１０６ａ１１の傾斜が大きくなっている。そのため、第２の誘電体層１０７を成膜した場合、側面１０６ａ１１と、突出部１０６ａ１の外側との間において、第２の誘電体層１０７の厚みが薄くなり、穴開き１０７ａが生じている。これは、低音速材料層１１１の厚みが比較的厚いため、突出部１０６ａ１と、その外側の部分との間で、第１の誘電体層１０６の上面１０６ａの高さの差が大きくなることによる。 FIG. 13 is a partially enlarged cross-sectional view of the elastic wave device of the comparative example corresponding to the portion along the line CC in FIG. 1, similarly to FIG. As shown in FIG. 13, in the extending direction of the electrode finger 108, the slope of the side surface 106a11 of the protrusion 106a1 on the upper surface 106a of the first dielectric layer 106 is large. Therefore, when the second dielectric layer 107 is formed, the thickness of the second dielectric layer 107 is reduced between the side surface 106a11 and the outside of the protruding portion 106a1, and a hole 107a is generated. This is because the thickness of the low sound velocity material layer 111 is relatively large, and thus the difference in height between the upper surface 106a of the first dielectric layer 106 is large between the protruding portion 106a1 and the outer portion thereof. .
　これに対して、本実施形態の弾性波装置では、図５に示すように、突出部６ａ１の側面６ａ１１の傾斜がゆるやかになっている。これは、低音速材料層１１の密度が７ｇ／ｃｍ３以上の低音速材料からなるため、その厚みが薄くなっていることによる。すなわち、低音速材料層１１の厚みを薄くすることができるので、図５に示すように、第２の誘電体層７の穴開きが生じ難くされている。従って、弾性波装置１では、耐湿性を確実に高めることができる。 On the other hand, in the elastic wave device of the present embodiment, as shown in FIG. 5, the inclination of the side surface 6a11 of the protrusion 6a1 is gentle. This is because the density of the low sound velocity material layer 11 is made of a low sound velocity material having a density of 7 g / cm 3 or more, and the thickness thereof is reduced. That is, since the thickness of the low acoustic velocity material layer 11 can be reduced, as shown in FIG. 5, it is difficult for the second dielectric layer 7 to be perforated. Therefore, in the acoustic wave device 1, moisture resistance can be reliably improved.
　図６～図８を参照して、より詳細に説明する。 This will be described in more detail with reference to FIGS.
　図６は、第１の実施形態の弾性波装置１において、低音速部の幅（λ）と、１次モード及び３次モード以上の高次モードの電気機械結合係数との関係を示す図である。この場合の音速は、中央領域における音速を１とすると、低音速部の音速は、その０．９７７倍である。ここで、λは、ＩＤＴ電極３の電極指ピッチで定まる波長である。また、図６の右側のスケールは、利用する弾性波すなわち１次のモードの電気機械結合係数を示し、左側のスケールは、３次モード以上の高次モードすなわち横モードの電気機械結合係数を示す。 FIG. 6 is a diagram showing the relationship between the width (λ) of the low sound velocity part and the electromechanical coupling coefficient of the first-order mode and the higher-order mode higher than the third-order mode in the elastic wave device 1 of the first embodiment. is there. The sound speed in this case is 0.977 times the sound speed of the low sound speed section, where the sound speed in the central region is 1. Here, λ is a wavelength determined by the electrode finger pitch of the IDT electrode 3. Further, the scale on the right side of FIG. 6 shows the elastic wave to be used, that is, the electromechanical coupling coefficient of the first-order mode, and the scale on the left side shows the electromechanical coupling coefficient of the higher-order mode of the third-order mode or more, that is, the transverse mode .
　図６から明らかなように、低音速部の幅が０．６５２付近で１次のモードの電気機械結合係数のみ大きく、横モードの電気機械結合係数は小さい。すなわち、低音速部の幅を０．６５２付近とすることにより横モードを確実に抑制することができる。 As is clear from FIG. 6, when the width of the low sound velocity portion is around 0.652, only the electromechanical coupling coefficient of the first mode is large and the electromechanical coupling coefficient of the transverse mode is small. That is, the transverse mode can be reliably suppressed by setting the width of the low sound velocity portion to around 0.652.
　本実施形態では、以下の構造を前提として、上記低音速部の音速比率を求めた。 In this embodiment, the sound velocity ratio of the low sound velocity portion is obtained on the assumption of the following structure.
　カット角１２６．５°のＬｉＮｂＯ３基板／ＩＤＴ電極（ＮｉＣｒ：厚み１０ｎｍ、Ｐｔ：厚み２３ｎｍ、Ｔｉ：厚み１０ｎｍ、Ａｌ：厚み１３０ｎｍ、Ｔｉ：厚み１０ｎｍの積層体）、第１の誘電体層（ＳｉＯ２：厚み４８０ｎｍ）、第２の誘電体層（ＳｉＮ：厚み２０ｎｍ）。ＩＤＴ電極のデューティは０．５。 LiNbO 3 substrate / IDT electrode with a cut angle of 126.5 ° (NiCr: 10 nm thick, Pt: 23 nm thick, Ti: 10 nm thick, Al: 130 nm thick, Ti: 10 nm thick laminate), first dielectric layer ( SiO 2 : thickness 480 nm), second dielectric layer (SiN: thickness 20 nm). The duty of the IDT electrode is 0.5.
　上記条件で、電極指ピッチで定まる波長を変化させた。中央領域の音速に対応する周波数は、共振特性の共振周波数より求められる。他方、低音速部の外側の高音速部の周波数は、上記材料及び構造に従って求められる。本実施形態の一計算例では、中央領域の共振周波数が２６００ＭＨｚであり、高音速部の周波数が２８１３ＭＨｚである。この場合、高音速部の中央領域に対する音速比率は１．０８倍である。 The wavelength determined by the electrode finger pitch was changed under the above conditions. The frequency corresponding to the sound speed in the central region is obtained from the resonance frequency of the resonance characteristics. On the other hand, the frequency of the high sound velocity portion outside the low sound velocity portion is determined according to the material and structure. In one calculation example of the present embodiment, the resonance frequency in the central region is 2600 MHz, and the frequency of the high sound velocity part is 2813 MHz. In this case, the sound velocity ratio with respect to the central region of the high sound velocity portion is 1.08 times.
　この構造において、低音速部の幅を種々変化させた場合、図６に示すように１次モード及び横モードの電気機械結合係数が変化する。そして、低音速部の中央領域に対する音速比率、すなわち低音速部の音速比率を０．９７７とした時、上記低音速部の幅が０．６５２付近で、横モードを確実に抑圧し得ることがわかる。 In this structure, when the width of the low sound velocity part is changed variously, the electromechanical coupling coefficients of the primary mode and the transverse mode change as shown in FIG. When the sound speed ratio with respect to the central area of the low sound speed portion, that is, the sound speed ratio of the low sound speed portion is 0.977, the transverse mode can be reliably suppressed when the width of the low sound speed portion is around 0.652. Recognize.
　さらに、図７は、第１，第２の電極指の上面から、低音速材料層の下面までの距離が５ｎｍである場合の、低音速材料層の膜厚と、低音速部の音速比率との関係を示す図である。図７では、低音速材料層が、Ｐｔ、Ａｕ、Ｗ、Ｔａ、Ａｇ、Ｍｏ、Ｃｕ、Ｎｉ、ＴｉまたはＡｌの場合の結果が示されている。図７から明らかなように、低音速部の音速比率を０．９７７にするには、低音速材料層の材料によって必要な膜厚が異なることがわかる。すなわち、低音速材料層を構成している低音速材料の密度が高いほど、低音速部の音速比率を０．９７７にする膜厚が薄くてよいことがわかる。これを、図８に示す。図８は、上記低音速部の音速比率を０．９７７にするために必要な、すなわち横モードを抑制するために必要な低音速材料の種類と、低音速材料層の膜厚との関係を示す図である。図８から明らかなように、密度が高いＰｔやＡｕを用いることにより、低音速材料層の厚みを薄くし得ることがわかる。 Furthermore, FIG. 7 shows the film thickness of the low sound velocity material layer and the sound velocity ratio of the low sound velocity portion when the distance from the upper surface of the first and second electrode fingers to the lower surface of the low sound velocity material layer is 5 nm. It is a figure which shows the relationship. FIG. 7 shows the results when the low acoustic velocity material layer is Pt, Au, W, Ta, Ag, Mo, Cu, Ni, Ti, or Al. As is clear from FIG. 7, it can be seen that the required film thickness differs depending on the material of the low sound velocity material layer in order to set the sound velocity ratio of the low sound velocity portion to 0.977. That is, it can be seen that the higher the density of the low sound velocity material constituting the low sound velocity material layer, the thinner the film thickness that makes the sound velocity ratio of the low sound velocity portion 0.977. This is shown in FIG. FIG. 8 shows the relationship between the kind of low sound velocity material necessary for setting the sound velocity ratio of the low sound velocity portion to 0.977, that is, necessary for suppressing the transverse mode, and the film thickness of the low sound velocity material layer. FIG. As is clear from FIG. 8, it can be seen that the thickness of the low sound velocity material layer can be reduced by using Pt or Au having a high density.
　本実施形態では、低音速材料層は、密度が７ｇ／ｃｍ３以上であるため、低音速材料層１１，１２の厚みを非常に薄くすることができる。そのため、図５に示したように、第１の誘電体層６の上面６ａにおける突出部６ａ１の高さを低くすることができる。よって、突出部６ａ１の側面６ａ１１の傾斜をゆるやかにすることができ、第２の誘電体層７における穴開きの発生を確実に抑制することができる。 In this embodiment, since the density of the low acoustic velocity material layer is 7 g / cm 3 or more, the thickness of the low acoustic velocity material layers 11 and 12 can be made very thin. Therefore, as shown in FIG. 5, the height of the protrusion 6a1 on the upper surface 6a of the first dielectric layer 6 can be reduced. Therefore, the inclination of the side surface 6a11 of the protrusion 6a1 can be made gentle, and the occurrence of holes in the second dielectric layer 7 can be reliably suppressed.
　なお、第１，第２の電極指の上面から、低音速材料層の下面までの距離が、５ｎｍでない場合も同様の結果が得られることが確認されている。 It has been confirmed that the same result can be obtained even when the distance from the upper surface of the first and second electrode fingers to the lower surface of the low sound velocity material layer is not 5 nm.
　また、図５に示すように、本実施形態では、低音速材料層１１の上記低音速部の幅方向外側に位置している側面１１ａ，１１ｂにテーパーが付されている。すなわち、側面１１ａ，１１ｂは、上方にいくにつれて、低音速材料層１１の幅方向中央側に位置するように、傾斜されている。そのため、第１の誘電体層６の上記低音速材料層１１を被覆している部分においても、突出部６ａ１の側面６ａ１１の傾斜がゆるやかになっている。従って、それによっても、第２の誘電体層７の膜厚が薄くなる部分が生じ難く、かつ上記穴開きの発生がより一層効果的に抑制されている。もっとも、本発明においては、低音速材料層１１の側面１１ａ，１１ｂには、テーパーが付与されておらずともよい。 Further, as shown in FIG. 5, in the present embodiment, the side surfaces 11a and 11b located on the outer side in the width direction of the low sound velocity portion of the low sound velocity material layer 11 are tapered. That is, the side surfaces 11a and 11b are inclined so as to be located on the center side in the width direction of the low acoustic velocity material layer 11 as going upward. Therefore, also in the part of the first dielectric layer 6 that covers the low sound velocity material layer 11, the inclination of the side surface 6a11 of the protrusion 6a1 is gentle. Therefore, even in this case, a portion where the film thickness of the second dielectric layer 7 becomes thin is hardly generated, and the occurrence of the hole is further effectively suppressed. However, in the present invention, the side surfaces 11a and 11b of the low acoustic velocity material layer 11 need not be tapered.
　上記のように、低音速材料層１１の側面１１ａ，１１ｂにテーパーが付与されているため、低音速材料層１１は、図５に示されている断面において台形の形状を有している。このような台形の断面形状を有することにより、上記のように、突出部６ａ１の側面６ａ１１の傾斜をゆるやかにすることができる。なお、低音速材料層１１の弾性波伝搬方向Ｅに沿う断面が、台形の形状を有していてもよく、その場合には、弾性波伝搬方向Ｅにおいて、突出部６ａ１の側面６ａ１１の傾斜をゆるやかにすることができる。また、低音速材料層１１の第１，第２の電極指８，９の延びる方向に沿う断面と、弾性波伝搬方向Ｅに沿う断面の双方において、低音速材料層１１の断面形状が台形であってもよい。 As described above, since the side surfaces 11a and 11b of the low acoustic velocity material layer 11 are tapered, the low acoustic velocity material layer 11 has a trapezoidal shape in the cross section shown in FIG. By having such a trapezoidal cross-sectional shape, the inclination of the side surface 6a11 of the protrusion 6a1 can be made gentle as described above. In addition, the cross section along the elastic wave propagation direction E of the low acoustic velocity material layer 11 may have a trapezoidal shape. In that case, in the elastic wave propagation direction E, the side surface 6a11 of the protrusion 6a1 is inclined. Can be relaxed. Further, the cross-sectional shape of the low-sonic material layer 11 is trapezoidal in both the cross-section along the direction in which the first and second electrode fingers 8 and 9 extend and the cross-section along the elastic wave propagation direction E. There may be.
　また、上記低音速材料層１１，１２の厚みを薄くし得るため、図４に示した方向、すなわち弾性波伝搬方向においても、上記突出部６ａ１の側面６ａ１１の傾斜をゆるやかにすることができる。従って、弾性波伝搬方向においても、突出部６ａ１と、その外側の部分との間において、第２の誘電体層７に穴開きが生じ難い。 Further, since the thickness of the low sound velocity material layers 11 and 12 can be reduced, the inclination of the side surface 6a11 of the protruding portion 6a1 can be made gentle in the direction shown in FIG. Therefore, even in the elastic wave propagation direction, it is difficult for the second dielectric layer 7 to be perforated between the protrusion 6a1 and the outer portion.
　図９は、本発明の第２の実施形態の弾性波装置における電極構造と低音速材料層との関係を示す平面図である。第１の実施形態では、弾性波伝搬方向Ｅに延びる低音速材料層１１，１２が設けられていた。これに対して、第２の実施形態の弾性波装置では、低音速材料層２１，２２が設けられている。 FIG. 9 is a plan view showing the relationship between the electrode structure and the low sound velocity material layer in the elastic wave device according to the second embodiment of the present invention. In the first embodiment, the low sound velocity material layers 11 and 12 extending in the elastic wave propagation direction E are provided. On the other hand, the low acoustic velocity material layers 21 and 22 are provided in the elastic wave device of the second embodiment.
　低音速材料層２１は、一方の低音速部Ｈ１を構成する部分において、第１，第２の電極指８，９上に設けられており、第１，第２の電極指８，９間の領域には設けられていない。また、低音速材料層２２は、他方の低音速部Ｈ２において、第１，第２の電極指８，９上に設けられている。そして、第１，第２の電極指８，９間の領域においては、低音速材料層２２は設けられていない。 The low sound velocity material layer 21 is provided on the first and second electrode fingers 8 and 9 in a portion constituting one low sound velocity portion H1, and between the first and second electrode fingers 8 and 9. It is not provided in the area. The low sound velocity material layer 22 is provided on the first and second electrode fingers 8 and 9 in the other low sound velocity portion H2. In the region between the first and second electrode fingers 8 and 9, the low sound velocity material layer 22 is not provided.
　さらに、図１０に示すように、第１，第２の電極指８，９上に、低音速材料層２１または低音速材料層２２が直接積層されている。このように、本発明においては、低音速材料層２１，２２のように、第１，第２の電極指８，９間の領域に至らないように、第１，第２の電極指８，９の上方にのみ低速材料層２１，２２を設けてもよい。また、この場合、低音速材料層２１，２２は、前述した密度が７ｇ／ｃｍ３以上の低音速材料からなる。従って、第１，第２の電極指８，９の交差幅方向だけでなく、弾性波伝搬方向Ｅにおいても、突出部６ａ１の側面６ａ１１の傾斜をゆるめることができる。よって、第２の誘電体層７を積層した場合、突出部６ａ１とその外側の領域との間の部分において、穴開きが生じ難い。 Further, as shown in FIG. 10, the low sonic material layer 21 or the low sonic material layer 22 is directly laminated on the first and second electrode fingers 8 and 9. Thus, in the present invention, unlike the low sound velocity material layers 21 and 22, the first and second electrode fingers 8 and 8 are arranged so as not to reach the region between the first and second electrode fingers 8 and 9. Low-speed material layers 21 and 22 may be provided only above 9. In this case, the low sound velocity material layers 21 and 22 are made of the low sound velocity material having the density of 7 g / cm 3 or more. Therefore, the inclination of the side surface 6a11 of the protrusion 6a1 can be relaxed not only in the cross width direction of the first and second electrode fingers 8 and 9, but also in the elastic wave propagation direction E. Therefore, when the second dielectric layer 7 is laminated, it is difficult for a hole to be formed in the portion between the protruding portion 6a1 and the outer region.
　第２の実施形態から明らかなように、低音速材料層は、第１，第２の電極指に直接積層されていてもよい。従って、第１の実施形態の弾性波装置１における低音速材料層１１，１２についても、第１，第２の電極指８，９の上面に直接接触するように設けられていてもよい。もっとも、その場合には、短絡を防止するために、低音速材料層１１，１２は、絶縁性の誘電体材料からなることが必要である。 As is clear from the second embodiment, the low sound velocity material layer may be directly laminated on the first and second electrode fingers. Therefore, the low acoustic velocity material layers 11 and 12 in the elastic wave device 1 of the first embodiment may also be provided so as to be in direct contact with the upper surfaces of the first and second electrode fingers 8 and 9. However, in that case, in order to prevent a short circuit, the low sound velocity material layers 11 and 12 need to be made of an insulating dielectric material.
　図１１及び図１２は、本発明の第３の実施形態に係る弾性波装置の各部分拡大断面図である。図１１は、第１の実施形態についての図４に相当する部分の部分拡大断面図であり、図１２は、第１の実施形態についての図５に相当する部分の部分拡大断面図である。第３の実施形態の弾性波装置では、低音速材料層３１，３２が、設けられている。この場合、図１１に示すように、低音速材料層３１，３２は、弾性波伝搬方向において連なっておらず、第１の電極指８上または第２の電極指９上にのみ積層されている。その他の構成は、第３の実施形態の弾性波装置は、第１の実施形態の弾性波装置１と同様である。このように、低音速材料層は、電極指上に直接積層されていてもよい。 FIG. 11 and FIG. 12 are enlarged partial sectional views of an elastic wave device according to the third embodiment of the present invention. FIG. 11 is a partial enlarged cross-sectional view of a portion corresponding to FIG. 4 for the first embodiment, and FIG. 12 is a partial enlarged cross-sectional view of a portion corresponding to FIG. 5 for the first embodiment. In the acoustic wave device according to the third embodiment, low sound velocity material layers 31 and 32 are provided. In this case, as shown in FIG. 11, the low acoustic velocity material layers 31 and 32 are not continuous in the elastic wave propagation direction, and are laminated only on the first electrode finger 8 or the second electrode finger 9. . Otherwise, the elastic wave device of the third embodiment is the same as the elastic wave device 1 of the first embodiment. Thus, the low sound velocity material layer may be directly laminated on the electrode finger.
　また、逆に、低音速材料層２１，２２を、第１の実施形態と同様に、第１の誘電体層６の一部を介して、第１，第２の電極指８，９の上方に間接的に積層してもよい。 On the contrary, the low sound velocity material layers 21 and 22 are disposed above the first and second electrode fingers 8 and 9 through a part of the first dielectric layer 6 as in the first embodiment. It may be laminated indirectly.
　低音速材料層１１，１２では、複数本の第１，第２の電極指８，９を跨ぐように、弾性波伝搬方向Ｅに沿って延ばされている。従って、低音速材料層１１，１２の形成に際してのパターニングが容易である。 The low sound velocity material layers 11 and 12 are extended along the elastic wave propagation direction E so as to straddle the plurality of first and second electrode fingers 8 and 9. Therefore, patterning when forming the low acoustic velocity material layers 11 and 12 is easy.
１…弾性波装置
２…圧電基板
３…ＩＤＴ電極
４，５…反射器
６，７…第１，第２の誘電体層
６ａ…上面
６ａ１…突出部
６ａ１１…側面
６ｂ…下方の誘電体層部分
６ｃ…上方の誘電体層部分
８，９…第１，第２の電極指
１１，１２…低音速材料層
１１ａ，１１ｂ…側面
２１，２２，３１，３２…低音速材料層
Ｆ…交差領域
Ｇ…中央領域
Ｈ１，Ｈ２…低音速部
Ｉ１，Ｉ２…高音速部 DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 2 ... Piezoelectric substrate 3 ... IDT electrode 4, 5 ... Reflector 6, 7 ... 1st, 2nd dielectric layer 6a ... Upper surface 6a1 ... Projection part 6a11 ... Side surface 6b ... Lower dielectric layer part 6c ... Upper dielectric layer portions 8, 9 ... first and second electrode fingers 11, 12 ... low sound velocity material layers 11a, 11b ... side surfaces 21, 22, 31, 32 ... low sound velocity material layers F ... intersection region G ... Central region H1, H2 ... Low sound speed part I1, I2 ... High sound speed part

Claims (10)

  1. 　圧電基板と、
    　前記圧電基板上に設けられており、互いに間挿し合っている第１及び第２の電極指を有するＩＤＴ電極とを備え、
    　前記ＩＤＴ電極において、前記第１の電極指と前記第２の電極指とが、弾性波伝搬方向からみたときに重なり合っている領域を交差領域とし、該交差領域が、弾性波の音速が相対的に高い中央領域と、前記中央領域よりも音速が低くされており、前記中央領域に対して電極指の延びる方向において両端部に設けられた低音速部とを有し、
    　前記低音速部において、前記第１，第２の電極指に直接または間接に積層された低音速材料層と、
    　前記ＩＤＴ電極及び前記低音速材料層を覆うように設けられた第１の誘電体層と、前記第１の誘電体層上に設けられている第２の誘電体層とをさらに備え、
    　前記第１の誘電体層は、前記低音速材料層の上方において、他の部分よりも上方に突出している突出部を有し、
    　前記低音速材料層が、密度７ｇ／ｃｍ３以上の低音速材料からなる、弾性波装置。     A piezoelectric substrate;
    An IDT electrode provided on the piezoelectric substrate and having first and second electrode fingers interleaved with each other;
    In the IDT electrode, a region where the first electrode finger and the second electrode finger overlap when viewed from the elastic wave propagation direction is defined as an intersecting region, and the intersecting region has a relative acoustic velocity of the acoustic wave. A high central region, and the sound velocity is lower than that of the central region, and low sound velocity portions provided at both ends in the direction in which the electrode fingers extend with respect to the central region,
    In the low sound velocity part, a low sound velocity material layer laminated directly or indirectly on the first and second electrode fingers,
    A first dielectric layer provided to cover the IDT electrode and the low sound velocity material layer; and a second dielectric layer provided on the first dielectric layer;
    The first dielectric layer has a protruding portion protruding above the other portion above the low sound velocity material layer,
    The acoustic wave device, wherein the low sound velocity material layer is made of a low sound velocity material having a density of 7 g / cm 3 or more.
  2. 　前記突出部が、前記ＩＤＴ電極の前記第１，第２の電極指の延びる方向に沿う断面において上方に突出している突出部として現れている、請求項１に記載の弾性波装置。 The elastic wave device according to claim 1, wherein the protruding portion appears as a protruding portion protruding upward in a cross section along the extending direction of the first and second electrode fingers of the IDT electrode.
  3. 　前記突出部が、前記弾性波伝搬方向に沿う前記弾性波装置の断面において現れている、請求項１または２に記載の弾性波装置。 The elastic wave device according to claim 1 or 2, wherein the protruding portion appears in a cross section of the elastic wave device along the elastic wave propagation direction.
  4. 　前記突出部の下方に位置している前記低音速材料層が、前記第１，第２の電極指の延びる方向または前記弾性波伝搬方向の少なくとも一方に沿う断面において、台形の形状を有している、請求項２または３に記載の弾性波装置。 The low sound velocity material layer located below the protrusion has a trapezoidal shape in a cross section along at least one of the extending direction of the first and second electrode fingers or the elastic wave propagation direction. The elastic wave device according to claim 2 or 3.
  5. 　前記低音速材料層が、金属からなる、請求項１～４のいずれか１項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 4, wherein the low sound velocity material layer is made of metal.
  6. 　前記低音速材料層が、誘電体からなる、請求項１～４のいずれか１項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 4, wherein the low sound velocity material layer is made of a dielectric.
  7. 　前記低音速材料層が、弾性波伝搬方向に沿って下方の複数本の前記第１，第２の電極指を跨ぐように延ばされている、請求項１～６のいずれか１項に記載の弾性波装置。 The low sound velocity material layer is extended so as to straddle the plurality of lower first and second electrode fingers along the elastic wave propagation direction. Elastic wave device.
  8. 　前記低音速材料層が、前記第１の電極指または前記第２の電極指の直上に位置しており、前記第１，第２の電極指間には至っていない、請求項１～６のいずれか１項に記載の弾性波装置。 The low sound velocity material layer is located immediately above the first electrode finger or the second electrode finger, and does not reach between the first and second electrode fingers. The elastic wave device according to claim 1.
  9. 　前記低音速材料層が、前記第１または第２の電極指に直接積層されている、請求項１～６のいずれか１項に記載の弾性波装置。 The acoustic wave device according to any one of claims 1 to 6, wherein the low sound velocity material layer is directly laminated on the first or second electrode finger.
  10. 　前記低音速材料層が、前記第１の誘電体層を介して前記第１または第２の電極指の上方に積層されている、請求項１～７のいずれか１項に記載の弾性波装置。 The acoustic wave device according to any one of claims 1 to 7, wherein the low sound velocity material layer is laminated above the first or second electrode finger via the first dielectric layer. .
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