JP5131104B2 - Elastic wave device - Google Patents

Description

  The present invention relates to an elastic wave device using a surface acoustic wave, a boundary acoustic wave, or the like, and more specifically, an elastic wave provided with a discharge inducing portion for preventing electrode breakdown when static electricity or the like is applied. Relates to the device.

  In an RF stage of a cellular phone, a surface acoustic wave filter device is used as a bandpass filter. Patent Document 1 discloses an example of this type of surface acoustic wave filter device.

  FIG. 6 is a schematic circuit diagram showing a surface acoustic wave filter device 1001 described in Patent Document 1. As shown in FIG.

  In the surface acoustic wave filter device 1001, an electrode structure schematically shown in FIG. 6 is formed on a piezoelectric substrate 1002. On the piezoelectric substrate 1002, a plurality of series arm resonators 1005 to 1007 are connected in series with each other in a series arm extending between the input terminal 1003 and the output terminal 1004. Each of the series arm resonators 1005 to 1007 is a 1-port surface acoustic wave resonator having an IDT electrode and first and second reflectors provided on both sides of the IDT electrode.

  A parallel arm resonator 1008 is connected between the connection point between the series arm resonators 1005 and 1006 and the ground potential, and is parallel between the connection point between the series arm resonators 1006 and 1007 and the ground potential. An arm resonator 1009 is connected. Similarly, the parallel arm resonators 1008 and 1009 are formed of 1-port type acoustic wave resonators.

  In the surface acoustic wave filter device 1001, a discharge inducing pattern 1010 is connected between the input terminal 1003 and the ground potential in order to protect against static electricity. Similarly, the discharge induction pattern 1011 is connected between the output terminal 1004 and the ground potential.

Discharge induction patterns 1010 and 1011 each have a plurality of discharge inducing portion are opposed to each other across a gap _{G 1.} Taking the discharge inducing pattern 1010 as an example, the discharge inducing pattern 1010 includes a plurality of triangular protrusions 1012 connected to the input terminal 1003 and a plurality of triangular protrusions 1013 connected to the ground potential. Have And the tip of the protrusion 1012, and the tip of the protrusion 1013 are oppositely across a gap _{G 1.} In Patent Document 1, the gap G ₁ in the discharge inducing portion is smaller than the gap G ₂ between the electrode fingers connected to different potentials of the IDT electrode of the surface acoustic wave resonator.

A plurality of discharge inducing portions including the protruding portion 1012 and the protruding portion 1013 are formed. Therefore, even when static electricity is applied a plurality of times, it is said that protection from static electricity can be achieved by a plurality of discharge inducing portions.
JP 2005-191744 A

  In the surface acoustic wave filter device 1001, protection from static electricity has been achieved by providing the discharge inducing patterns 1010 and 1011 having a plurality of discharge inducing portions.

However, the interval D2 between one discharge inducing portion composed of the protrusions 1012 and 1013 and the adjacent discharge inducing portion needs to be 10 times or more the electrode finger interval D1 in the IDT electrode. However, when the discharge inducing patterns 1010 and 1011 are formed under the optimum processing conditions for forming the IDT electrode, the desired discharge inducing pattern may not be formed. For example, when the discharge inducing patterns 1010 and 1011 are formed by the photolithography-lift-off method, the width of the photoresist becomes too large, and an overhang shape suitable for etching cannot be obtained. Therefore, it is impossible to form a discharge inducing patterns 1010 and 1011 with high precision, it is difficult to set the gap G ₁ with high accuracy.

Further, in the discharge inducing patterns 1010 and 1011, when one or a plurality of discharge inducing portions are destroyed by electrostatic discharge, the generated electrode scraps adhere to the gap G ₁ of the adjacent discharge inducing portion or the vicinity thereof, and May cause an undesired short circuit. In addition, the above-mentioned electrode scraps may adhere to the electrode structure of the adjacent surface acoustic wave resonator. If the electrode soot adheres to other discharge inducing portions, IDT electrodes, or the like, the electrical characteristics of the surface acoustic wave filter device 1001 deteriorate.

  The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to ensure protection from static electricity even when static electricity is applied multiple times, and to provide an electrode portion for protection from static electricity. An object of the present invention is to provide an acoustic wave device that can be formed easily and with high accuracy, and even if static electricity is applied, it is difficult for electrode scraps to adhere.

According to the present invention, a piezoelectric substrate, an input terminal electrode and an output terminal electrode formed on the piezoelectric substrate, a ground electrode formed on the piezoelectric substrate and connected to a ground potential, and the piezoelectric An elastic wave element having an IDT electrode formed on a substrate and connected between the input terminal electrode and the output terminal electrode, and formed on the piezoelectric substrate, the input terminal electrode and the output A discharge induction electrode for inducing discharge is connected between at least one of the terminal electrodes and the ground electrode, the discharge induction electrode being the input terminal electrode or the output terminal A first electrode body connected to the electrode, and a second electrode body electrically connected to the ground electrode, and the electrode body pattern is included in the electrode pattern of the acoustic wave element unit including the IDT electrode. And, so as to form a plurality of discharge inducing portion with a narrow gap G ₁ than the narrowest gap G ₂ of the gap between the portions connected to different potentials, said first electrode body and the second electrode body A plurality of discharge induction protrusions extending from at least one of the first and second electrode bodies toward the second and first electrode bodies, and further comprising floating electrodes provided between the adjacent discharge induction portions. Provided.

In a specific aspect of the acoustic wave device according to the present invention, a plurality of floating electrodes are provided between adjacent discharge induction portions. In this case, an electrode portion for protecting against static electricity, that is, the gap G ₁ can be formed easily and with high accuracy, and even if static electricity is applied, it is possible to provide an elastic wave device in which adhesion of electrode scraps and the like hardly occurs.

According to another specific aspect of the acoustic wave device according to the present invention, at least one of the interval between the discharge induction protrusion and the floating electrode closest to the discharge induction protrusion and the interval between adjacent floating electrodes is provided. However, when the period determined by the electrode finger pitch of the IDT electrode is P, it is in the range of 0.2P to 2P. In this case, the electrode portion to Protect from static electricity, namely and the gap G ₁ can be easily formed with high precision, adhesion of the electrode debris also hardly causes acoustic wave device as static electricity is applied Can be provided.

According to still another specific aspect of the acoustic wave device according to the present invention, the distance between the discharge induction protrusion and the floating electrode closest to the discharge induction protrusion and the distance between the adjacent floating electrodes are within the range. At least one of them is substantially the same as the interval between the electrode fingers of the IDT electrode. In this case, the electrode portion to Protect from static electricity, namely and the gap G ₁ can be easily formed with high precision, adhesion of the electrode debris also hardly causes acoustic wave device as static electricity is applied Can be provided.

  In the acoustic wave device according to the present invention, the planar shape of the discharge induction protrusion is not particularly limited, but is preferably rectangular. In this case, the discharge induction protrusion can be easily formed. Moreover, the space | interval between discharge induction | guidance | derivation parts can be expanded easily, and when static electricity is added, discharge can be produced more reliably in a discharge induction | guidance | derivation part.

  In the case of the rectangular discharge induction protrusion, the width is preferably narrower than the width of the electrode finger of the IDT electrode. As a result, the stray capacitance between the portions on both sides of the gap in the discharge induction portion can be reduced.

  Note that the discharge induction protrusion may have a triangular planar shape. In that case, since the tip is sharp, it is possible to induce the discharge between the discharge induction protrusions more reliably.

  In still another specific aspect of the acoustic wave device according to the present invention, the film thickness of the discharge induction protrusion is larger than the film thickness of the floating electrode. In this case, even if the discharge due to static electricity is induced, the strength of the electrode at the discharge inducing protrusion is increased, so that it is difficult to generate electrode scraps.

  Moreover, in yet another aspect of the acoustic wave device according to the present invention, a protective film is further provided so as to cover the discharge induction part. In this case, even if discharge due to static electricity is induced, since the discharge inducing portion is covered with the protective film, it is difficult for the electrode scraps to scatter.

In still another aspect of the elastic wave device according to the present invention, in the plurality of discharge inducing protrusions, at least one value of the gap G ₁ is different from the rest of the gap G _1. In this case, even when static electricity is applied a plurality of times, electrostatic discharge can be induced in order from the side with the smallest gap. As a result, it is possible to prevent a plurality of gaps from being destroyed at the same time by a single electrostatic discharge, and to further improve the reliability of countermeasures against static electricity.

  In the acoustic wave device according to the present invention, the floating electrode is provided between the adjacent discharge induction portions. Therefore, even if the discharge induction protrusion is destroyed by the discharge, the floating electrode becomes a wall, and the electrode scrap is adjacent to the discharge. It is difficult to adhere to the guide side. Further, since the floating electrode is provided between the adjacent discharge induction portions, the pitch between the IDT electrodes can be made closer to the pitch between the electrode fingers by narrowing the interval between the discharge induction protrusion and the floating electrode. Accordingly, when the discharge induction part is formed with a processing accuracy appropriate for forming the IDT electrode, the discharge induction part can be formed with high precision.

  Therefore, according to the present invention, even when static electricity is applied a plurality of times, not only can a plurality of discharge induction portions reliably protect against static electricity, but also the discharge induction portions can be easily and highly accurate. In addition, it is possible to provide an elastic wave device excellent in reliability, in which the electrode scrap generated by the discharge is less likely to adhere to other electrode portions.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIGS. 1A and 1B are a schematic circuit diagram and a schematic plan view showing an essential part of an elastic wave device according to an embodiment of the present invention, and FIG. 2 shows an elastic wave of the present embodiment. 1 is a schematic plan view of an apparatus.

  As shown in FIG. 2, the acoustic wave device 1 is configured by forming the illustrated electrode structure on a piezoelectric substrate 2.

The piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiTaO ₃ , LiNbO ₃ or quartz, or a piezoelectric ceramic. The piezoelectric substrate 2 may have a structure in which a piezoelectric film is formed on an insulating substrate.

  A circuit configuration of an electrode structure formed on the piezoelectric substrate 2 is shown in FIG.

  In the present embodiment, an acoustic wave filter device having an input terminal electrode 3 and first and second output terminal electrodes 4 and 5 and having a balance-unbalance conversion function is configured. 3 IDT type first and second longitudinally coupled resonator type acoustic wave filter units 12 and 13 are connected to the input terminal electrode 3 via 1-port type acoustic wave resonators 6 and 7. Further, 1-port type acoustic wave resonators 8 and 9 are connected between the first acoustic wave filter unit 12 and the first output terminal 4. Similarly, 1-port type acoustic wave resonators 10 and 11 are connected between the second acoustic wave filter unit 13 and the second output terminal 5.

  As shown in FIG. 4A, the 1-port acoustic wave resonator 6 includes an IDT electrode 14 and a pair of reflectors 15 and 16 provided on both sides of the IDT electrode. The other acoustic wave resonators 7 to 11 have the same structure. In the present embodiment, a surface acoustic wave is used as the elastic wave. Accordingly, the acoustic wave resonators 6 to 11 are surface acoustic wave resonators.

  In FIG. 2, in order to facilitate the illustration of the electrode structures of the acoustic wave resonators 6 to 11, a portion having an IDT electrode and a pair of reflectors is schematically shown by a block indicated by a dashed line. Actually, as described above, each of the acoustic wave resonators 6 to 11 includes the IDT electrode 14 and the reflectors 15 and 16 disposed on both sides of the IDT electrode.

  On the other hand, the first and second elastic wave filter units 12 and 13 are 3IDT type longitudinally coupled resonator type surface acoustic wave filters. Therefore, as schematically shown in FIG. 4B, both sides of the surface wave propagation direction in the region where the first to third IDTs 17a to 17c and the IDTs 17a to 17c arranged in the surface acoustic wave propagation direction are provided. And reflectors 18a and 18b arranged on the surface.

  In FIG. 2, the portions where the IDTs and the portions where the reflectors are provided in the first and second acoustic wave filter units 12 and 13 are divided into blocks indicated by alternate long and short dash lines. Show. In FIG. 1A, only three IDTs are schematically shown as rectangular blocks, and the reflectors on both sides are not shown.

  As is clear from FIGS. 1A and 2, in the first acoustic wave filter unit 12, one end of the central second IDT is connected to the acoustic wave resonator 7, and the other end is set to the ground potential. It is connected. Further, one end of each of the first and third IDTs is connected to the acoustic wave resonator 8, and the other ends are connected in common and connected to the ground potential. Similarly, also in the 2nd elastic wave filter part 13, one end of the center 2nd IDT is connected to the elastic wave resonator 7, and the other end is connected to the ground potential. One end of each of the first and third IDTs on both sides is connected to the acoustic wave resonator 10, and the other ends are connected in common and connected to the ground potential.

  As shown in FIG. 2, the input terminal electrode 3 and the first and second output terminal electrodes 4 and 5 have a substantially rectangular planar shape. The input terminal electrode 3 and the first and second output terminal electrodes 4 and 5 are connected to the acoustic wave resonators 6 to 11 and the longitudinally coupled resonator type acoustic wave filter section 12 by the wiring pattern 21 shown in the figure. 13 is electrically connected.

  In the acoustic wave device 1, first to third discharge induction electrodes 22 to 24 are formed in order to protect against static electricity. The first discharge induction electrode 22 has one end connected to the input terminal electrode 3 and the other end connected to the ground potential. One end of each of the second and third discharge induction electrodes 23 and 24 is connected to the first and second output terminal electrodes 4 and 5, respectively, and the other end is connected to the ground potential. More specifically, as shown in FIG. 2, ground electrodes 25 and 26 are formed on the piezoelectric substrate 2, and the discharge induction electrodes 22 to 24 are electrically connected to the ground electrode 25 or the ground electrode 26. It is connected.

  The structure of the first to third discharge induction electrodes 22 to 24 will be described as a representative of the discharge induction electrode 22.

  FIG. 1B is a schematic plan view showing the discharge induction electrode 22 in an enlarged manner. As shown in FIG. 1B, the discharge induction electrode 22 includes a first electrode body 28 and a second electrode body 29. The first electrode body 28 is connected to the input terminal electrode 3, and the second electrode body 29 is electrically connected to the ground electrode 25. The first and second electrode bodies 28 and 29 are opposed to each other, and a plurality of discharge induction protrusions 28a extending from the first electrode body 28 toward the second electrode body 29 are formed at the opposed portions. ing. Similarly, a plurality of second discharge induction protrusions 29a are formed so as to protrude from the second electrode body 29 toward the first electrode body 28 side. In the present embodiment, the planar shapes of the discharge induction protrusions 28a and 29a are all triangular.

And the tip of the discharge inducing protrusions 28a, the tip of the discharge inducing protrusions 29a are opposed to each other with a gap G _1. This gap G ₁ is smaller than the narrowest gap G ₂ of the gap between the parts to be connected is present in the electrode pattern of the acoustic wave element part are formed on a piezoelectric substrate, and a different potential ing. The gap G _2, for example, may be a gap G ₂ between the electrode fingers connected to different potentials of the IDT electrode 14 of the acoustic wave resonator shown in FIG. 4 (a), FIG. 4 (b) It may be a gap between adjacent electrode fingers in the IDT electrodes 17a to 17c of the 3IDT type longitudinally coupled resonator type acoustic wave filter shown. That is, the elastic wave element unit includes not only an elastic wave resonator but also an elastic wave filter. In the acoustic wave resonator or acoustic wave filter formed on the piezoelectric substrate, the narrowest gap among the gaps between the parts connected to different potentials is not limited to the gap between the electrode fingers of the IDT electrode. ₂ . That is, the gap G ₂ is not limited to the gap between adjacent electrode fingers.

In the present embodiment, the gap G ₁ is, because it is smaller than the gap G _2, when static electricity is applied, the gap G ₁ is relatively narrow gap, discharge occurs.

  The discharge induction electrode 22 is provided with a plurality of discharge induction portions formed by facing one discharge induction protrusion 28a and one discharge induction protrusion 29a. Therefore, even if static electricity is applied and a discharge occurs in one or several discharge induction portions and the discharge induction protrusion 28a or the discharge induction protrusion 29a is destroyed, the remaining discharge induction portions are protected against the static electricity applied next time. Can be planned. Therefore, even if static electricity is applied a plurality of times, the acoustic wave device 1 can be reliably protected from static electricity.

  Furthermore, a floating electrode 30 is provided between adjacent discharge induction portions. In this embodiment, the floating electrode 30 has an elongated rectangular shape, that is, a strip shape, and the length direction thereof is a direction connecting the discharge induction protrusions 28a and 29a. Therefore, even if the discharge induction protrusion 28a or the discharge induction protrusion 29a is destroyed by discharge and electrode scraps are generated, the floating electrode 30 becomes a wall and suppresses scattering around the electrode scraps. Therefore, it is possible to suppress electrode scraps from adhering to the adjacent discharge induction portion.

  Since the floating electrode 30 is provided in order to suppress scattering to the periphery of the electrode scrap, the above-mentioned floating electrode 30 is more than the case where the floating electrode 30 is not provided regardless of the size of the floating electrode 30. Scattering of electrode scraps can be suppressed. Therefore, the dimensions of the floating electrode 30 are not particularly limited.

  However, preferably, the acoustic wave filter has a plurality of at least one of the distance A between the nearest floating electrode 30 and the discharge induction protrusions 28a and 29a and the distance B between the adjacent floating electrodes 30 and 30. It is desirable that the distance between the electrode fingers of the part and the acoustic wave resonator is substantially the same. In that case, when the IDT electrode or the like is formed by photolithography with a processing accuracy suitable for forming the IDT electrode, the discharge induction electrode 22 can be formed with high accuracy.

  As described above, it is desirable that at least one of the interval A and the interval B is substantially equal to the interval between the electrode fingers of the IDT electrode. If so, the discharge induction electrode 22 can be formed with high accuracy.

In the above-described embodiment, a plurality of discharge induction portions formed by one discharge induction protrusion 28a and one discharge induction protrusion 29a facing each other are provided. in part, the gap G ₁ is been all equal. However, the gap G ₁ in at least one of the discharge inducing portion as shown in FIG. 1 (b) by broken lines meal Z1, Z2, may be different from the gap G ₁ of the remaining discharge inducing portion. In that case, the discharge time of static electricity is applied, can be induced from a narrow gap G ₁ in sequence. Thereby, it is possible to prevent the two gaps from being destroyed simultaneously by a single electrostatic discharge.

  The electrode material for forming the IDT electrode, the wiring pattern, and the discharge inducing portion is not particularly limited, and various metals such as Ag, Cu, Al, Pt, Au, or alloys mainly composed of these metals can be used. . Further, the IDT electrode, the wiring pattern, the discharge induction portion, and the like may be formed of a laminated metal film in which a plurality of metal films are laminated.

  Preferably, the film thickness of the discharge induction protrusions 28a and 29a is larger than the film thickness of the floating electrode 30, thereby suppressing generation of electrode scraps when static electricity is applied.

  In the present embodiment, the electrode structure shown in FIG. 2 is formed on the piezoelectric substrate 2, and a protective film 20 is laminated so as to cover these electrode structures as shown in FIG. That is, the protective film 20 is formed so as to cover the discharge induction electrodes 22 to 24. Since the protective film 20 is formed, even if static electricity is applied and electrode scraps are generated, scattering of the electrode scraps around the electrode scraps can be prevented.

The material forming the protective film 20 is not particularly limited, and examples thereof include an appropriate insulating material such as a synthetic resin and an inorganic insulating material. Examples of the synthetic resin include polyimide, silicone resin, and epoxy resin. Examples of the inorganic insulating material include SiO ₂ and SiN.

  In the present embodiment, the discharge induction protrusions 28a and 29a have a triangular planar shape, and thus have sharp tips. For this reason, when static electricity is applied, the static electricity tends to concentrate on the tip of the discharge induction protrusion, so that the static electricity can be reliably discharged between the discharge induction protrusions 28a and 29a.

  However, in the present invention, the planar shape of the discharge induction protrusion is not limited to a triangle, and may be a rectangular shape as in the modification shown in FIG. In the modification shown in FIG. 5, a modification of the first discharge induction electrode 22 is shown. Here, in the portion where the first electrode main body 28 and the second electrode main body 29 face each other, a rectangular shape is formed. Strip-shaped first and second discharge induction protrusions 28b and 29b are formed. Since the planar shape of the discharge induction protrusions 28b and 29b is rectangular, the discharge induction protrusions 28b and 29b can be easily formed with high accuracy by a photolithography method or the like. Moreover, since the space | interval between adjacent discharge induction | guidance | derivation parts can be expanded, the stray capacitance between adjacent discharge induction | guidance | derivation parts can be made small.

  Preferably, the width of the strip-shaped discharge induction protrusions 28b and 29b is narrower than the width of the electrode finger of the IDT electrode, thereby reducing the stray capacitance between the adjacent discharge induction protrusions 28b and 29b. it can.

  In the present embodiment, a plurality of first discharge induction protrusions 28a are provided on the first electrode body 28 side, and a plurality of discharge induction protrusions 29a are provided on the second electrode body 29 side. However, only one of the discharge induction protrusions may be provided. For example, the discharge induction protrusion 28a may be provided only on the first electrode body 28 side, and the discharge induction protrusion 29a may be provided only on the second electrode body 29 side. However, preferably, as in the present embodiment, it is desirable that both the first and second electrode bodies 28, 29 have discharge induction protrusions 28a, 29a extending toward the other party. Thereby, it is possible to more reliably induce a discharge when static electricity is applied between the first and second discharge induction protrusions 28a and 29a.

  In the above-described embodiment, the surface acoustic wave device using the surface acoustic wave has been described. However, the present invention can also be applied to a boundary acoustic wave device using the boundary acoustic wave.

  Further, the electrode structure formed on the piezoelectric substrate is not limited to the structure shown in FIGS. 1A and 2, and the present invention can be applied to various filter devices and resonance devices.

(A) And (b) is a schematic diagram for demonstrating the circuit diagram which shows the circuit structure of the elastic wave apparatus which concerns on one Embodiment of this invention, and the 1st discharge induction electrode comprised by this embodiment. It is an enlarged plan view. 1 is a schematic plan view of an acoustic wave device according to an embodiment of the present invention. It is a partial notch front sectional drawing which shows the principal part of the elastic wave apparatus which concerns on one Embodiment of this invention. (A) And (b) is a top view which shows typically the electrode structure of the 1 port type | mold elastic wave resonator and elastic wave filter part which are comprised on the piezoelectric substrate by one Embodiment of this invention, respectively. It is a typical top view for explaining the modification of a discharge induction electrode. It is a typical top view which shows the conventional surface acoustic wave filter apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 2 ... Piezoelectric substrate 3 ... Input terminal electrode 4, 5 ... Output terminal electrode 6-11 ... Elastic wave resonator 12, 13 ... Elastic wave filter part 14 ... IDT electrode 15, 16 ... Reflector 17a-17c ... IDT
18a, 18b ... reflector 20 ... protective film 21 ... wiring pattern 22-24 ... discharge induction electrode 25, 26 ... ground electrode 28, 29 ... electrode body 28a, 28b, 29a, 29b ... discharge induction protrusion 30 ... electrode

Claims (10)

A piezoelectric substrate;
An input terminal electrode and an output terminal electrode formed on the piezoelectric substrate;
A ground electrode formed on the piezoelectric substrate and connected to a ground potential;
An elastic wave element having an IDT electrode formed on the piezoelectric substrate and connected between the input terminal electrode and the output terminal electrode;
A discharge inducing electrode formed on the piezoelectric substrate, connected between at least one of the input terminal electrode and the output terminal electrode, and the ground electrode; And the discharge induction electrode includes a first electrode body connected to the input terminal electrode or the output terminal electrode, and a second electrode body electrically connected to the ground electrode, and the IDT to the present in acoustic wave device portion of the electrode pattern in including an electrode, to form a plurality of discharge inducing portion with a narrow gap G ₁ than the narrowest gap G ₂ of the gap between the portions connected to different potentials A plurality of discharge induction protrusions extending from at least one of the first electrode body and the second electrode body toward the second and first electrode bodies,
An elastic wave device further comprising a floating electrode provided between the adjacent discharge induction portions.   The acoustic wave device according to claim 1, wherein a plurality of floating electrodes are provided between adjacent discharge induction portions.   When at least one of the interval between the discharge induction protrusion and the floating electrode closest to the discharge induction protrusion and the interval between adjacent floating electrodes is P, the period determined by the electrode finger pitch of the IDT electrode is P The elastic wave device according to claim 1 or 2, which is in a range of 0.2P to 2P.   At least one of the distance between the discharge induction protrusion and the floating electrode closest to the discharge induction protrusion and the distance between the adjacent floating electrodes is substantially the same as the distance between the electrode fingers of the IDT electrode. The elastic wave device according to claim 1 or 2.   The elastic wave device according to claim 1, wherein the discharge induction protrusion has a rectangular planar shape.   The elastic wave device according to claim 5, wherein a width of the discharge induction protrusion is smaller than a width of an electrode finger of the IDT electrode.   The elastic wave device according to any one of claims 1 to 4, wherein the discharge induction protrusion has a triangular planar shape.   The elastic wave device according to claim 1, wherein a thickness of the discharge induction protrusion is greater than a thickness of the floating electrode.   The elastic wave device according to any one of claims 1 to 8, further comprising a protective film provided so as to cover the discharge induction part. Wherein the plurality of discharge inducing protrusions, at least one value of the gap G ₁ is different from the rest of the gap G _1, the elastic wave device according to any one of claims 1-9.

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