Surface acoustic wave filter for suppressing spurious components caused by lateral mode

Abstract

Disclosed is a surface acoustic wave filter for suppressing a spurious component caused by a lateral mode, which suppresses a spurious component caused by an unnecessary lateral mode in a frequency band higher than an anti-resonant frequency or resonant frequency by having a higher sound velocity at a dummy electrode than at an interdigital transducer (IDT) electrode. The device comprises a substrate, and a supporting substrate, an energy limiting layer and a piezoelectric layer are stacked on the substrate in sequence. The first bus bar and the second bus bar extend in a first direction on the substrate and are separated from each other in a second direction perpendicular to the first direction; a plurality of first and second IDT electrodes alternately extending from the first and second bus bars in the second direction and spaced apart from each other in the first direction; a second dummy electrode extending from the second bus bar to face an end portion of each of the plurality of first IDT electrodes extending from the first bus bar; a first dummy electrode extends from the first bus bar to face an end of each of the plurality of second IDT electrodes extending from the second bus bar, a sound velocity at the dummy electrode being higher than a sound velocity at the plurality of IDT electrodes.

Description

Technical Field

[0001] The present disclosure relates to a surface acoustic wave filter for suppressing stray components caused by transverse modes, and more particularly, to a surface acoustic wave filter capable of suppressing stray components caused by unnecessary transverse modes in a frequency band higher than an antiresonance frequency or a resonance frequency by having a higher sound velocity at a dummy electrode than a sound velocity at an interdigital transducer (IDT) electrode. Background Art

[0002] Surface acoustic waves (SAW) refer to waves that propagate along the surface of an elastic solid. Surface acoustic waves propagate in the form of energy concentrated near the surface, corresponding to mechanical waves. A surface acoustic wave device is an electromechanical device that utilizes the interaction between surface acoustic waves and semiconductor conduction electrons and uses surface acoustic waves transmitted to the surface of a piezoelectric crystal. Surface acoustic wave devices can have a very wide range of applications in industrial applications including sensors, oscillators, filters, etc., and can be miniaturized and lightweight, and can also have various advantages such as robustness, stability, sensitivity, low cost, and real-time performance.

[0003] However, since unnecessary transverse modes in the surface acoustic wave filter may generate spurious components and increase insertion loss, performance may deteriorate. In order to reduce the transverse mode, a method of reducing the propagation speed of the surface acoustic wave by providing an edge portion with a low acoustic speed at an interdigital transducer (IDT) electrode has been proposed.

[0004] An example of such a surface acoustic wave filter is disclosed in Patent Document 1 (WO 2021 / 241117, PCT / JP

[0005] 2021 / 016978). The surface acoustic wave filter suppresses the stray components caused by the transverse mode as described below.

[0006] Figure 1 is a plan view of a surface acoustic wave filter 100 disclosed in Patent Document 1.

[0007] refer to Figure 1 The surface acoustic wave filter 100 includes: a substrate 110, on which a supporting substrate, an energy confinement layer and a piezoelectric layer are stacked in sequence; and a first busbar 120 and a second busbar 125, which extend along a first direction on the substrate 110 and are spaced apart from each other in a second direction perpendicular to the first direction.

[0008] Then, a plurality of first IDT electrodes 130 and a plurality of second IDT electrodes 135 are alternately extended from the first bus bar 120 and the second bus bar 125 in the second direction and are spaced apart from each other in the first direction. In addition, a second dummy electrode 155 and a first dummy electrode 150 are also provided, wherein the second dummy electrode 155 extends from the second bus bar 125 to face the end of each first IDT electrode 130 extending from the first bus bar 120, and the first dummy electrode 150 extends from the first bus bar 120 to face the end of the second IDT electrode 135 extending from the second bus bar 125.

[0009] In particular, in the region C where the first IDT electrode 130 and the second IDT electrode 135 coexist in the second direction and are spaced apart from each other in the first direction, edge portions with a lower sound velocity than the center portion are arranged at both ends of the center portion.

[0010] refer to Figure 1 Of the regions shown on the left side, the region corresponding to C2 or C3 represents an edge portion, the region corresponding to C1 represents a center portion, and the sound speed of the region corresponding to C2 or C3 is configured to be lower than the sound speed of the region corresponding to C1.

[0011] like Figure 1 In the shapes of the first IDT electrode 130 and the second IDT electrode 135 shown, the electrode widths of the edge portions C2 and C3 are configured to be larger than the electrode width of the center portion C1 to form a region with low acoustic velocity.

[0012] Figure 1 The graph shown on the right indicates the sound velocity of each part. The sound velocity of the edge parts C2 and C3 is V2, and the sound velocity of the center part C1 is V3. In this case, V3>V2.

[0013] That is, the first IDT electrode 130 and the second IDT electrode 135 include the region C1 (central portion) and regions C2 and C3 (edge ​​portions) having a sound velocity lower than that of the region C1 (central portion).

[0014] Meanwhile, the applicant of the present disclosure has also developed a surface acoustic wave filter that uses another method to implement the edge portion as a low sound velocity area. Figure 2 and Figure 3 Described in .

[0015] Figure 2 FIG. 1 is a diagram showing a surface acoustic wave filter in which a mass addition film 160 is arranged on an electrode. Figure 3 yes Figure 2 Cross-sectional view of the AA' section of the surface acoustic wave filter.

[0016] refer to Figure 2 and Figure 3The mass additional film 160 is disposed on the upper surface of the C2 and C3 regions of the IDT electrode to realize the C2 and C3 regions as low acoustic velocity regions.

[0017] At this time, the density of the mass added film 160 is 5 g / cm 3 or less, including at least one material selected from silicon dioxide (SiO2), tantalum pentoxide (Ta2O5) and aluminum oxide (Al2O3).

[0018] Thus, it can be understood that the mass added film 160 is arranged at a portion corresponding to the low sound velocity region to reduce the sound velocity of the low sound velocity region from V3 to V2, thereby suppressing the spurious component caused by the transverse mode as disclosed in the cited patent document.

[0019] However, all of the techniques described above are limited to realizing the edge portion as a low sound velocity region.

[0020] It can be verified that the realization of the low sound velocity region is effective in suppressing the spurious components caused by the transverse mode. However, since spurious components are still generated in the frequency band higher than the antiresonance frequency, improvement is required.

[0021] [Prior art documents]

[0022] [Patent Document]

[0023] (Patent Document 1) International Patent Publication No. WO 2021 / 241117, PCT / JP 2021 / 016978 Summary of the invention

[0024] Therefore, the present disclosure has been made to solve the above-mentioned problems, and one object of the present disclosure is to provide a surface acoustic wave filter configured to suppress spurious components caused by a transverse mode in a frequency band higher than an antiresonance frequency or a resonance frequency.

[0025] The technical problems of the present disclosure are not limited to the above-mentioned technical problems, and other unmentioned technical problems will be clearly understood by those skilled in the art from the following description.

[0026] In order to achieve the above-mentioned purpose, according to one aspect of the present disclosure, there is provided a surface acoustic wave filter, which is configured to suppress stray components caused by a lateral mode, and includes: a substrate, on which a supporting substrate, an energy confinement layer and a piezoelectric layer are stacked in sequence; a first busbar and a second busbar, which extend along a first direction on the substrate and are spaced apart from each other in a second direction perpendicular to the first direction; a plurality of first IDT electrodes and a plurality of second IDT electrodes, which extend alternately from the first busbar and the second busbar along the second direction and are spaced apart from each other in the first direction; a second dummy electrode, which extends from the second busbar to face an end of each of the plurality of first IDT electrodes extending from the first busbar; and a first dummy electrode, which extends from the first busbar to face an end of each of the plurality of second IDT electrodes extending from the second busbar, wherein the acoustic velocity at the first dummy electrode and the second dummy electrode is higher than the acoustic velocity at the plurality of first IDT electrodes and the second IDT electrodes.

[0027] In order to achieve the above-mentioned purpose, according to another aspect of the present disclosure, there is provided a surface acoustic wave filter, which is configured to suppress stray components caused by a lateral mode, and includes: a substrate on which a supporting substrate, an energy confinement layer, and a piezoelectric layer are stacked in sequence; a first bus bar and a second bus bar, which extend along a first direction on the substrate and are spaced apart from each other in a second direction perpendicular to the first direction; a plurality of first IDT electrodes and a plurality of second IDT electrodes, which extend alternately from the first bus bar and the second bus bar along the second direction and are spaced apart from each other in the first direction; a second dummy electrode, which extends from the second bus bar to face an end of each of the plurality of first IDT electrodes extending from the first bus bar; and a first dummy electrode, which extends from the first bus bar to face an end of each of the plurality of second IDT electrodes extending from the second bus bar, wherein the stray components are suppressed in a frequency band higher than an antiresonance frequency.

[0028] In order to achieve the above-mentioned purpose, according to another aspect of the present disclosure, there is provided a surface acoustic wave filter, which is configured to suppress stray components caused by a lateral mode, comprising: a substrate on which a supporting substrate, an energy confinement layer and a piezoelectric layer are stacked in sequence; a first bus bar and a second bus bar, which extend along a first direction on the substrate and are spaced apart from each other in a second direction perpendicular to the first direction; a plurality of first IDT electrodes and a plurality of second IDT electrodes, which extend alternately from the first bus bar and the second bus bar along the second direction and are spaced apart from each other in the first direction; a second dummy electrode, which extends from the second bus bar to face an end of each of the plurality of first IDT electrodes extending from the first bus bar; and a first dummy electrode, which extends from the first bus bar to face an end of each of the plurality of second IDT electrodes extending from the second bus bar, wherein the stray components are suppressed in a frequency band higher than the resonant frequency.

[0029] In some embodiments of the present disclosure, a width of each of the first and second dummy electrodes may be smaller than a width of each of the plurality of first and second IDT electrodes.

[0030] In some embodiments of the present disclosure, the width of each of the first dummy electrode and the second dummy electrode may be configured within a range of 20% to 80% of the width of each of the plurality of first and second IDT electrodes.

[0031] In some embodiments of the present disclosure, the width of each of the first dummy electrode and the second dummy electrode may be configured to be within a range of 50% to 80% of the width of each of the plurality of first and second IDT electrodes.

[0032] In some embodiments of the present disclosure, the density of each of the first dummy electrodes and the second dummy electrodes may be higher than the density of the plurality of first IDT electrodes and the second IDT electrodes.

[0033] In some embodiments of the present disclosure, edge portions with a lower sound velocity than the central portion may be disposed on both sides of a region where a plurality of first IDT electrodes and a plurality of second IDT electrodes exist simultaneously in the second direction and are spaced apart from each other in the first direction.

[0034] In some embodiments of the present disclosure, a width of the edge portion may be greater than a width of each of the plurality of first and second IDT electrodes.

[0035] In some embodiments of the present disclosure, the density of the edge portion may be lower than the density of each of the plurality of first and second IDT electrodes.

[0036] In some embodiments of the present disclosure, the edge portion may be formed by adding a mass adding film to the plurality of first IDT electrodes and the second IDT electrodes.

[0037] In some embodiments of the present disclosure, the density of the mass-added film may be equal to or less than 5 g / cm 3 .

[0038] In some embodiments of the present disclosure, the mass-added film may include at least one selected from silicon dioxide (SiO 2 ), tantalum pentoxide (Ta 2 O 5 ), and aluminum oxide (Al 2 O 3 ).

[0039] As described above, according to the surface acoustic wave filter for suppressing stray components caused by the transverse mode of the present disclosure, it is possible to configure such that the acoustic velocity at the dummy electrode is higher than the acoustic velocity at the IDT electrode. Therefore, the stray components caused by the unnecessary transverse mode can be suppressed in the frequency band higher than the antiresonance frequency or the resonant frequency, thereby improving the characteristics of the high-frequency front-end circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a plan view of a surface acoustic wave filter in the related art.

[0041] Figure 2 FIG. 1 is a diagram showing a surface acoustic wave filter in which a mass addition film is arranged on an electrode.

[0042] Figure 3 yes Figure 2 Cross-sectional view of the AA' section of the surface acoustic wave filter.

[0043] Figure 4 is a plan view of a surface acoustic wave filter according to an embodiment of the present disclosure.

[0044] Figures 5A to 5G is a diagram showing the effect of suppressing spurious components in a surface acoustic wave filter according to an embodiment of the present disclosure.

[0045] Description of symbols

[0046] 100: Surface acoustic wave filter

[0047] 110: Substrate

[0048] 120: First busbar

[0049] 125: Second busbar

[0050] 130: First IDT electrode

[0051] 135: Second IDT electrode

[0052] 150: First dummy electrode

[0053] 155: Second dummy electrode

[0054] 160: Quality additional film DETAILED DESCRIPTION

[0055] By referring to the following detailed description of the embodiments and the accompanying drawings, the advantages and features of the present disclosure and the methods for achieving these advantages and features can be more easily understood. However, the present disclosure is not limited to the embodiments described herein and can be implemented in many different forms. The embodiments are provided to make the present disclosure thorough and complete and to fully convey the concepts of the present disclosure to those skilled in the art, and the scope of the present disclosure should be defined by the attached claims. The same reference numerals represent the same elements throughout the specification.

[0056] "And / or" includes each and every item mentioned and all combinations of one or more of the mentioned items.

[0057] The terms used herein are intended to describe embodiments rather than to limit the present disclosure. In this specification, singular forms also include plural forms unless otherwise specified. It should be further understood that the terms "comprises," "comprising," "includes," and / or "comprising" used herein mean that the components, steps, operations, and / or elements mentioned do not exclude the presence or addition of one or more other components, steps, operations, and / or elements.

[0058] It will be understood that when an element is referred to as being “connected to” or “coupled to” another element, it may be “directly connected or coupled to” the other element or “electrically connected to” the other element through an intervening element.

[0059] It should be understood that throughout the specification, when a layer (film), region, pattern or structure is referred to as being disposed "on / over" or "under / under" a substrate, another layer (film), region, pad or pattern, it may be disposed on the substrate, another layer (film), region, pad or pattern directly or indirectly with other elements in between. The reference to "on / over" or "under / under" is described based on the drawings.

[0060] In addition, expressions such as “first, second”, etc. are only used to distinguish a plurality of components, and do not limit the order or other characteristics between the components.

[0061] Furthermore, the flowcharts shown in the drawings are merely exemplary sequences for achieving the most desirable results of the present disclosure, and other steps may be added or some steps may be omitted.

[0062] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used as the meanings commonly understood by those skilled in the art. In addition, unless clearly and specifically defined, terms defined in commonly used dictionaries will not be idealized or over-interpreted.

[0063] Figure 4 is a plan view of a surface acoustic wave filter 100 according to an embodiment of the present disclosure.

[0064] refer to Figure 4 The surface acoustic wave filter 100 includes: a substrate 110 on which a supporting substrate, an energy confinement layer and a piezoelectric layer are stacked in sequence; and a first bus bar 120 and a second bus bar 125, which extend along a first direction on the substrate 110 and are spaced apart from each other in a second direction perpendicular to the first direction.

[0065] Then, a plurality of first IDT electrodes 130 and a plurality of second IDT electrodes 135 are alternately extended from the first bus bar 120 and the second bus bar 125 in the second direction and are spaced apart from each other in the first direction. In addition, a second dummy electrode 155 and a first dummy electrode 150 are also configured, wherein the second dummy electrode 155 extends from the second bus bar 125 to face the end of each first IDT electrode 130 extending from the first bus bar 120, and the first dummy electrode 150 extends from the first bus bar 120 to face the end of each second IDT electrode 135 extending from the second bus bar 125.

[0066] In the region C where the first IDT electrode 130 and the second IDT electrode 135 exist simultaneously in the second direction and are spaced apart from each other in the first direction, edge portions having a lower sound velocity than the center portion are arranged at both ends of the center portion.

[0067] The mass addition film 160 is disposed on the upper surfaces of the first IDT electrode 130 and the second IDT electrode 135 corresponding to the C2 and C3 regions to form a low acoustic velocity region.

[0068] At this time, the density of the mass added film 160 is 5 g / cm 3 or less, including at least one material selected from silicon dioxide (SiO2), tantalum pentoxide (Ta2O5) and aluminum oxide (Al2O3).

[0069] The mass added film 160 is added to the edge portion so that the acoustic velocity of the edge portion is lower than the acoustic velocity of the central portion of the first IDT electrode 130 and the second IDT electrode 135 .

[0070] Figure 4 The graph on the right shows the sound speed of each part. The sound speed of the edge parts, that is, areas C2 and C3, is V2, and the sound speed of the center part, that is, area C1, is V3. In this case, V3>V2.

[0071] That is, the first IDT electrode 130 and the second IDT electrode 135 include a region C1 (central portion), and regions C2 and C3 (edge ​​portions) having a lower acoustic velocity than the region C1 (central portion).

[0072] In particular, the surface acoustic wave filter of the present disclosure has a characteristic that the acoustic velocity at the first and second dummy electrodes 150 and 155 is higher than the acoustic velocity at the center portion C1 of the first and second IDT electrodes 130 and 135 .

[0073] The acoustic velocity at the first dummy electrode 150 and the second dummy electrode 155 is V32, and the acoustic velocity at the central portion C1 of the first IDT electrode 130 and the second IDT electrode 135 is V3. In this case, V32>V3.

[0074] The first dummy electrode 150 and the second dummy electrode 155 in the surface acoustic wave filter of the present disclosure may be configured to have a width smaller than the width of the central portion C1 of the first IDT electrode 130 and the second IDT electrode 135 so that the acoustic velocity at the first dummy electrode 150 and the second dummy electrode 155 is higher than the acoustic velocity at the central portion C1 of the first IDT electrode 130 and the second IDT electrode 135.

[0075] The density of the first and second dummy electrodes 150 and 155 may be configured to be lower than that of the first and second IDT electrodes 130 and 135 so that the acoustic velocity at the first and second dummy electrodes 150 and 155 is lower than the acoustic velocity at the center portion C1 of the first and second IDT electrodes 130 and 135 .

[0076] In the surface acoustic wave filter of the related art, the width of the dummy electrode extending from the bus bar in the direction perpendicular to the propagation of the acoustic wave is the same as the width of the central portion of the IDT electrode.

[0077] Therefore, since the acoustic velocity at the dummy electrode is the same as the acoustic velocity at the central portion of the IDT electrode, a phenomenon occurs in which a spurious component increases in a frequency band higher than the resonance frequency due to the resonance point or the like at the central portion.

[0078] It can be verified that when the acoustic velocity at the dummy electrode is higher than the acoustic velocity at the central portion of the IDT electrode, the spurious components are further suppressed in a frequency band higher than the resonance frequency.

[0079] Figures 5A to 5G is a diagram showing the effect of suppressing spurious components in a surface acoustic wave filter according to an embodiment of the present disclosure.

[0080] Figures 5A to 5G The measurement results of an experiment performed by manufacturing an IDT electrode and a dummy electrode, fixing the width of the IDT electrode at 0.65μ, and changing the width of the dummy electrode from 0.65μ, 0.55μ, 0.50μ, 0.45μ, 0.40μ, 0.35μ, 0.25μ to 0.2μ are shown.

[0081] The red curve represents the measurement results of manufacturing a dummy electrode with a width of 0.65μ, which is the same as the width of the IDT electrode, and the blue curve represents the measurement results of changing the width of the dummy electrode from 0.55μm to 0.2μm.

[0082] exist Figures 5A to 5G In the figure, when the horizontal axis represents frequency, Fr represents the resonant frequency and Fa represents the anti-resonant frequency. The vertical axis represents the output size for each frequency input. The area marked with a dotted circle is the part where the effect of suppressing spurious components in the frequency band equal to or higher than the anti-resonant frequency can be confirmed.

[0083] The experimental measurement results are listed in the following table.

[0084]

Table 1

[0085]

[0086]

[0087] *1) Limited effect: No effect near the anti-resonance frequency, but significant effect in higher frequency regions

[0088] When the width of the dummy electrode is arranged within a range of 20% to 80% of the width of the IDT electrode, an effect of suppressing spurious components in a frequency band equal to or higher than the anti-resonance frequency Fa can be confirmed.

[0089] In this case, when the width of the dummy electrode is represented as Td and the width of the IDT electrode is represented as Tp, Td and Tp can be represented by the following equation.

[0090] (0.2×Tp) <Td<(0.8×Tp)

[0091] However, when the width of the dummy electrode is 20% to 50% of the width of the IDT electrode, it can be understood that there is an effect of suppressing spurious components in the frequency band higher than the antiresonance frequency Fa, but the suppression of spurious components deteriorates in the frequency band between the resonance frequency Fr and the antiresonance frequency Fa.

[0092] This situation can be applied in high-frequency circuit design when it is necessary to selectively reduce spurious components in a specific frequency band equal to or higher than the anti-resonance frequency. This is because the input frequency band of the front end of high-frequency application equipment has become wider recently, and it may be necessary to reduce spurious components at this specific frequency.

[0093] In order to obtain an improved effect on the suppression of spurious components in all frequency bands equal to or higher than the resonance frequency Fr, the width of the dummy electrode may be configured to be within a range of 50% to 80% of the width of the IDT electrode.

[0094] In the portion where the width of the dummy electrode is within the range of 20% to 50% of the width of the IDT electrode, the suppression of spurious components can be improved in the frequency band equal to or higher than the anti-resonance frequency Fa, but may deteriorate at certain frequencies in the frequency band between the resonance frequency Fr and the anti-resonance frequency Fa. Therefore, it is necessary to exclude these frequencies.

[0095] In this case, when the width of the dummy electrode is represented as Td and the width of the IDT electrode is represented as Tp, the relationship between Td and Tp can be represented by the following equation.

[0096] (0.5×Tp) <Td<(0.8×Tp)

[0097] As described above, according to the surface acoustic wave filter for suppressing stray components caused by the transverse mode of the present disclosure, it is possible to configure such that the acoustic velocity at the dummy electrode is higher than the acoustic velocity at the IDT electrode. Therefore, it is possible to suppress stray components caused by unnecessary transverse modes and solve the insertion loss in the frequency band higher than the anti-resonance frequency.

[0098] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it will be understood by those skilled in the art that the present disclosure may be implemented in other specific forms without changing the technical spirit or basic features.

[0099] The scope of the present disclosure is basically determined by the scope defined by the appended claims, but includes not only the configurations directly derived from the claims, but also all changes or modifications within the scope of the claims and their equivalents should be construed as being included in the present disclosure.

Claims

1. A surface acoustic wave filter for suppressing stray components caused by a transverse mode, the surface acoustic wave filter comprising: a substrate on which a supporting substrate, an energy confinement layer and a piezoelectric layer are sequentially stacked; a first bus bar and a second bus bar extending along a first direction on the substrate and spaced apart from each other in a second direction perpendicular to the first direction; a plurality of first IDT electrodes and a plurality of second IDT electrodes, which extend alternately from the first bus bar and the second bus bar along the second direction and are spaced apart from each other in the first direction; a second dummy electrode extending from the second bus bar to face an end portion of each of the plurality of first IDT electrodes extending from the first bus bar; as well as a first dummy electrode extending from the first bus bar to face an end portion of each of a plurality of second IDT electrodes extending from the second bus bar, The acoustic velocity at the first dummy electrode and the second dummy electrode is higher than the acoustic velocity at the plurality of first IDT electrodes and second IDT electrodes.

2. A surface acoustic wave filter for suppressing stray components caused by a transverse mode, the surface acoustic wave filter comprising: a substrate on which a supporting substrate, an energy confinement layer and a piezoelectric layer are sequentially stacked; a first bus bar and a second bus bar extending along a first direction on the substrate and spaced apart from each other in a second direction perpendicular to the first direction; a plurality of first IDT electrodes and a plurality of second IDT electrodes, which extend alternately from the first bus bar and the second bus bar along the second direction and are spaced apart from each other in the first direction; a second dummy electrode extending from the second bus bar to face an end portion of each of the plurality of first IDT electrodes extending from the first bus bar; as well as a first dummy electrode extending from the first bus bar to face an end portion of each of a plurality of second IDT electrodes extending from the second bus bar, Among them, the spurious components are suppressed in the frequency band higher than the anti-resonance frequency.

3. A surface acoustic wave filter for suppressing stray components caused by a transverse mode, the surface acoustic wave filter comprising: a substrate on which a supporting substrate, an energy confinement layer and a piezoelectric layer are sequentially stacked; a first bus bar and a second bus bar extending along a first direction on the substrate and spaced apart from each other in a second direction perpendicular to the first direction; a plurality of first IDT electrodes and a plurality of second IDT electrodes, which extend alternately from the first bus bar and the second bus bar along the second direction and are spaced apart from each other in the first direction; a second dummy electrode extending from the second bus bar to face an end portion of each of the plurality of first IDT electrodes extending from the first bus bar; as well as a first dummy electrode extending from the first bus bar to face an end portion of each of a plurality of second IDT electrodes extending from the second bus bar, Among them, the spurious components are suppressed in the frequency band higher than the resonance frequency.

4. The surface acoustic wave filter according to any one of claims 1 to 3, wherein: The width of each of the first and second dummy electrodes is smaller than the width of each of the plurality of first and second IDT electrodes.

5. The surface acoustic wave filter according to claim 1 or 2, wherein: The width of each of the first dummy electrode and the second dummy electrode is configured to be within a range of 20% to 80% of the width of each of the plurality of first and second IDT electrodes.

6. The surface acoustic wave filter according to claim 1 or 3, wherein: The width of each of the first dummy electrode and the second dummy electrode is configured to be within a range of 50% to 80% of the width of each of the plurality of first and second IDT electrodes.

7. The surface acoustic wave filter according to any one of claims 1 to 3, wherein: The density of each of the first dummy electrodes and the second dummy electrodes is higher than the density of each of the plurality of first and second IDT electrodes.

8. The surface acoustic wave filter according to any one of claims 1 to 3, wherein: In both sides of a region where the plurality of first IDT electrodes and the plurality of second IDT electrodes exist simultaneously in the second direction and are spaced apart from each other in the first direction, edge portions having a sound velocity lower than that of the central portion are provided.

9. The surface acoustic wave filter according to claim 8, wherein: The width of the edge portion is greater than the width of each of the plurality of first and second IDT electrodes.

10. The surface acoustic wave filter according to claim 8, wherein The density of the edge portion is lower than that of each of the plurality of first and second IDT electrodes.

11. The surface acoustic wave filter according to claim 8, wherein The edge portion is formed by adding a mass adding film to the plurality of first IDT electrodes and second IDT electrodes.

12. The surface acoustic wave filter according to claim 11, wherein The density of the mass-added film is equal to or less than 5g / cm 3 .

13. The surface acoustic wave filter according to claim 11, wherein The mass-added film includes at least one selected from silicon dioxide (SiO2), tantalum pentoxide (Ta2O5), and aluminum oxide (Al2O3).

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