Elastic wave filter

Abstract

An elastic wave filter (1) comprises: a substrate (10) that includes a piezoelectric layer (104); a resonator (S22) that is disposed on the piezoelectric layer (104) and has a plurality of curved electrode fingers arranged side-by-side in the y direction; and a ground terminal (13a). The plurality of curved electrode fingers of the resonator (S22) include curved electrode fingers (S2221 and S2232) located at both ends of the resonator in the y direction. The ground terminal (13a) is located closer to the curved electrode finger (S2221) as compared with the curved electrode finger (S2232), and, in a plan view of the substrate (10), at least one of a plurality of normal lines (V2221) to the extension direction of the curved electrode finger (S2221) intersects with the ground terminal (13a).

Description

Acoustic Wave Filter

[0001] The present invention relates to an acoustic wave filter.

[0002] Japanese Patent Application Laid-Open No. 2003-144999 discloses an acoustic wave filter that is miniaturized by removing a part of a reflector and arranging a bump close to the removed part.

[0003] Japanese Patent Application Laid-Open No. 2012-5018

[0004] However, in conventional acoustic wave filters, it may be difficult to suppress unwanted responses caused by acoustic wave components leaking from the resonators.

[0005] Therefore, the present invention provides an acoustic wave filter that can suppress unwanted responses caused by acoustic wave components leaking from a resonator.

[0006] An acoustic wave filter according to one aspect of the present invention comprises a substrate including a piezoelectric layer, a first resonator arranged on the piezoelectric layer and having a plurality of curved electrode fingers aligned in a first direction, and a first external connection terminal, wherein the plurality of curved electrode fingers of the first resonator include first curved electrode fingers and second curved electrode fingers located at both ends in the first direction, the first external connection terminal is closer to the first curved electrode fingers than the second curved electrode fingers, and at least one of a plurality of first normals to the extension direction of the first curved electrode fingers intersects with the first external connection terminal in a planar view of the substrate.

[0007] An acoustic wave filter according to one aspect of the present invention comprises a substrate including a piezoelectric layer, a resonator arranged on the piezoelectric layer and having a plurality of curved electrode fingers, and an external connection terminal, wherein the normal to the center line extending in the extension direction at the tip of at least one of the plurality of curved electrode fingers of the resonator intersects with the external connection terminal in a planar view of the substrate.

[0008] An acoustic wave filter according to one aspect of the present invention comprises a substrate including a piezoelectric layer, a first resonator arranged on the piezoelectric layer and having a plurality of curved electrode fingers aligned in a first direction, and a first external connection terminal, wherein the plurality of curved electrode fingers of the first resonator include first curved electrode fingers and second curved electrode fingers having lengths equal to an average length of the curved electrode fingers arranged in a central region of the first resonator in the first direction, the first curved electrode finger and the second curved electrode finger being two curved electrode fingers at opposite ends in the first direction among two or more curved electrode fingers having lengths equal to the average length included in the plurality of curved electrode fingers of the first resonator, the first external connection terminal being closer to the first curved electrode finger than the second curved electrode finger, and at least one of a plurality of first normals to the extension direction of the first curved electrode finger intersects the first external connection terminal in a plan view of the substrate.

[0009] According to the present invention, it is possible to suppress unwanted responses caused by elastic wave components leaking from a resonator.

[0010] FIG. 1 is a circuit diagram of an elastic wave filter according to a first embodiment. FIG. 2 is a plan view of the elastic wave filter according to the first embodiment. FIG. 3A is an example of a partial cross-sectional view of the elastic wave filter according to the first embodiment. FIG. 3B is an example of a partial cross-sectional view of the elastic wave filter according to the first embodiment. FIG. 4 is a partial plan view of the elastic wave filter according to the first embodiment. FIG. 5 is an enlarged plan view of curved electrode fingers of the elastic wave filter according to the first embodiment. FIG. 6 is a partial plan view of the elastic wave filter according to the first embodiment. FIG. 7 is a partial plan view of the elastic wave filter according to the first embodiment. FIG. 8 is a partial plan view of an elastic wave filter according to a first modification of the first embodiment. FIG. 9 is a partial plan view of an elastic wave filter according to a second modification of the first embodiment. FIG. 10 is a partial plan view of an elastic wave filter according to a third modification of the first embodiment. FIG. 11 is a partial plan view of the elastic wave filter according to the second embodiment. FIG. 12 is a partial plan view of an elastic wave filter according to another embodiment. FIG. 13 is a partial plan view of an elastic wave filter according to another embodiment. FIG. 14 is a plan view of a resonator according to another embodiment. Fig. 15A is a diagram for explaining a procedure for reading the shape of the electrode fingers from an actual resonator. Fig. 15B is a diagram for explaining a procedure for reading the shape of the electrode fingers from an actual resonator. Fig. 15C is a diagram for explaining a procedure for reading the shape of the electrode fingers from an actual resonator. Fig. 15D is a diagram for explaining a procedure for reading the shape of the electrode fingers from an actual resonator.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0012] It should be noted that the drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present invention, and are not necessarily strictly illustrated, and may differ from the actual shapes, positional relationships, and proportions. In the drawings, the same reference numerals are used to denote substantially the same components, and redundant explanations may be omitted or simplified.

[0013] In the following drawings, the x-axis and y-axis are axes that are perpendicular to each other on a plane parallel to the main surface of the substrate, and the z-axis is an axis perpendicular to the main surface of the substrate, with its positive direction indicating the upward direction and its negative direction indicating the downward direction.

[0014] In the following description, "connected" includes not only direct connection by a connection terminal and / or wiring conductor, but also electrical connection via other circuit elements. "Directly connected" means direct connection by a connection terminal and / or wiring conductor without via other circuit elements. "C is connected between A and B" means that one end of C is connected to A and the other end of C is connected to B, and C is arranged in series on the path connecting A and B. "Path connecting A and B" means a path made up of a conductor electrically connecting A to B.

[0015] "Planar view of the substrate" means that the object is viewed by orthogonally projecting it onto the xy plane in the negative direction of the z axis. "A overlaps with B in planar view" means that the area of ​​A orthogonally projected onto the xy plane overlaps with the area of ​​B orthogonally projected onto the xy plane.

[0016] "A is located between B and C" means that at least one of multiple line segments connecting any point in B and any point in C passes through A. "A is closer to C than B" means that the distance between A and C is shorter than the distance between B and C. Here, "the distance between A (B) and C" means the length of the shortest line segment among multiple line segments connecting any point in A (B) and any point in C.

[0017] The term "curved electrode finger" refers to an electrode finger whose extension direction is at least partially curved in a plan view. For example, the curved electrode finger is an electrode finger that extends along a smooth curve. Alternatively, for example, the curved electrode finger may be an electrode finger that extends along a non-smooth curve (e.g., a curve that includes a bend). Alternatively, for example, the curved electrode finger may be an electrode finger that extends along a combination of a curve and a straight line.

[0018] The "plurality of normal lines to the extension direction of the curved electrode fingers" refers to a set of local normal lines to a curve (center line) connecting the centers of the curved electrode fingers in the width direction. More specifically, the "plurality of normal lines to the extension direction of the curved electrode fingers" refers to a set of n+1 straight lines (n is an integer greater than 2) that are locally perpendicular to the center line at n equal dividing points (including both end points) of the center line of the curved electrode fingers.

[0019] Furthermore, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "straight line," and numerical ranges do not only represent the strict meaning, but also include a substantially equivalent range, for example, an error of a few percent.

[0020] (First Embodiment) A first embodiment will be described.

[0021] [1.1. Circuit Configuration of Acoustic Wave Filter 1] The circuit configuration of an acoustic wave filter 1 according to this preferred embodiment will be specifically described with reference to Fig. 1. Fig. 1 is a circuit configuration diagram of an acoustic wave filter 1 according to this preferred embodiment.

[0022] 1 is an exemplary circuit configuration, and the acoustic wave filter 1 can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the following description of the acoustic wave filter 1 should not be construed as limiting. Furthermore, curved electrode fingers can be applied not only to a resonator having an IDT and reflectors at both ends of the IDT, but also to a longitudinally coupled filter having multiple IDT regions.

[0023] The acoustic wave filter 1 is a ladder-type surface acoustic wave (SAW) filter and includes input / output terminals 11 and 12, a ground terminal 13, and resonators S1, S2, S3, S4, P1, P2, P3, and P4.

[0024] The input / output terminal 11 is an external connection terminal of the acoustic wave filter 1 and is connected to a power amplifier (PA) and / or a low noise amplifier (LNA) outside the acoustic wave filter 1. The input / output terminal 11 is connected to the resonator S1 inside the acoustic wave filter 1.

[0025] The input / output terminal 12 is an external connection terminal of the acoustic wave filter 1 and is connected to an antenna (ANT) outside the acoustic wave filter 1. The input / output terminal 12 is connected to the resonator S4 inside the acoustic wave filter 1.

[0026] The ground terminal 13 is an external connection terminal of the acoustic wave filter 1 and is connected to ground (GND) outside the acoustic wave filter 1. The ground terminal 13 is connected to the resonators P1, P2, P3, and P4 inside the acoustic wave filter 1. The four ground terminals 13 may be integrated in any combination.

[0027] The resonator S1 is a series arm resonator connected between the input / output terminal 11 and the resonator S2. The resonator S1 includes three resonators S11, S12, and S13 connected in series.

[0028] The resonator S2 is a series arm resonator connected between the resonators S1 and S3, and includes two resonators S21 and S22 connected in series.

[0029] The resonator S3 is a series arm resonator connected between the resonators S2 and S4, and includes two resonators S31 and S32 connected in series.

[0030] The resonator S4 is a series arm resonator connected between the resonator S3 and the input / output terminal 12. The resonator S4 includes three resonators S41, S42, and S43 connected in series.

[0031] The resonator P1 is a parallel arm resonator connected between a path connecting the input / output terminal 11 and the resonator S1 and the ground terminal 13. The resonator P1 includes two resonators P11 and P12 connected in series.

[0032] The resonator P2 is a parallel arm resonator connected between the path connecting the resonators S1 and S2 and the ground terminal 13. The resonator P2 includes a resonator P21.

[0033] The resonator P3 is a parallel arm resonator connected between the path connecting the resonators S2 and S3 and the ground terminal 13. The resonator P3 includes a resonator P31.

[0034] The resonator P4 is a parallel arm resonator connected between the path connecting the resonators S3 and S4 and the ground terminal 13. The resonator P4 includes a resonator P41.

[0035] At least one of the resonators S11, S12, S13, S21, S22, S31, S32, S41, S42, S43, P11, P12, P21, P31 and P41 is an acoustic wave resonator having a plurality of curved electrode fingers.

[0036] 1 is an example, and the circuit configuration of the acoustic wave filter 1 is not limited to that shown in FIG. 1. For example, the number of resonators included in the acoustic wave filter 1 is not limited to eight, and may be seven or less, or nine or more. Furthermore, for example, in FIG. 1, a capacitor and / or an inductor may be connected between two adjacent resonators or between a resonator and a terminal.

[0037] [1.2. Structure of Acoustic Wave Filter 1] Next, the structure of the acoustic wave filter 1 will be described in detail with reference to FIGS. 2, 3A, and 3B. FIG. 2 is a plan view of the acoustic wave filter 1 according to this preferred embodiment. Note that the sealing material 15 is omitted from the plan view of FIG. 2 to facilitate understanding of the arrangement of the resonators on the substrate 10 (this also applies to the subsequent plan views). FIG. 3A is an example of a partial cross-sectional view of the acoustic wave filter 1 according to this preferred embodiment. FIG. 3B is another example of a partial cross-sectional view of the acoustic wave filter 1 according to this preferred embodiment. The cross sections of the acoustic wave filter 1 in FIGS. 3A and 3B are taken along line iii-iii in FIG. 2. FIGS. 3A and 3B show cross-sectional structures of the acoustic wave filter 1 that can be arbitrarily selected.

[0038] 2, 3A, and 3B are examples of typical structures of the acoustic wave filter 1, and the structure of the acoustic wave filter 1 is not limited to the structures shown in Fig. 2, 3A, and 3B. Therefore, the following description of the acoustic wave filter 1 should not be interpreted in a limiting sense.

[0039] As shown in FIG. 2 and FIG. 3A or FIG. 3B, the acoustic wave filter 1 includes a substrate 10, a pad electrode 14, and a sealing material 15 in addition to the circuit elements shown in FIG.

[0040] The substrate 10 includes a support substrate 101 , a high acoustic velocity layer 102 , a low acoustic velocity layer 103 , and a piezoelectric layer 104 .

[0041] The support substrate 101 can support the high acoustic velocity layer 102, the low acoustic velocity layer 103, and the piezoelectric layer 104. Examples of materials that can be used for the support substrate 101 include piezoelectric materials such as silicon nitride, aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectric materials such as diamond and glass; semiconductors such as silicon and gallium nitride; resins; and any combinations of these. Note that the material of the support substrate 101 is not limited to these.

[0042] The high acoustic velocity layer 102 is laminated on the support substrate 101 and disposed between the low acoustic velocity layer 103 and the support substrate 101. The high acoustic velocity layer 102 confines the surface acoustic waves generated by the resonator within the area where the piezoelectric layer 104 and the low acoustic velocity layer 103 are laminated, preventing them from leaking to layers below the high acoustic velocity layer 102. The acoustic velocity of bulk waves propagating through the high acoustic velocity layer 102 is faster than the acoustic velocity of acoustic waves, such as surface waves and boundary waves, propagating through the piezoelectric layer 104. Examples of materials that can be used for the high acoustic velocity layer 102 include piezoelectric materials such as silicon nitride, aluminum nitride, lithium tantalate, lithium niobate, and quartz; ceramics such as alumina, sapphire, magnesia, silicon carbide, zirconia, cordierite, mullite, steatite, and forsterite; dielectrics such as diamond and glass; semiconductors such as silicon and gallium nitride; resins; and any combination thereof. Note that the material of the high acoustic velocity layer 102 is not limited to these.

[0043] The high acoustic velocity layer 102 and the support substrate 101 may be integrated into a single high acoustic velocity support substrate. Examples of materials that can be used for the high acoustic velocity support substrate include piezoelectric materials such as aluminum nitride, lithium tantalate, lithium niobate, and quartz crystal; ceramic materials such as alumina, sapphire, magnesia, silicon nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, spinel group materials, and sialon; dielectric materials such as aluminum oxide, silicon oxynitride, DLC (diamond-like carbon), and diamond; semiconductor materials such as silicon; and any combinations of these materials. The spinel group includes aluminum compounds containing oxygen and one or more elements selected from magnesium, iron, zinc, manganese, and the like. Specific examples include spinel (MgAl ２ O ４ ), hercynite (FeAl ２ O ４ ), Gahnite (ZnAl ２ O ４ ), and galactite (MnAl ２ O ４ ) are listed.

[0044] The low acoustic velocity layer 103 is laminated on the high acoustic velocity layer 102 and is disposed between the piezoelectric layer 104 and the high acoustic velocity layer 102. The acoustic velocity of bulk waves propagating through the low acoustic velocity layer 103 is slower than the acoustic velocity of elastic waves, such as surface waves and boundary waves, propagating through the piezoelectric layer 104. The low acoustic velocity layer 103 can be made of a dielectric material such as silicon dioxide, glass, silicon oxynitride, lithium oxide, tantalum oxide, or a compound in which fluorine, carbon, or boron is added to silicon oxide, or any combination of these. Note that the material of the low acoustic velocity layer 103 is not limited to these.

[0045] The piezoelectric layer 104 is a layer having piezoelectricity laminated on the low acoustic velocity layer 103, and is capable of propagating surface acoustic waves. Resonators S11, S12, S13, S21, S22, S31, S32, S41, S42, S43, P11, P12, P21, P31, and P41 are arranged on the piezoelectric layer 104. The piezoelectric layer 104 is made of, for example, lithium tantalate (LiTaO ３), lithium niobate (LiNbO ３ ), aluminum nitride, or zinc oxide piezoelectric single crystal or piezoelectric ceramics can be used.

[0046] The resonators S1, S2, S3, S4, P1, P2, P3, and P4 are disposed on a major surface of the piezoelectric layer 104. Each of the resonators S11, S12, S13, S21, S22, S31, S32, S41, S42, S43, P11, P12, P21, P31, and P41 included in the resonators S1, S2, S3, S4, P1, P2, P3, and P4 includes an interdigital transducer (IDT) and a reflector.

[0047] In this embodiment, resonator S22 included in resonator S2, resonator P31 included in resonator P3, and resonators S41, S42, and S43 included in resonator S4 each have a plurality of curved electrode fingers, while the remaining resonators S11, S12, S13, S21, S31, S32, P11, P12, P21, and P41 each have a plurality of non-curved electrode fingers. Non-curved electrode fingers refer to electrode fingers that do not extend in a curved direction in a planar view. In other words, non-curved electrode fingers refer to electrode fingers that extend in a straight direction in a planar view. Note that the combination of resonators having a plurality of curved electrode fingers is not limited to the combination shown in FIG. 2 (resonators S22, P31, S41, S42, and S43).

[0048] Each of the input / output terminals 11 and 12 and the ground terminal 13 includes a bump electrode and a via conductor, and is disposed on the substrate 10. The ground terminal 13 includes a bump electrode 131 and a via conductor 132, as shown in FIG. 3A or 3B.

[0049] The bump electrode 131 is exposed from the sealing material 15 and is connected to a ground terminal of a module substrate (not shown). The material of the bump electrode 131 may be, for example, solder, but other metals (for example, copper, gold, aluminum, etc.) may also be used.

[0050] The via conductor 132 electrically connects the bump electrode 131 to the pad electrode 14. The material of the via conductor 132 can be copper, but other metals (for example, gold, aluminum, etc.) may also be used.

[0051] The bump electrodes and via conductors of the input / output terminals 11 and 12 are similar to those of the ground terminal 13, and therefore illustration and description thereof will be omitted.

[0052] The pad electrodes 14 electrically connect the resonators S1, S2, S3, S4, P1, P2, P3, and P4 to the input / output terminals 11 and 12 and the ground terminal 13. The pad electrodes 14 may be made of copper, but other metals (e.g., gold, aluminum, etc.) may also be used.

[0053] The sealing material 15 is a member for forming and sealing spaces above the resonators S1, S2, S3, S4, P1, P2, P3, and P4. The sealing material 15 covers the side and top surfaces of the spaces above the resonators S1, S2, S3, S4, P1, P2, P3, and P4, and also covers the areas of the input / output terminals 11 and 12 and the ground terminal 13. The material for the sealing material 15 can be, but is not limited to, a resin.

[0054] 2, 3A, or 3B is merely an example, and is not limited to the structure of the acoustic wave filter 1. For example, the substrate 10 may not include the support substrate 101, the high acoustic velocity layer 102, or the low acoustic velocity layer 103, and may include only the piezoelectric layer 104. In this case, a hollow structure may be formed on the back surface of the region of the piezoelectric layer 104 where the resonators are formed.

[0055] Furthermore, for example, the substrate 10 may include a multilayer reflective film in which high-impedance layers and low-impedance layers whose specific acoustic impedance is lower than that of the high-impedance layers are alternately stacked, instead of the high acoustic velocity layer 102. Even in this case, the surface acoustic waves can be confined within the piezoelectric layer 104, thereby preventing the surface acoustic waves from leaking to the outside.

[0056] Furthermore, for example, an IDT or a planar electrode may be formed on the main surface of the piezoelectric layer 104 opposite to the main surface on which the resonators are formed.

[0057] [1.3. Positional Relationship Between the Resonators S22 and P31 and the Ground Terminal 13] Next, the positional relationship between the resonators S22 and P31 and the ground terminal 13 will be described with reference to FIGS. 2 and 4 to 6. FIG.

[0058] 4 and 6 are partial plan views of the acoustic wave filter 1 according to this preferred embodiment. The portions of the acoustic wave filter 1 shown in FIGS. 4 and 6 correspond to the portions indicated by regions iv and vi in ​​FIG. 2. FIG. 5 is an enlarged plan view of curved electrode fingers S2221 of the acoustic wave filter 1 according to this preferred embodiment.

[0059] 4 to 6 are examples of the positional relationship between the resonators S22 and P31 and the ground terminal 13, and the positional relationship between the resonators S22 and P31 and the ground terminal 13 is not limited to the positional relationship shown in Figures 4 to 6. Therefore, the following description of the resonators S22 and P31 and the ground terminal 13 should not be interpreted in a restrictive manner.

[0060] In the following description, in order to distinguish between the ground terminal 13 in FIG. 4 and the ground terminal 13 in FIG. 6, the ground terminal 13 in FIG. 4 will be referred to as a ground terminal 13a, and the ground terminal 13 in FIG. 6 will be referred to as a ground terminal 13b.

[0061] The resonator S22 is an example of a first resonator and includes an IDTS221 and reflectors S222 and S223, each having a plurality of curved electrode fingers aligned in the y direction (first direction). The IDTS221 is disposed between the reflectors S222 and S223 in the y direction. The plurality of curved electrode fingers of the resonator S22 include curved electrode fingers S2221 and S2232 located at both ends in the y direction.

[0062] The curved electrode finger S2221 is an example of a first curved electrode finger and is included in the reflector S222. The curved electrode finger S2221 is arranged near the ground terminal 13a. In a plan view of the substrate 10, the curved electrode finger S2221 is curved such that a central portion in the extension direction of the curved electrode finger S2221 is curved away from the ground terminal 13a. In other words, the curved electrode finger S2221 has a convex shape that is convex in a direction away from the ground terminal 13a.

[0063] The curved electrode finger S2232 is an example of a second curved electrode finger and is included in the reflector S223. The curved electrode finger S2232 is arranged near the ground terminal 13b. In a plan view of the substrate 10, the curved electrode finger S2232 is curved such that the center portion approaches the ground terminal 13b in the extension direction of the curved electrode finger S2232. In other words, the curved electrode finger S2232 has a convex shape in the direction approaching the ground terminal 13b.

[0064] The ground terminal 13a is an example of a first external connection terminal and is closer to the curved electrode finger S2221 than to the curved electrode finger S2232. The ground terminal 13b is an example of a second external connection terminal and is closer to the curved electrode finger S2232 than to the curved electrode finger S2221.

[0065] The multiple normal lines V2221 are an example of multiple first normal lines and are a collection of straight lines that are locally perpendicular to the center line X2221 of the curved electrode finger S2221. Note that the arrows attached to the multiple normal lines V2221 indicate the direction of leakage of acoustic waves. In FIG. 4 , in a plan view of the substrate 10, all of the multiple normal lines V2221 intersect with the ground terminal 13a. Note that only one of the multiple normal lines V2221 may intersect with the ground terminal 13a, preferably, one-half or more of the multiple normal lines V2221 may intersect with the ground terminal 13a, and more preferably, three-quarters or more of the multiple normal lines V2221 may intersect with the ground terminal 13a.

[0066] The multiple normal lines V2232 are an example of multiple second normal lines and are a collection of straight lines that are locally perpendicular to the center line of the curved electrode finger S2232. Note that the arrows attached to the multiple normal lines V2232 indicate the direction of leakage of acoustic waves. In FIG. 6 , in a plan view of the substrate 10, all of the multiple normal lines V2232 intersect with the ground terminal 13b. Note that only one of the multiple normal lines V2232 may intersect with the ground terminal 13b, preferably, one-half or more of the multiple normal lines V2232 may intersect with the ground terminal 13b, and more preferably, three-quarters or more of the multiple normal lines V2232 may intersect with the ground terminal 13b.

[0067] The resonator P31 is an example of a second resonator and is arranged adjacent to the resonator S22 in the x direction. The resonator P31 includes an IDTP311 and reflectors P312 and P313, each having a plurality of curved electrode fingers aligned in the y direction. The IDTP311 is arranged between the reflectors P312 and P313 in the y direction. The plurality of curved electrode fingers of the resonator P31 include curved electrode fingers P3121 and P3132 located at both ends in the y direction.

[0068] The curved electrode finger P3121 is an example of a third curved electrode finger and is included in the reflector P312. The curved electrode finger P3132 is an example of a fourth curved electrode finger and is included in the reflector P313. The curved electrode finger P3121 is arranged near the ground terminal 13a. In a plan view of the substrate 10, the curved electrode finger P3121 is curved so that the center portion in the extension direction of the curved electrode finger P3121 is away from the ground terminal 13a. In other words, the curved electrode finger P3121 has a convex shape in the direction away from the ground terminal 13a. The ground terminal 13a is closer to the curved electrode finger P3121 than to the curved electrode finger P3132.

[0069] The multiple normal lines V3121 are an example of multiple third normal lines and are a collection of straight lines that are locally perpendicular to the center line of the curved electrode finger P3121. Note that the arrows attached to the multiple normal lines V3121 indicate the direction of leakage of acoustic waves. In FIG. 4 , in a plan view of the substrate 10, some of the multiple normal lines V3121 intersect with the ground terminal 13a. Note that only one of the multiple normal lines V3121 may intersect with the ground terminal 13a, preferably, one-half or more of the multiple normal lines V3121 may intersect with the ground terminal 13a, more preferably, three-quarters or more of the multiple normal lines V3121 may intersect with the ground terminal 13a, and even more preferably, all of the multiple normal lines V3121 may intersect with the ground terminal 13a.

[0070] 4 and 6, the number of the plurality of normals V2221, the number of the plurality of normals V2232, and the number of the plurality of normals V3121 are each 5, but this is not limited to this. The number of the plurality of normals V2221, the number of the plurality of normals V2232, and the number of the plurality of normals V3121 may be 4, 6, 7, 8, 9, 10, or more.

[0071] [1.4. Positional Relationship Between Resonators S41, S42, and S43 and Input / Output Terminal 12] Next, the positional relationship between the resonators S22 and P31 and the input / output terminal 12 will be described with reference to FIGS.

[0072] 7 is a partial plan view of the acoustic wave filter 1 according to this preferred embodiment. The portion of the acoustic wave filter 1 shown in FIG. 7 is the portion indicated by region vii in FIG.

[0073] 7 is an example of the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12, and the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12 is not limited to the positional relationship shown in FIG. 7. Therefore, the following description of the resonators S41, S42, and S43 and the input / output terminals 12 should not be interpreted in a restrictive manner.

[0074] The resonator S43 is an example of a first resonator and includes an IDTS431 and reflectors S432 and S433, each having a plurality of curved electrode fingers aligned in the y direction. The IDTS431 is disposed between the reflectors S432 and S433 in the y direction. The curved electrode fingers of the resonator S43 include curved electrode fingers S4321 and S4332 at both ends in the y direction.

[0075] The curved electrode finger S4321 is an example of a first curved electrode finger and is included in the reflector S432. The curved electrode finger S4332 is an example of a second curved electrode finger and is included in the reflector S433. The curved electrode finger S4321 is arranged near the input / output terminal 12. In a plan view of the substrate 10, the curved electrode finger S4321 is curved such that a central portion in the extension direction of the curved electrode finger S4321 is curved away from the input / output terminal 12. In other words, the curved electrode finger S4321 has a convex shape in a direction away from the input / output terminal 12. The input / output terminal 12 is an example of a first external connection terminal and is closer to the curved electrode finger S4321 than to the curved electrode finger S4332.

[0076] The multiple normal lines V4321 are an example of multiple first normal lines and are a collection of straight lines that are locally perpendicular to the center line of the curved electrode finger S4321. Note that the arrows attached to the multiple normal lines V4321 indicate the direction of leakage of acoustic waves. In FIG. 7 , in a plan view of the substrate 10, all of the multiple normal lines V4321 intersect with the input / output terminal 12. Note that only one of the multiple normal lines V4321 may intersect with the input / output terminal 12, preferably, one-half or more of the multiple normal lines V4321 may intersect with the input / output terminal 12, and more preferably, three-quarters or more of the multiple normal lines V4321 may intersect with the input / output terminal 12.

[0077] The resonator S42 is an example of a second resonator and is arranged adjacent to the resonator S43 in the x direction. The resonator S42 includes an IDTS421 and reflectors S422 and S423, each having a plurality of curved electrode fingers aligned in the y direction. The IDTS421 is arranged between the reflectors S422 and S423 in the y direction. The plurality of curved electrode fingers of the resonator S42 include curved electrode fingers S4221 and S4232 located at both ends in the y direction.

[0078] The curved electrode finger S4221 is an example of a third curved electrode finger and is included in the reflector S422. The curved electrode finger S4232 is an example of a fourth curved electrode finger and is included in the reflector S423. The curved electrode finger S4221 is arranged near the input / output terminal 12. In a plan view of the substrate 10, the curved electrode finger S4221 is curved such that a central portion in the extension direction of the curved electrode finger S4221 is curved away from the input / output terminal 12. In other words, the curved electrode finger S4221 has a convex shape in a direction away from the input / output terminal 12. The input / output terminal 12 is closer to the curved electrode finger S4221 than to the curved electrode finger S4232.

[0079] The multiple normal lines V4221 are an example of multiple third normal lines and are a collection of straight lines that are locally perpendicular to the center line of the curved electrode finger S4221. Note that the arrows attached to the multiple normal lines V4221 indicate the direction of leakage of acoustic waves. In FIG. 7 , in a plan view of the substrate 10, some of the multiple normal lines V4221 intersect the input / output terminal 12. Note that only one of the multiple normal lines V4221 may intersect the input / output terminal 12, preferably, one-half or more of the multiple normal lines V4221 may intersect the input / output terminal 12, more preferably, three-quarters or more of the multiple normal lines V4221 may intersect the input / output terminal 12, and even more preferably, all of the multiple normal lines V4221 may intersect the input / output terminal 12.

[0080] The resonator S41 includes an IDTS 411 and a reflector S412, each having a plurality of curved electrode fingers arranged in the y direction. The curved electrode finger S4121 is included in the reflector S412. In this embodiment, in a plan view of the substrate 10, none of the plurality of normals V4121 to the curved electrode finger S4121 intersects with the input / output terminal 12.

[0081] [1.5. Summary] As described above, the acoustic wave filter 1 according to this embodiment includes a substrate 10 including a piezoelectric layer 104, a resonator S22 disposed on the piezoelectric layer 104 and having a plurality of curved electrode fingers aligned in the y direction, and a ground terminal 13a, wherein the plurality of curved electrode fingers of the resonator S22 include curved electrode fingers S2221 and S2232 located at both ends in the y direction, the ground terminal 13a is closer to the curved electrode finger S2221 than to the curved electrode finger S2232, and at least one of the plurality of normals V2221 of the curved electrode finger S2221 intersects with the ground terminal 13a in a planar view of the substrate 10.

[0082] Because acoustic waves generated in the resonator S22 propagate in a direction normal to the extension direction of the curved electrode fingers, they tend to leak in the normal direction from the curved electrode finger S2221 at one end of the curved electrode fingers. The acoustic wave components leaking in the normal direction from the curved electrode finger S2221 may couple with and / or interfere with acoustic wave components of other adjacent resonators, resulting in unwanted responses, or may be multiple-reflected at the end of the acoustic wave filter 1, affecting standing waves in other resonators. Therefore, by having at least one of the normals V2221 of the curved electrode finger S2221 intersect with the ground terminal 13a, the acoustic wave components leaking in the normal direction from the curved electrode finger S2221 are effectively attenuated in the area of ​​the ground terminal 13a, thereby suppressing unwanted responses caused by the acoustic wave components leaking from the resonator S22. In particular, the area where external connection terminals such as the ground terminal 13a are provided is covered with the pad electrode 14 and the sealing material 15, which significantly attenuates the acoustic waves.

[0083] Furthermore, in acoustic wave filter 1 according to this preferred embodiment, curved electrode finger S2221 may be curved such that the center portion in the extension direction of curved electrode finger S2221 is away from ground terminal 13a in a plan view of substrate 10.

[0084] According to this, since the central portion in the extension direction of the curved electrode finger S2221 is curved so as to move away from the ground terminal 13a, components of acoustic waves leaking in the normal direction of the curved electrode finger S2221 tend to concentrate, causing unwanted responses. By having at least one of the multiple normals V2221 of such curved electrode finger S2221 intersect with the ground terminal 13a, unwanted responses can be more effectively suppressed.

[0085] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, half or more of the normal lines V2221 may intersect with the ground terminal 13a in a plan view of the substrate 10.

[0086] This allows the component of the elastic wave leaking from the resonator S22 to be attenuated more effectively in the area of ​​the ground terminal 13a, and thus makes it possible to more effectively suppress unwanted responses.

[0087] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, three-quarters or more of the normal lines V2221 may intersect with the ground terminal 13a in a plan view of the substrate 10.

[0088] This allows the component of the elastic wave leaking from the resonator S22 to be attenuated more effectively in the area of ​​the ground terminal 13a, and thus makes it possible to more effectively suppress unwanted responses.

[0089] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, all of the normal lines V2221 may intersect with the ground terminal 13a in a plan view of the substrate 10.

[0090] This allows the component of the elastic wave leaking from the resonator S22 to be attenuated more effectively in the area of ​​the ground terminal 13a, and thus makes it possible to more effectively suppress unwanted responses.

[0091] For example, the elastic wave filter 1 according to this embodiment may further include a ground terminal 13b that is closer to the curved electrode finger S2232 than to the curved electrode finger S2221, and at least one of the multiple normals V2232 of the curved electrode finger S2232 may intersect with the ground terminal 13b in a planar view of the substrate 10.

[0092] This allows the components of the acoustic waves leaking from the curved electrode finger S2232 at the end opposite to the curved electrode finger S2221 to be effectively attenuated in the area of ​​the ground terminal 13b, further suppressing unwanted responses.

[0093] Furthermore, in the acoustic wave filter 1 according to this preferred embodiment, the curved electrode finger S2232 may be curved such that the center portion of the curved electrode finger S2232 in the extension direction approaches the ground terminal 13b in a plan view of the substrate 10.

[0094] According to this, even if the central portion in the extension direction of the curved electrode finger S2232 is curved so as to approach the ground terminal 13b, the components of the elastic waves leaking in the normal direction of the curved electrode finger S2232 can be effectively attenuated in the area of ​​the ground terminal 13b, thereby suppressing unnecessary responses.

[0095] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, half or more of the normal lines V2232 may intersect with the ground terminal 13b in a plan view of the substrate 10.

[0096] This allows the elastic wave components leaking from the resonator S22 to be attenuated more effectively in the area of ​​the ground terminal 13b, thereby more effectively suppressing unwanted responses.

[0097] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, three-quarters or more of the normal lines V2232 may intersect with the ground terminal 13b in a plan view of the substrate 10.

[0098] This allows the elastic wave components leaking from the resonator S22 to be attenuated more effectively in the area of ​​the ground terminal 13b, thereby more effectively suppressing unwanted responses.

[0099] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, all of the normal lines V2232 may intersect with the ground terminal 13b in a plan view of the substrate 10.

[0100] This allows the elastic wave components leaking from the resonator S22 to be attenuated more effectively in the area of ​​the ground terminal 13b, thereby more effectively suppressing unwanted responses.

[0101] For example, the acoustic wave filter 1 according to this embodiment may further include a resonator P31 arranged on the piezoelectric layer 104 and having a plurality of curved electrode fingers aligned in the y direction, the plurality of curved electrode fingers of the resonator P31 may include curved electrode fingers P3121 and P3132 at both ends in the y direction, the ground terminal 13a may be closer to the curved electrode finger P3121 than to the curved electrode finger P3132, and at least one of the plurality of normals V3121 of the curved electrode finger P3121 may intersect with the ground terminal 13a in a planar view of the substrate 10.

[0102] This allows the component of the elastic wave leaking from the resonator P31, which is different from the resonator S22, to be attenuated in the area of ​​the ground terminal 13a, thereby suppressing unwanted responses.

[0103] Furthermore, in the acoustic wave filter 1 according to this preferred embodiment, the curved electrode finger P3121 may be curved such that the center portion in the extension direction of the curved electrode finger P3121 is away from the ground terminal 13a in a plan view of the substrate 10.

[0104] According to this, since the central portion in the extension direction of the curved electrode finger P3121 is curved so as to move away from the ground terminal 13a, components of acoustic waves leaking in the normal direction of the curved electrode finger P3121 tend to concentrate, causing unwanted responses. By having at least one of the multiple normals V3121 of such curved electrode finger P3121 intersect with the ground terminal 13a, unwanted responses can be more effectively suppressed.

[0105] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, half or more of the normal lines V3121 may intersect with the ground terminal 13a in a plan view of the substrate 10.

[0106] This allows the component of the elastic wave leaking from the resonator P31 to be attenuated more effectively in the area of ​​the ground terminal 13a, and thus allows unwanted responses to be suppressed more effectively.

[0107] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, three-quarters or more of the normal lines V3121 may intersect with the ground terminal 13a in a plan view of the substrate 10.

[0108] This allows the component of the elastic wave leaking from the resonator P31 to be attenuated more effectively in the area of ​​the ground terminal 13a, and thus allows unwanted responses to be suppressed more effectively.

[0109] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, all of the normal lines V3121 may intersect with the ground terminal 13a in a plan view of the substrate 10.

[0110] This allows the component of the elastic wave leaking from the resonator P31 to be attenuated more effectively in the area of ​​the ground terminal 13a, and thus allows unwanted responses to be suppressed more effectively.

[0111] Furthermore, for example, in the acoustic wave filter 1 according to this preferred embodiment, the resonators S22 and P31 may be arranged adjacent to each other in the x direction.

[0112] This allows acoustic waves leaking from the resonators S22 and P31 adjacent to each other in the x direction to be attenuated in the area of ​​the same ground terminal 13a, which contributes to miniaturization of the acoustic wave filter 1.

[0113] For example, in the acoustic wave filter 1 according to this embodiment, the resonator S22 may include a reflector S222 having curved electrode fingers S2221, a reflector S223 having curved electrode fingers S2232, and an IDTS221 arranged between the reflectors S222 and S223.

[0114] According to this, the reflectors S222 and S223 can suppress the acoustic waves leaking from the IDTS 221, and unwanted responses can be further suppressed.

[0115] (Variation 1 of Embodiment 1) Next, Variation 1 of Embodiment 1 will be described. In this variation, the main difference from Embodiment 1 is the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12. This variation will be described below with reference to FIG. 8, focusing on the differences from Embodiment 1.

[0116] 8 is a partial plan view of the acoustic wave filter 1 according to this modification. The portion of the acoustic wave filter 1 shown in FIG. 8 corresponds to the portion indicated by region vii in FIG.

[0117] 8 is an example of the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12, and the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12 is not limited to the positional relationship shown in Fig. 8. Therefore, the following description of the resonators S41, S42, and S43 and the input / output terminals 12 should not be interpreted in a restrictive manner.

[0118] In this modification, the input / output terminal 12 is disposed closer to the resonator S41 than in the first embodiment, and the left and right of the resonator S43 are reversed. As a result, in a plan view of the substrate 10, all of the multiple normals V4121 of the curved electrode fingers S4121 of the resonator S41 intersect the input / output terminal 12. Note that only one of the multiple normals V4121 may intersect the input / output terminal 12, preferably, one-half or more of the multiple normals V4121 may intersect the input / output terminal 12, and more preferably, three-quarters or more of the multiple normals V4121 may intersect the input / output terminal 12.

[0119] In addition, in this modification, all of the normals V4221 of the curved electrode fingers S4221 of the resonator S42 intersect with the input / output terminals 12 in a plan view of the substrate 10.

[0120] As described above, in this modified example, by changing the positional relationship between the resonators S41, S42, and S43 and the input / output terminal 12, it is possible to make all of the multiple normals V4121, V4221, and V4321 intersect with the input / output terminal 12 in all of the resonators S41, S42, and S43.

[0121] (Variation 2 of Embodiment 1) Next, Variation 2 of Embodiment 1 will be described. In this variation, the main difference from Variation 1 is the shape of the resonator S42. This variation will be described below with reference to FIG. 9 , focusing on the differences from Variation 1 of Embodiment 1.

[0122] 9 is a partial plan view of the acoustic wave filter 1 according to this modification. The portion of the acoustic wave filter 1 shown in FIG. 9 corresponds to the portion indicated by region vii in FIG.

[0123] 9 is an example of the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12, and the positional relationship between the resonators S41, S42, and S43 and the input / output terminals 12 is not limited to the positional relationship shown in FIG. 9. Therefore, the following description of the resonators S41, S42, and S43 and the input / output terminals 12 should not be interpreted in a restrictive manner.

[0124] In this modification, the resonator S42 includes an IDTS421 and a reflector S422, each having a plurality of non-curved electrode fingers arranged in the y direction. Even in this case, all of the plurality of normals V4221 of the non-curved electrode finger S4221A at one end of the plurality of non-curved electrode fingers in the y direction intersect with the input / output terminal 12.

[0125] As described above, in this modified example, even if the electrode fingers of resonator S42 are non-curved electrode fingers, all of the normals V4121, V4221, and V4321 can intersect with the input / output terminal 12 in all of resonators S41, S42, and S43.

[0126] (Third Modification of First Embodiment) Next, a third modification of the first embodiment will be described. This modification differs from the first embodiment mainly in that the ground terminal 13 is disposed between the resonators P31 and S22 and the resonators S42 and S43. This modification will be described below with reference to FIG. 10 , focusing on the differences from the first embodiment.

[0127] Fig. 10 is a partial plan view of an acoustic wave filter 1 according to this modification. Note that, in this modification, Fig. 10 illustrates an example of the positional relationship between the resonators P31, S22, S42, and S43 and the ground terminal 13, and the positional relationship between the resonators P31, S22, S42, and S43 and the ground terminal 13 is not limited to the positional relationship shown in Fig. 10. Therefore, the following description of the resonators P31, S22, S42, and S43 and the ground terminal 13 should not be interpreted in a restrictive manner.

[0128] The resonator S42 is an example of a first resonator and has a plurality of curved electrode fingers arranged in the y direction (first direction). Of the plurality of curved resonators of the resonator S42, all of the normals to the extension direction of the curved electrode fingers located near the ground terminal 13 and at one end in the y direction intersect with the ground terminal 13. However, only some of the normals may intersect with the ground terminal 13.

[0129] Resonator S43 is an example of a second resonator and has a plurality of curved electrode fingers aligned in the y direction. Of the plurality of curved resonators of resonator S43, all of the normals to the extension direction of the curved electrode fingers located near ground terminal 13 and at one end in the y direction intersect with ground terminal 13. Note that only some of the normals may intersect with ground terminal 13.

[0130] Resonator S22 is an example of a second resonator and has a plurality of curved electrode fingers aligned in the y direction. Of the plurality of curved resonators of resonator S22, all of the normals to the extension direction of the curved electrode fingers located near ground terminal 13 and at one end in the y direction intersect with ground terminal 13. However, only some of the normals may intersect with ground terminal 13.

[0131] The resonator P31 is arranged adjacent to the resonator S42 in the x direction (second direction). The resonator P31 has a plurality of curved electrode fingers arranged in the y direction. Of the plurality of curved resonators of the resonator P31, all of the normals to the extension direction of the curved electrode fingers located near the ground terminal 13 and at one end in the y direction intersect with the ground terminal 13. Note that only some of the normals may intersect with the ground terminal 13.

[0132] The ground terminal 13 is an example of a first external connection terminal and is disposed between the resonators S42 and S43, between the resonators S42 and S22, between the resonators P31 and S22, and between the resonators S31 and S43.

[0133] As described above, in the acoustic wave filter 1 according to this modification, the ground terminal 13 may be disposed between the resonator S42 and the resonator S22 and / or S43.

[0134] This allows acoustic waves leaking from the resonator S42 and the resonators S22 and / or S43 to be attenuated in the same area of ​​the ground terminal 13, which can contribute to miniaturization of the acoustic wave filter 1.

[0135] Second Embodiment Next, a second embodiment will be described. This embodiment differs from the first embodiment in that the normals to the tips of the curved electrode fingers intersect with the external connection terminals, rather than the normals to the curved electrode fingers at both ends in the arrangement direction of the plurality of curved electrode fingers. The following describes the second embodiment, focusing on the differences from the first embodiment, with reference to FIG. 12 .

[0136] 11 is a partial plan view of an acoustic wave filter 1 according to this preferred embodiment. As shown in FIG. 11 , in this preferred embodiment, a resonator P21 included in the resonator P2 and a resonator P31 included in the resonator P3 each have a plurality of curved electrode fingers aligned in the y direction (first direction).

[0137] The resonator P21 includes an IDTP211, a reflector P212, and a reflector not shown in Fig. 11. The IDTP211 is disposed in the y direction between the reflector P212 and the reflector not shown in Fig. 11. Some of multiple normals V211 to center lines extending in the extension direction at the tips of multiple curved electrode fingers of the IDTP211 intersect with the ground terminal 13.

[0138] The resonator P31 includes an IDTP311, a reflector P312, and a reflector not shown in Fig. 11. The IDTP311 is disposed in the y direction between the reflector P312 and the reflector not shown in Fig. 11. Normal lines V311 at the tips of some of the curved electrode fingers of the IDTP311 intersect with the ground terminal 13. Note that the normal line V311 at the tip of only one of the curved electrode fingers may intersect with the ground terminal 13.

[0139] As described above, the acoustic wave filter 1 according to this embodiment includes the substrate 10 including the piezoelectric layer 104, the resonator P21 arranged on the piezoelectric layer 104 and having a plurality of curved electrode fingers, and the ground terminal 13, and the normal V211 at the tip of at least one of the plurality of curved electrode fingers of the resonator P21 intersects with the ground terminal 13 in a planar view of the substrate 10.

[0140] According to this, since the normal V211 at the tip of at least one of the plurality of curved electrode fingers of the resonator P21 intersects with the ground terminal 13, the components of the elastic waves leaking from the tips of the plurality of curved electrode fingers to the outside of the resonator P21 can be effectively attenuated in the area of ​​the ground terminal 13, thereby suppressing unwanted responses.

[0141] While the acoustic wave filter according to one aspect of the present invention has been described above based on an embodiment, the acoustic wave filter according to the present invention is not limited to the above embodiment. The present invention also includes other embodiments realized by combining any of the components in the above embodiment, modifications obtained by applying various modifications to the above embodiment that would occur to those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the above resonator or the above acoustic wave filter.

[0142] For example, in the above embodiments, each resonator includes a pair of reflectors. However, this is not limiting. That is, each resonator may not include a reflector. For example, the resonator S22 may not include the reflectors S222 and S223, and the resonator P31 may not include the reflectors P312 and P313. FIG. 12 is a partial plan view of an acoustic wave filter 1 according to another embodiment. As shown in FIG. 12 , the resonator S22 includes an IDTS221 but does not include the reflectors S222 and S223. In this case, the curved electrode fingers S2221 and S2232 located at both ends of the curved electrode fingers in the y direction are included in the IDTS221. Similarly, the resonator P31 includes an IDTP311 but does not include the reflectors P312 and P313. In this case, the curved electrode fingers P3121 and P3132 located at both ends of the curved electrode fingers in the y direction are included in the IDTP311.

[0143] As described above, in the acoustic wave filter 1 according to another embodiment, the resonator S22 may include the IDTS 221 including the curved electrode fingers S2221 and S2232.

[0144] This makes it possible to suppress unwanted responses even in the resonator S22 that does not include a reflector.

[0145] In the above embodiments, the lengths of the curved electrode fingers included in one resonator are equal, but the lengths of the curved electrode fingers do not have to be equal. Also, each resonator may have a 2D piston structure or a 3D piston structure.

[0146] For example, the length of the curved electrode fingers may be shorter at both ends or one end of the resonator. In such a case, the curved electrode fingers at both ends or one end of the multiple curved electrode fingers in the y direction are shorter than the other curved electrode fingers, thereby reducing the effect on acoustic wave leakage. As a result, the curved electrode fingers at both ends or one end are no longer suitable as electrode fingers for determining the position of the ground terminal. Therefore, the curved electrode fingers used to determine the position of the ground terminal in such a case will be described with reference to FIGS. 13 and 14 .

[0147] Fig. 13 is a partial plan view of an acoustic wave filter 1 according to another embodiment. Fig. 14 is a plan view of a resonator S22 according to another embodiment. Note that in Fig. 13, the curved electrode fingers S2222 and P3122 are represented by dashed lines to improve visibility, but the curved electrode fingers S2222 and P3122 are actually formed continuously, not intermittently.

[0148] 13, in the resonator S22, the length of the curved electrode fingers decreases toward one end in the y direction. The curved electrode finger S2221 at one end in the y direction of the resonator S22 is the shortest among the curved electrode fingers of the resonator S22. Therefore, in FIG. 13, the curved electrode finger S2222, rather than the curved electrode finger S2221 at one end in the y direction of the multiple curved electrode fingers, is used to determine the position of the ground terminal 13a.

[0149] The curved electrode finger S2222 is an example of a first curved electrode finger and has a length in the y direction equal to the average length of the curved electrode fingers arranged in the central region of the resonator S22. The curved electrode finger S2222 is an end curved electrode finger in the y direction among two or more curved electrode fingers arranged in the central region and having the same average length.

[0150] The multiple normal lines V2222 are an example of multiple first normal lines, and are a collection of straight lines that are locally perpendicular to the center line of the curved electrode finger S2222. In a plan view of the substrate 10, at least one of the multiple normal lines V2222 intersects with the ground terminal 13a. In other words, the position of the ground terminal 13a is determined so as to intersect with at least one of the multiple normal lines V2222.

[0151] 13, similarly to the resonator S22, the length of the curved electrode fingers of the resonator P31 decreases toward one end in the y direction. Therefore, in FIG. 13, the curved electrode finger P3122, not the curved electrode finger P3121 at one end of the plurality of curved electrode fingers in the y direction, is used to determine the position of the ground terminal 13a.

[0152] The curved electrode finger P3122 is an example of a third curved electrode finger, and is a curved electrode finger having a length in the y direction equal to the average length of the curved electrode fingers arranged in the central region of the resonator P31. The curved electrode finger P3122 is a curved electrode finger at one end in the y direction among two or more curved electrode fingers having the same average length as the curved electrode fingers arranged in the central region.

[0153] The multiple normal lines V3122 are an example of multiple third normal lines, and are a collection of straight lines that are locally perpendicular to the center line of the curved electrode finger P3122. In a plan view of the substrate 10, at least one of the multiple normal lines V3122 intersects with the ground terminal 13a. In other words, the position of the ground terminal 13a is determined so as to intersect with at least one of the multiple normal lines V3122.

[0154] It should be noted that "a length equal to the average length" means not only a length strictly equal to the average length, but also a length within a range (within a range of ±10%) that can be considered substantially the same as a length strictly equal to the average length.

[0155] The "central region of a resonator" refers to one of the three regions obtained by dividing the resonator in the x direction into thirds so that the ratio of lengths in the y direction is 1:2:1, and refers to the region located between the two end regions in the y direction. For example, in the resonator S22 in Fig. 14, the central region is the 50% region located between the two 25% regions (end regions) in the y direction.

[0156] The "length of the curved electrode finger" refers to the length of the curve (center line) connecting the centers of the curved electrode fingers in the width direction. For example, in the curved electrode finger S2221 in FIG. 5, the length of the curved electrode finger S2221 is the length of the center line X2221.

[0157] As described above, when the length of the curved electrode fingers is short at both ends or one end of the resonator S22 / P31, the position of the ground terminal 13a is determined using curved electrode fingers having a length equal to the average length of the curved electrode fingers arranged in the central region of the resonator S22 / P31, thereby making it possible to suppress unwanted responses as in the above-mentioned embodiments.

[0158] If the distance between the busbar electrodes is different between the central region and the edge region, the length of the curved electrode fingers in the edge region may not be equal to the length of the curved electrode fingers in the central region. In such a case, the first curved electrode finger and the third curved electrode finger may be limited to curved electrode fingers whose lengths occupy 90% or more of the range between the busbar electrodes.

[0159] In each of the above embodiments, each resonator may be covered with a protective film for temperature compensation. In this case, the surface of the protective film for temperature compensation may be covered with a protective film for improving moisture resistance.

[0160] In the above embodiments and their modifications, it is desirable to arrange the external connection terminals at positions that intersect with the normals to the curved electrode fingers, but even if external connection terminals are not arranged, the damping effect of the sealing material arranged on the periphery of the chip can be expected. Therefore, it is desirable to arrange the resonators so that the concave side (the side where multiple normals intersect) of the curved electrode fingers is closer to the periphery of the chip than the convex side (the side where multiple normals extend).

[0161] In the above embodiments and their modifications, the external connection terminals arranged to intersect with the normals of the curved electrode fingers do not necessarily have to be terminals electrically connected to the outside. In addition to or instead of the external connection terminals, protruding structures may be arranged on the piezoelectric substrate, structures carved into the piezoelectric substrate, or acoustic wave scattering structures including multiple protruding structures may be arranged.

[0162] Here, a procedure for reading the shape of the electrode fingers from a resonator of an actual acoustic wave filter will be described with reference to Figures 15A, 15B, 15C, and 15D. Figures 15A to 15D are diagrams for explaining the procedure for reading the shape of the electrode fingers from a resonator. The shape of the electrode fingers is read in the following procedure.

[0163] (1) An image of the resonator is acquired using a scanning electron microscope (SEM). For example, an image of the resonator as shown in FIG. 15A is acquired. Note that the device for acquiring the image of the resonator is not limited to an SEM. For example, an optical microscope or a laser scanning microscope (LSM) may be used.

[0164] (2) The acquired image is processed so that the electrode finger edges can be distinguished. For example, the contrast of the image is adjusted as shown in FIG. 15B.

[0165] (3) Edge detection is performed on the processed image to extract the coordinate values ​​of the edges, for example, as shown in FIG. 15C.

[0166] (4) Since the actual electrode finger ends are not smooth, the extracted edges are interpolated with a curve approximated by a polynomial in an appropriate region size. For example, the edges are interpolated with a curve as shown in FIG. 15D.

[0167] (5) The center of gravity is determined from a pair of curves extending in the extension direction of the electrode fingers. The center of gravity is determined by a line connecting the midpoints of lines connecting any two corresponding points on the pair of curves.

[0168] (6) The normal direction at each coordinate point is calculated from the approximation formula of the curve, and the line width and pitch of the electrode fingers are calculated in the normal direction. The duty (metalized ratio) of the electrode fingers is calculated as line width / pitch.

[0169] (7) Calculate the radius (r) of a locally approximated perfect circle at any point on the curve, and calculate the reciprocal of the calculated r (1 / r) as the curvature, which represents the degree of curvature of the curve.

[0170] The characteristics of the acoustic wave filters described in accordance with the above embodiments will be described below.

[0171] <1> An acoustic wave filter comprising: a substrate including a piezoelectric layer; a first resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers aligned in a first direction; and a first external connection terminal, wherein the plurality of curved electrode fingers of the first resonator include first curved electrode fingers and second curved electrode fingers located at opposite ends in the first direction; the first external connection terminal is closer to the first curved electrode fingers than the second curved electrode fingers; and at least one of a plurality of first normals to an extension direction of the first curved electrode fingers intersects with the first external connection terminal in a plan view of the substrate.

[0172] <2> The acoustic wave filter according to <1>, wherein the first curved electrode finger is curved such that a central portion in an extension direction of the first curved electrode finger is away from the first external connection terminal in a plan view of the substrate.

[0173] <3> The acoustic wave filter according to <1> or <2>, wherein at least half of the plurality of first normals intersect with the first external connection terminal in a plan view of the substrate.

[0174] <4> The acoustic wave filter according to <3>, wherein three-quarters or more of the plurality of first normals intersect with the first external connection terminal in a plan view of the substrate.

[0175] <5> The acoustic wave filter according to <4>, wherein all of the plurality of first normal lines intersect with the first external connection terminal in a plan view of the substrate.

[0176] <6> The acoustic wave filter according to any one of <1> to <5>, further comprising a second external connection terminal that is closer to the second curved electrode fingers than the first curved electrode fingers, and at least one of a plurality of second normals to an extension direction of the second curved electrode fingers intersects with the second external connection terminal in a plan view of the substrate.

[0177] <7> The acoustic wave filter according to <6>, wherein the second curved electrode finger is curved such that a central portion in an extension direction of the second curved electrode finger approaches the second external connection terminal in a plan view of the substrate.

[0178] <8> The acoustic wave filter according to <6> or <7>, wherein at least half of the second normals intersect with the second external connection terminal in a plan view of the substrate.

[0179] <9> The acoustic wave filter according to <8>, wherein three-quarters or more of the second normals intersect with the second external connection terminal in a plan view of the substrate.

[0180] <10> The acoustic wave filter according to <9>, wherein all of the second normal lines intersect with the second external connection terminal in a plan view of the substrate.

[0181] <11> The acoustic wave filter according to any one of <1> to <10>, further comprising a second resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers aligned in the first direction, wherein the plurality of curved electrode fingers of the second resonator include third and fourth curved electrode fingers located at opposite ends in the first direction, wherein the first external connection terminal is closer to the third curved electrode finger than the fourth curved electrode finger, and wherein at least one of a plurality of third normals to an extension direction of the third curved electrode finger intersects with the first external connection terminal in a plan view of the substrate.

[0182] <12> The acoustic wave filter according to <11>, wherein the third curved electrode finger is curved such that a central portion in an extension direction of the third curved electrode finger is curved away from the first external connection terminal in a plan view of the substrate.

[0183] <13> The acoustic wave filter according to <11> or <12>, wherein at least half of the third normals intersect with the first external connection terminal in a plan view of the substrate.

[0184] <14> The acoustic wave filter according to <13>, wherein three-quarters or more of the third normals intersect with the first external connection terminal in a plan view of the substrate.

[0185] <15> The acoustic wave filter according to <14>, wherein all of the third normals intersect with the first external connection terminal in a plan view of the substrate.

[0186] <16> The acoustic wave filter according to any one of <11> to <15>, wherein the first resonator and the second resonator are arranged adjacent to each other in a second direction perpendicular to the first direction.

[0187] <17> The acoustic wave filter according to any one of <11> to <15>, wherein the first external connection terminal is disposed between the first resonator and the second resonator.

[0188] <18> The acoustic wave filter according to any one of <1> to <17>, wherein the first resonator includes: a first reflector having the first curved electrode fingers; a second reflector having the second curved electrode fingers; and an IDT (Interdigital Transducer) disposed between the first reflector and the second reflector.

[0189] <19> The acoustic wave filter according to any one of <1> to <17>, wherein the first resonator includes an IDT having the first curved electrode fingers and the second curved electrode fingers.

[0190] <20> An acoustic wave filter comprising: a substrate including a piezoelectric layer; a resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers; and an external connection terminal, wherein a normal to a center line extending in an extension direction at a tip end of at least one of the plurality of curved electrode fingers of the resonator intersects with the external connection terminal in a plan view of the substrate.

[0191] <21> An acoustic wave filter comprising: a substrate including a piezoelectric layer; a first resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers aligned in a first direction; and a first external connection terminal, wherein the plurality of curved electrode fingers of the first resonator include first and second curved electrode fingers having lengths equal to an average length of curved electrode fingers disposed in a central region of the first resonator in the first direction, the first and second curved electrode fingers being two curved electrode fingers at opposite ends in the first direction among two or more curved electrode fingers of the first resonator having lengths equal to the average length, the first external connection terminal being closer to the first curved electrode finger than the second curved electrode finger, and at least one of a plurality of first normals to an extension direction of the first curved electrode finger intersects the first external connection terminal in a plan view of the substrate.

[0192] The present invention can be widely used as an acoustic wave filter included in a front end portion of communication devices such as mobile phones.

[0193] REFERENCE SIGNS LIST 1 Acoustic wave filter 10 Substrate 11, 12 Input / output terminal 13, 13a, 13b Ground terminal 14 Pad electrode 15 Sealant 101 Support substrate 102 High acoustic velocity layer 103 Low acoustic velocity layer 104 Piezoelectric layer 131 Bump electrode 132 Via conductor P1, P2, P3, P4, S1, S2, S3, S4 Resonator P11, P12, P21, P31, P41, S11, S12, S13, S21, S22, S31, S32, S41, S42, S43 Resonator P211, P311, S221, S411, S421, S431 IDT P212, P312, P313, S222, S223, S412, S422, S423, S432, S433 Reflector P3121, P3122, P3132, S2221, S2222, S2232, S4121, S4221, S4232, S4321, S4332 Curved electrode finger S4221A Non-curved electrode finger V211, V311, V2221, V2222, V2232, V3121, V3122, V4121, V4221, V4321 Normal line X2221 Center line

Claims

1. An acoustic wave filter comprising: a substrate including a piezoelectric layer; a first resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers aligned in a first direction; and a first external connection terminal, wherein the plurality of curved electrode fingers of the first resonator include first curved electrode fingers and second curved electrode fingers located at both ends in the first direction; the first external connection terminal is closer to the first curved electrode fingers than the second curved electrode fingers; and at least one of a plurality of first normals to the extension direction of the first curved electrode fingers intersects with the first external connection terminal in a planar view of the substrate.

2. The acoustic wave filter according to claim 1, wherein the first curved electrode finger is curved such that a central portion in the extension direction of the first curved electrode finger is away from the first external connection terminal in a plan view of the substrate.

3. The acoustic wave filter according to claim 1, wherein at least half of the plurality of first normals intersect with the first external connection terminal in a plan view of the substrate.

4. The acoustic wave filter according to claim 3, wherein at least three-quarters of the plurality of first normals intersect with the first external connection terminal in a plan view of the substrate.

5. The acoustic wave filter according to claim 4, wherein all of the plurality of first normal lines intersect with the first external connection terminal in a plan view of the substrate.

6. The acoustic wave filter according to any one of claims 1 to 5, further comprising a second external connection terminal that is closer to the second curved electrode fingers than the first curved electrode fingers, and at least one of a plurality of second normals to the extension direction of the second curved electrode fingers intersects with the second external connection terminal in a plan view of the substrate.

7. The acoustic wave filter according to claim 6, wherein the second curved electrode finger is curved such that a center portion in an extension direction of the second curved electrode finger approaches the second external connection terminal in a plan view of the substrate.

8. The acoustic wave filter according to claim 6, wherein at least half of the plurality of second normals intersect with the second external connection terminal in a plan view of the substrate.

9. The acoustic wave filter according to claim 8, wherein at least three-quarters of the plurality of second normals intersect with the second external connection terminal in a plan view of the substrate.

10. The acoustic wave filter according to claim 9, wherein all of the plurality of second normal lines intersect with the second external connection terminal in a plan view of the substrate.

11. The acoustic wave filter according to any one of claims 1 to 10, further comprising a second resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers aligned in the first direction, the plurality of curved electrode fingers of the second resonator including third and fourth curved electrode fingers at opposite ends in the first direction, the first external connection terminal being closer to the third curved electrode finger than the fourth curved electrode finger, and at least one of a plurality of third normals to the extension direction of the third curved electrode finger intersecting the first external connection terminal in a plan view of the substrate.

12. The acoustic wave filter according to claim 11, wherein the third curved electrode finger is curved such that a central portion in the extension direction of the third curved electrode finger is away from the first external connection terminal in a plan view of the substrate.

13. The acoustic wave filter according to claim 11, wherein at least half of the plurality of third normals intersect with the first external connection terminal in a plan view of the substrate.

14. The acoustic wave filter according to claim 13, wherein at least three-quarters of the plurality of third normals intersect with the first external connection terminal in a plan view of the substrate.

15. The acoustic wave filter according to claim 14, wherein all of the third normals intersect with the first external connection terminal in a plan view of the substrate.

16. The acoustic wave filter according to claim 11, wherein the first resonator and the second resonator are arranged adjacent to each other in a second direction perpendicular to the first direction.

17. The acoustic wave filter according to any one of claims 11 to 15, wherein the first external connection terminal is disposed between the first resonator and the second resonator.

18. The acoustic wave filter according to any one of claims 1 to 17, wherein the first resonator includes: a first reflector having the first curved electrode fingers; a second reflector having the second curved electrode fingers; and an IDT (Interdigital Transducer) disposed between the first reflector and the second reflector.

19. An acoustic wave filter comprising: a substrate including a piezoelectric layer; a resonator disposed on the piezoelectric layer and having a plurality of curved electrode fingers; and an external connection terminal, wherein a normal to a center line extending in an extension direction at a tip of at least one of the plurality of curved electrode fingers of the resonator intersects with the external connection terminal in a plan view of the substrate.

20. An acoustic wave filter comprising: a substrate including a piezoelectric layer; a first resonator arranged on the piezoelectric layer and having a plurality of curved electrode fingers aligned in a first direction; and a first external connection terminal, wherein the plurality of curved electrode fingers of the first resonator include first and second curved electrode fingers having lengths equal to an average length in the first direction of curved electrode fingers arranged in a central region of the first resonator, the first and second curved electrode fingers being two curved electrode fingers at opposite ends in the first direction among two or more curved electrode fingers of the first resonator having lengths equal to the average length, the first external connection terminal being closer to the first curved electrode finger than the second curved electrode finger, and at least one of a plurality of first normals to the extension direction of the first curved electrode finger intersects the first external connection terminal in a plan view of the substrate.

Images