Surface acoustic wave resonator, surface acoustic wave filter, and multiplexer

Abstract

This surface acoustic wave resonator (1) comprises: at least one electrode (4) disposed on a substrate (3) and including an IDT electrode (41); and a plurality of load members (51) that are disposed on or in the substrate (3), are spaced apart from each other, and are composed of a dielectric material. Each of the plurality of load members (51) at least partially overlaps at least one corresponding electrode finger in a planar view of the substrate (3). The number of electrode fingers that overlap the plurality of load members (51) among the electrode fingers disposed in a first sub-region (3b1) and the number of electrode fingers that overlap the plurality of load members (51) among the electrode fingers disposed in a third sub-region (3b3) are each greater than the number of electrode fingers that overlap the plurality of load members (51) among the electrode fingers disposed in a second sub-region (3b2). The plurality of load members (51) include two or more load members (51) that overlap the electrode fingers disposed in the first sub-region (3b1) and two or more load members (51) that overlap the electrode fingers disposed in the third sub-region (3b3).

Description

Surface acoustic wave resonator, surface acoustic wave filter and multiplexer

[0001] The present invention relates to a surface acoustic wave resonator, a surface acoustic wave filter, and a multiplexer.

[0002] Patent Document 1 discloses a surface acoustic wave filter that can improve the Q value (Quality Factor), which is an index representing the sharpness of the resonance peak, by using a substrate formed of a laminate of a high acoustic velocity support substrate, a low acoustic velocity layer, and a piezoelectric layer.

[0003] International Publication No. 2012 / 086639

[0004] However, further improvement in the Q value of conventional surface acoustic wave filters is desired.

[0005] Therefore, the present invention provides a surface acoustic wave resonator, a surface acoustic wave filter, or a multiplexer that can improve the Q value.

[0006] A surface acoustic wave resonator according to one aspect of the present invention includes a substrate including a piezoelectric layer, at least one electrode including an IDT electrode disposed on the substrate, and a plurality of first load members made of a dielectric material disposed spaced apart from one another on or within the substrate, wherein the at least one electrode includes a plurality of electrode fingers aligned along a first axis on the substrate, the plurality of electrode fingers extending along a second axis perpendicular to the first axis, each of the plurality of first load members at least partially overlapping at least one corresponding electrode finger in a plan view of the substrate, and a plurality of electrode fingers among the electrode fingers disposed in the first sub-region that overlap with the plurality of first load members. the number of electrode fingers arranged in the third sub-region that overlap with the plurality of first load members and the number of electrode fingers arranged in the third sub-region that overlap with the plurality of first load members are each greater than the number of electrode fingers arranged in the second sub-region that overlap with the plurality of first load members, the first sub-region, the second sub-region, and the third sub-region are obtained by equally dividing an area on the substrate in which the plurality of electrode fingers are arranged in the direction of the second axis, the second sub-region is located between the first sub-region and the third sub-region, and the plurality of first load members include two or more first load members that overlap with the electrode fingers arranged in the first sub-region and two or more first load members that overlap with the electrode fingers arranged in the third sub-region.

[0007] A surface acoustic wave filter according to one aspect of the present invention includes at least one series arm resonator and at least one parallel arm resonator, and at least one of the at least one series arm resonator and the at least one parallel arm resonator is the above-described surface acoustic wave resonator.

[0008] A multiplexer according to one aspect of the present invention comprises a transmit filter connected between an antenna connection terminal and a PA connection terminal and having a pass band including a predetermined band of transmit band, and a receive filter connected between the antenna connection terminal and an LNA connection terminal and having a pass band including a predetermined band of receive band, wherein at least one of the transmit filter and the receive filter is a surface acoustic wave filter as described above.

[0009] A surface acoustic wave resonator according to one aspect of the present invention comprises a substrate including a piezoelectric layer, at least one electrode arranged on the substrate and including an IDT electrode, and a dielectric film arranged on the at least one electrode, wherein the at least one electrode includes a plurality of electrode fingers arranged along a first axis on the substrate, the plurality of electrode fingers each extending along a second axis perpendicular to the first axis, wherein the average thickness of the dielectric film on the electrode fingers arranged in the first sub-region and the average thickness of the dielectric film on the electrode fingers arranged in the third sub-region are each greater than the average thickness of the dielectric film on the electrode fingers arranged in the second sub-region, and the first sub-region, the second sub-region, and the third sub-region are obtained by equally dividing an area on the substrate in which the plurality of electrode fingers are arranged in the direction of the second axis, and the second sub-region is located between the first sub-region and the third sub-region.

[0010] According to the present invention, it is possible to provide a surface acoustic wave resonator, a surface acoustic wave filter, or a multiplexer that can improve the Q value.

[0011] FIG. 1 is a plan view of a surface acoustic wave resonator according to a first embodiment. FIG. 2 is a cross-sectional view of the surface acoustic wave resonator according to the first embodiment. FIG. 3 is a partial cross-sectional view of the surface acoustic wave resonator according to the first embodiment. FIG. 4 is a partial cross-sectional view of the surface acoustic wave resonator according to the first embodiment. FIG. 5 is a plan view of a plurality of electrodes and a plurality of load members according to the first embodiment. FIG. 6 is a graph showing frequency characteristics of the Q value of surface acoustic wave resonators according to a first example and a first comparative example. FIG. 7 is a graph showing resonance characteristics of surface acoustic wave resonators according to the first example and a second comparative example. FIG. 8 is a graph showing resonance characteristics of surface acoustic wave resonators according to the first example and a third comparative example. FIG. 9 is a graph showing frequency characteristics of the Q value of surface acoustic wave resonators according to the second example and a fourth comparative example. FIG. 10 is a cross-sectional view of a surface acoustic wave resonator according to a first modified example of the first embodiment. FIG. 11 is a plan view of a plurality of electrodes and a plurality of load members according to a second modified example of the first embodiment. FIG. 12 is a plan view of a plurality of electrodes and a plurality of load members according to a third modified example of the first embodiment. FIG. 13 is a plan view of a plurality of electrodes and a plurality of load members according to a fourth modified example of the first embodiment. Fig. 14 is a partial cross-sectional view of a surface acoustic wave resonator according to a fourth modification of the first embodiment. Fig. 15 is a plan view of a surface acoustic wave resonator according to a fifth modification of the first embodiment. Fig. 16 is a cross-sectional view of a surface acoustic wave resonator according to the fifth modification of the first embodiment. Fig. 17 is a circuit configuration diagram of a surface acoustic wave filter according to a second embodiment. Fig. 18 is a plan view of a surface acoustic wave filter according to the second embodiment. Fig. 19 is a circuit configuration diagram of a multiplexer according to a third embodiment.

[0012] 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.

[0013] 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.

[0014] In the following figures, 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. Specifically, the x-axis is the axis along which multiple electrode fingers arranged on the substrate are aligned, and is sometimes expressed as the propagation direction of surface acoustic waves. The y-axis is the axis along which each of the multiple electrode fingers arranged on the substrate extends. 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.

[0015] In this disclosure, "connected" includes not only direct connection by a connection terminal and / or a wiring conductor, but also electrical connection via another circuit element. "Directly connected" means direct connection by a connection terminal and / or a wiring conductor without via another circuit element. "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.

[0016] "Terminal" means a point where a conductor within an element terminates. Note that terminal can be interpreted as any point on the conductor between elements or the entire conductor, not just a single point, if the impedance of the conductor between elements is sufficiently low.

[0017] The "passband of a filter" is defined as the portion of the frequency spectrum transmitted by the filter over which the output power is not attenuated by more than 3 dB below the maximum output power. The upper and lower ends of the passband of a bandpass filter are therefore identified as the higher and lower frequencies of the two points at which the output power is attenuated by 3 dB below the maximum output power.

[0018] The term "reception band" refers to a frequency band used for reception in a communication device, and the term "transmission band" refers to a frequency band used for transmission in a communication device. For example, in a band for frequency division duplex (FDD), different frequency bands (uplink band and downlink band) are used as the transmission band and the reception band. For example, in a band for time division duplex (TDD), the same frequency band is used as the transmission band and the reception band.

[0019] "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.

[0020] Furthermore, terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," 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.

[0021] (Embodiment 1) [1.1 Configuration of Surface Acoustic Wave Resonator 1] First, the overall configuration of a surface acoustic wave resonator 1 according to embodiment 1 will be specifically described with reference to Figures 1 and 2. Figures 1 and 2 are a plan view and a cross-sectional view of the surface acoustic wave resonator 1 according to this embodiment. The cross section of the surface acoustic wave resonator 1 in Figure 2 is taken along line ii-ii in Figure 1.

[0022] 1 and 2 are intended to explain a typical configuration of the surface acoustic wave resonator 1, and the configuration of the surface acoustic wave resonator 1 is not limited to the configuration shown in Fig. 1 and 2. Therefore, the following description of the surface acoustic wave resonator 1 should not be interpreted in a limiting manner.

[0023] The surface acoustic wave resonator 1 includes a substrate 3, a plurality of electrodes 4, and a dielectric film 5. The substrate 3 includes a piezoelectric layer 31, a low acoustic velocity layer 32, a high acoustic velocity layer 33, and a support substrate .

[0024] The piezoelectric layer 31 is a layer having piezoelectricity stacked on the low acoustic velocity layer 32, and is capable of propagating a surface acoustic wave (SAW). A plurality of electrodes 4 are disposed on the piezoelectric layer 31. The piezoelectric layer 31 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. The electrodes 4 may be disposed on one of the opposing principal surfaces 31 a and 31 b of the piezoelectric layer 31, or on the other principal surface 31 b.

[0025] The low acoustic velocity layer 32 is laminated on the high acoustic velocity layer 33 and is disposed between the piezoelectric layer 31 and the high acoustic velocity layer 33. The acoustic velocity of bulk waves propagating through the low acoustic velocity layer 32 is slower than the acoustic velocity of elastic waves, such as surface waves and boundary waves, propagating through the piezoelectric layer 31. The low acoustic velocity layer 32 may be made of a material such as silicon dioxide, glass, silicon oxynitride, lithium oxide, tantalum oxide, or a dielectric material such as 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 32 is not limited to these.

[0026] The high acoustic velocity layer 33 is stacked on the support substrate 34 and disposed between the low acoustic velocity layer 32 and the support substrate 34. The high acoustic velocity layer 33 confines the surface acoustic waves generated by the multiple electrodes 4 within the area where the piezoelectric layer 31 and the low acoustic velocity layer 32 are stacked, preventing the surface acoustic waves from leaking below the high acoustic velocity layer 33. The acoustic velocity of bulk waves propagating through the high acoustic velocity layer 33 is faster than the acoustic velocity of surface waves and boundary waves propagating through the piezoelectric layer 31. Examples of materials that can be used for the high acoustic velocity layer 33 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; dielectric materials 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 33 is not limited to these.

[0027] The support substrate 34 can support the piezoelectric layer 31, the low acoustic velocity layer 32, and the high acoustic velocity layer 33. Examples of materials that can be used for the support substrate 34 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; dielectrics 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 34 is not limited to these.

[0028] The high acoustic velocity layer 33 and the support substrate 34 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; 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; semiconductors such as silicon; and any combinations of these. 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.

[0029] The plurality of electrodes 4 are an example of at least one first electrode, and are disposed on the substrate 3 , and include an IDT (Interdigital Transducer) electrode 41 and a pair of reflective electrodes 42 .

[0030] The IDT electrode 41 is an example of a first IDT electrode, and includes two interdigitated comb electrodes arranged on the piezoelectric layer 31. The IDT electrode 41 can convert an electrical signal into a surface acoustic wave and vice versa. The IDT electrode 41 includes a plurality of electrode fingers 411 a and 411 b and busbar electrodes 412 a and 412 b.

[0031] The electrode fingers 411a and 411b are an example of a plurality of first electrode fingers, and are arranged alternately along the x-axis (first axis) and extend along the y-axis (second axis). One ends of the electrode fingers 411a are connected to the bus bar electrode 412a and extend from the bus bar electrode 412a in the negative direction of the y-axis. One ends of the electrode fingers 411b are connected to the bus bar electrode 412b and extend from the bus bar electrode 412b in the positive direction of the y-axis. Note that the electrode fingers 411a and 411b do not have to be arranged alternately one by one, and may be arranged alternately in groups of two or more, for example.

[0032] The busbar electrode 412a extends along the x-axis and is connected to one end of each of the electrode fingers 411a. The busbar electrode 412a is arranged parallel to the busbar electrode 412b and spaced apart from the busbar electrode 412b in the positive direction of the y-axis.

[0033] The busbar electrode 412b extends along the x-axis and is connected to one end of each of the electrode fingers 411b. The busbar electrode 412b is arranged parallel to the busbar electrode 412a and spaced apart from the busbar electrode 412a in the negative direction of the y-axis.

[0034] The pair of reflective electrodes 42 are an example of a pair of first reflective electrodes, and are arranged to sandwich the IDT electrode 41 in the x-axis direction in order to confine within the IDT electrode 41 a predetermined high-frequency signal that resonates in the IDT electrode 41. That is, the IDT electrode 41 is arranged between the pair of reflective electrodes 42 in the x-axis direction. Each of the pair of reflective electrodes 42 includes a plurality of electrode fingers 421 and busbar electrodes 422a and 422b. The plurality of electrode fingers 421 are an example of a plurality of first electrode fingers, and are aligned along the x-axis and extend along the y-axis, respectively. Both ends of the plurality of electrode fingers 421 are connected to the busbar electrodes 422a and 422b. The busbar electrode 422a extends along the x-axis and is connected to one end of the plurality of electrode fingers 421. The busbar electrode 422b extends along the x-axis, is arranged parallel to and opposite the busbar electrode 422a, and is connected to the other end of the plurality of electrode fingers 421.

[0035] The IDT electrode 41 and the pair of reflective electrodes 42 may be made of, for example, aluminum, titanium, gold, silver, copper, platinum, tungsten, molybdenum, ruthenium, or any combination thereof. Note that the materials for the IDT electrode 41 and the pair of reflective electrodes 42 are not limited to these. Furthermore, the materials for the IDT electrode 41 and the pair of reflective electrodes 42 may be different from each other or the same.

[0036] The dielectric film 5 is disposed on the substrate 3 and covers the substrate 3 and the plurality of electrodes 4. The dielectric film 5 includes a plurality of load members 51 and a protective film 52.

[0037] The multiple load members 51 are an example of multiple first load members and are made of a dielectric. In this embodiment, the multiple load members 51 are multiple load films (an example of multiple first load films) arranged apart from each other on the substrate 3. Each of the multiple load members 51 at least partially overlaps with at least one corresponding electrode finger in a plan view of the substrate 3. This allows the multiple load members 51 to add mass to some of the multiple electrode fingers 411 a, 411 b, and 421.

[0038] The load members 51 are made of a dielectric material, specifically, tantalum pentoxide (Ta ２ O５ ), niobium pentoxide (Nb ２ O ５ ), tungsten(VI) oxide (WO ３ ), silicon nitride (SiN), titanium oxide (IV) (TiO ２ ), cerium (IV) oxide (CeO ２ ), hafnium (IV) oxide (HfO ２ ), ytterbium(III) oxide (Yb ２ O ３ ), silicon dioxide, alumina, or any combination thereof can be used, but is not limited to these. By using a dielectric material having a higher density than the protective film 52 as the material for the multiple load members 51, the multiple load members 51 can be made thinner. Note that the multiple load members 51 may be made of different materials.

[0039] The protective film 52 is disposed on the substrate 3 and covers the IDT electrode 41, the reflective electrode 42, and the main surface 3 a of the substrate 3. The material of the protective film 52 is a dielectric material, and specifically, it may be, but is not limited to, silicon dioxide, silicon nitride, alumina, or any combination thereof. The material of the protective film 52 may be different from the material of the load member 51 or may be the same as the material of the load member 51. The protective film 52 does not have to be included in the dielectric film 5, and may be removed from the surface acoustic wave resonator 1.

[0040] The electrode finger region 3b on the main surface 3a of the substrate 3 is a region in which a plurality of electrode fingers 411a, 411b, and 421 are arranged, and is equally divided into a first subregion 3b1, a second subregion 3b2, and a third subregion 3b3 in the y-axis direction. The electrode finger region 3b is defined as a rectangular region that surrounds the plurality of electrode fingers 411a, 411b, and 421 with the smallest area. In FIG. 1 , the first subregion 3b1, the second subregion 3b2, and the third subregion 3b3 are the left, center, and right partial regions of the electrode finger region 3b, respectively. The second subregion 3b2 is located between the first subregion 3b1 and the third subregion 3b3.

[0041] 1 and 2. For example, the surface acoustic wave resonator 1 may be a longitudinally coupled surface acoustic wave resonator. Furthermore, the substrate 3 of the surface acoustic wave resonator 1 does not need to include the low acoustic velocity layer 32 and the high acoustic velocity layer 33.

[0042] 3 and 4, the cross-sectional structures of the electrode finger 411a and the dielectric film 5 will be described. Note that the electrode finger 411a will be described below, but the other electrode fingers 411b and 421 are similar to the electrode finger 411a, and therefore their description will be omitted.

[0043] 3 and 4 are partial cross-sectional views of the surface acoustic wave resonator 1 according to this embodiment. Specifically, Fig. 3 is an enlarged view of part iii in Fig. 2, and Fig. 4 is an enlarged view of part iv in Fig. 2.

[0044] 3 and 4 are intended to illustrate typical configurations of the electrode fingers 411 a and the dielectric film 5, and the configurations of the electrode fingers 411 a and the dielectric film 5 are not limited to those illustrated in Fig. 3 and 4. Therefore, the following description of the electrode fingers 411 a and the dielectric film 5 should not be construed as limiting.

[0045] 3 , the electrode finger 411a is covered with a load member 51 and a protective film 52. Specifically, a part (right part) of the electrode finger 411a is covered with the load member 51 and the protective film 52, and the other part (left part) of the electrode finger 411a is not covered with the load member 51 but is covered with the protective film 52. The load member 51 is laminated on a part of the electrode finger 411a and the piezoelectric layer 31, and the protective film 52 is laminated on the other part of the electrode finger 411a, the piezoelectric layer 31, and the load member 51. Note that the load member 51 may be laminated on the protective film 52.

[0046] A midpoint c51 of the length of the load member 51 along the x-axis (width w51 of the load member 51) is shifted by a shift amount s51 in the positive direction of the x-axis of the IDT electrode 41 with respect to a midpoint c411 of the length of the electrode finger 411a along the x-axis (width w411 of the electrode finger 411a). In other words, the load member 51 is shifted toward the center of the IDT electrode 41 along the x-axis with respect to the corresponding electrode finger 411a.

[0047] Furthermore, the thickness t51a of the load member 51 on the top surface of the electrode finger 411a is larger than the thickness t51b of the load member 51 on the side surface of the electrode finger 411a and is larger than the thickness t52 of the protective film 52. Note that, hereinafter, when simply referring to the thickness of the load member on the electrode finger, this refers to the thickness of the load member on the top surface of the electrode finger (thickness t51a in FIG. 3).

[0048] 4, the electrode finger 411a is not covered by the load member 51 but is covered by the protective film 52. Therefore, the thickness t5 (=t52) of the dielectric film 5 on the electrode finger 411a in FIG. 4 is smaller than the thickness t5 (=t51a+t52) of the dielectric film 5 on the electrode finger 411a in FIG.

[0049] The thicknesses of the dielectric film 5, the load member 51 (load film), and the protective film 52 are measured by observing a cut surface of the surface acoustic wave resonator 1 with a scanning electron microscope (SEM). Here, the cut surface of the surface acoustic wave resonator 1 is a cut surface perpendicular to the main surface 3 a of the substrate 3 and passing through a straight line connecting the center points of the overlapping widths of the plurality of electrode fingers 411 a, 411 b, and 421. The overlapping widths of the plurality of electrode fingers 411 a, 411 b, and 421 are the lengths in the direction perpendicular to the propagation direction (y-axis direction) of the surface acoustic waves, of the regions where adjacent electrode fingers intersect, when viewed in the propagation direction (x-axis direction).

[0050] [1.3 Positions of the Electrode Fingers 411a, 411b, and 421 and the Load Members 51] Next, the positional relationship between the electrode fingers 411a, 411b, and 421 and the load members 51 in a plan view of the substrate 3 will be described with reference to FIG.

[0051] Fig. 5 is a plan view of the electrodes 4 and the load members 51 according to this embodiment. Specifically, Fig. 5 is a view of the electrodes 4 and the load members 51 orthogonally projected onto the xy plane.

[0052] 5 is intended to illustrate a typical positional relationship between the electrodes 4 and the load members 51, and the positional relationship between the electrodes 4 and the load members 51 is not limited to the positional relationship shown in FIG. 5. Therefore, the following description of the electrodes 4 and the load members 51 should not be construed as being limiting.

[0053] The multiple load members 51 correspond one-to-one to some of the multiple electrode fingers 411a, 411b, and 421. Each of the multiple load members 51 has a shape (rectangular) similar to that of the corresponding electrode finger 411a, 411b, or 421 and extends along the y-axis. Each of the multiple load members 51 partially overlaps with the corresponding electrode finger 411a, 411b, or 421 in a plan view of the substrate 3. Specifically, a portion of each of the multiple load members 51 overlaps with a portion of the corresponding electrode finger 411a, 411b, or 421, and the other portion of each of the multiple load members 51 overlaps with a portion of the gap between the corresponding electrode finger 411a, 411b, or 421 and the adjacent electrode finger 411a, 411b, or 421. In addition, each of the multiple load members 51 may overlap entirely, rather than partially, with a corresponding one of the electrode fingers 411 a, 411 b, or 421 in a plan view of the substrate 3. In Fig. 5, in a plan view of the substrate 3, the area of ​​the portion where each of the multiple load members 51 overlaps with a corresponding one of the electrode fingers 411 a, 411 b, or 421 is approximately half the total area of ​​each of the multiple load members 51, but is not limited to this.

[0054] Each of the multiple load members 51 is offset along the x-axis toward the center of the IDT electrode 41 with respect to a corresponding one of the electrode fingers 411a, 411b, or 421. For example, as shown in Fig. 3 , a midpoint c51 of the length of the load member 51 along the x-axis (width w51 of the load member 51) is offset along the x-axis toward the center of the IDT electrode 41 (positive direction of the x-axis) with respect to a midpoint c411 of the length of the electrode finger 411a along the x-axis (width w411 of the electrode finger 411a).

[0055] In a plan view of the substrate 3, the multiple load members 51 partially overlap with some of the multiple electrode fingers 411 a and 411 b of the IDT electrode 41, and partially overlap with some of the multiple electrode fingers 421 of each of the pair of reflecting electrodes 42. Specifically, the multiple load members 51 partially overlap with two of the multiple electrode fingers 411 a and 411 b of the IDT electrode 41 that are closer to the pair of reflecting electrodes 42. Furthermore, the multiple load members 51 partially overlap with two of the multiple electrode fingers 421 of each of the pair of reflecting electrodes 42 that are closer to the IDT electrode 41.

[0056] Of the electrode fingers 411a, 411b, and 421 arranged in the first sub-region 3b1, the number (four in FIG. 5 ) of electrode fingers that overlap with the load members 51 is greater than the number (zero in FIG. 5 ) of the electrode fingers 411a and 411b arranged in the second sub-region 3b2 that overlap with the load members 51. Similarly, of the electrode fingers 411a, 411b, and 421 arranged in the third sub-region 3b3, the number (four in FIG. 5 ) of electrode fingers that overlap with the load members 51 is greater than the number (zero in FIG. 5 ) of the electrode fingers 411a and 411b arranged in the second sub-region 3b2 that overlap with the load members 51.

[0057] Furthermore, the ratio (4 / 7 in Figure 5) of the number of electrode fingers overlapping with multiple load members 51 to the total number (7 in Figure 5) of electrode fingers 411a, 411b, and 421 arranged in the first sub-region 3b1 is greater than the ratio (0 / 7 in Figure 5) of the number of electrode fingers overlapping with multiple load members 51 to the total number (7 in Figure 5) of electrode fingers 411a and 411b arranged in the second sub-region 3b2. Similarly, the ratio (4 / 7 in Figure 5) of the number of electrode fingers overlapping with multiple load members 51 to the total number (7 in Figure 5) of electrode fingers 411a, 411b and 421 arranged in the third sub-region 3b3 is greater than the ratio (0 / 7 in Figure 5) of the number of electrode fingers overlapping with multiple load members 51 to the total number (7 in Figure 5) of electrode fingers 411a and 411b arranged in the second sub-region 3b2.

[0058] In this case, an electrode finger arranged across two sub-regions is counted in each of the two sub-regions as an electrode finger arranged in that sub-region. For example, in Fig. 5, the electrode finger 411a arranged at the boundary between the first sub-region 3b1 and the second sub-region 3b2 is counted as an electrode finger arranged in the first sub-region 3b1 and also as an electrode finger arranged in the second sub-region 3b2.

[0059] The number and arrangement of the electrode fingers overlapping the multiple load members 51 are not limited to those shown in Fig. 5 . For example, the multiple load members 51 may overlap the electrode fingers 411a and / or 411b arranged in the second sub-region 3b2. Furthermore, the multiple load members 51 may overlap all of the multiple electrode fingers 421 of the pair of reflecting electrodes 42. Furthermore, the multiple load members 51 may partially overlap one or more of the multiple electrode fingers 421 of each of the pair of reflecting electrodes 42 that are farther from the IDT electrode 41.

[0060] The plurality of electrode fingers 411a, 411b, and 421 arranged in each of the first sub-region 3b1 and the third sub-region 3b3 overlap with two or more load members 51, rather than with a single load member 51. In Fig. 5, the four electrode fingers 411a, 411b, and 421 arranged in each of the first sub-region 3b1 and the third sub-region 3b3 overlap with four load members 51. That is, the plurality of load members 51 includes two or more load members 51 overlapping with two or more electrode fingers arranged in the first sub-region 3b1 and two or more load members 51 overlapping with two or more electrode fingers arranged in the third sub-region 3b3.

[0061] The number, shape, and size (length along the x-axis, length along the y-axis, and thickness) of the plurality of load members 51 can be determined in accordance with the required specifications of the surface acoustic wave resonator 1. The number, shape, size, pitch, and duty ratio of the plurality of electrode fingers 411 a, 411 b, and 421 can also be determined in accordance with the required specifications of the surface acoustic wave resonator 1.

[0062] For example, the duty ratios of the electrode fingers 411a, 411b, and 421 do not have to be uniform within the surface acoustic wave resonator 1. For example, the duty ratio (w1 / p1) of the electrode fingers 411a, 411b, and 421 that overlap with the load members 51 may be different from the duty ratio (w2 / p2) of the electrode fingers 411a and 411b that do not overlap with the load members 51. The duty ratio of the electrode fingers is defined as the ratio of the average length (average width) of the electrode fingers along the x-axis to the average pitch of the electrode fingers.

[0063] Furthermore, for example, the pitches of the multiple electrode fingers 411 a, 411 b, and 421 do not need to be uniform within the surface acoustic wave resonator 1. For example, the pitch p3 between an electrode finger overlapping the load member 51 and an electrode finger not overlapping the load member 51 may be different from the pitch p1 of the multiple electrode fingers overlapping the load member 51, or may be different from the pitch p2 of the multiple electrode fingers not overlapping the load member 51. In other words, the interval (pitch p3) between an electrode finger overlapping one of the multiple load members 51 and an electrode finger adjacent to that electrode finger but not overlapping any of the multiple load members 51 may be different from the interval (pitch p1) between two adjacent electrode fingers overlapping the multiple load members 51, or may be different from the interval (pitch p2) between two adjacent electrode fingers not overlapping any of the multiple load members 51. The distance between two electrode fingers is defined as the length of a line segment on a line parallel to the x-axis that connects the midpoint of the length of one of the two electrode fingers along the x-axis to the midpoint of the length of the other of the two electrode fingers along the x-axis.

[0064] Furthermore, for example, the duty ratios of the electrode fingers 411a and 411b that do not overlap with the load members 51 may not be uniform within the surface acoustic wave resonator 1. For example, the width w2 of at least one of the electrode fingers 411a and 411b that do not overlap with the load members 51 may be different from the width w2 of at least another of the electrode fingers 411a and 411b that do not overlap with the load members 51. For example, the spacing (pitch p2) between adjacent electrode fingers of at least one set of the electrode fingers 411a and 411b that do not overlap with the load members 51 may be different from the spacing (pitch p2) between adjacent electrode fingers of at least another set of the electrode fingers 411a and 411b that do not overlap with the load members 51. Furthermore, the spacing (pitch p2) between adjacent electrode fingers of multiple sets of the electrode fingers 411a and 411b that do not overlap with the load members 51 may be different from each other. In this case, the intervals (pitch p2) between adjacent electrode fingers of all sets of the plurality of electrode fingers 411a and 411b that do not overlap with the plurality of load members 51 may be different from each other.

[0065] [1.4 Comparison of Characteristics of Surface Acoustic Wave Resonators Between Examples 1 and 2 and Comparative Examples 1 to 4] A comparison of the characteristics of the surface acoustic wave resonators according to Examples 1 and 2 based on the first embodiment and the surface acoustic wave resonators according to Comparative Examples 1 to 4 will be described with reference to FIGS. 6 to 9 .

[0066] The surface acoustic wave resonator according to Example 1 has the following specifications (a) to (h): (a) The support substrate 34 is a silicon substrate with a plane orientation

[111] . (b) The high acoustic velocity layer 33 is a silicon nitride (SiN) layer having a thickness of 300 nm. (c) The low acoustic velocity layer 32 is a silicon dioxide (SiO ) layer having a thickness of 673 nm. ２ (d) The piezoelectric layer 31 is a lithium tantalate (LiTaO) layer having a thickness of 1000 nm. ３) layer, the cut angle of which is 35 degrees. (e) The IDT electrode 41 has a three-layer structure consisting of a titanium (Ti) layer with a thickness of 60 nm, a copper-aluminum alloy (Al-1% Cu) layer with a thickness of 380 nm, and a titanium (Ti) layer with a thickness of 4 nm. The pitch of the IDT electrode 41 is 2.5 μm, and the duty ratio of the IDT electrode 41 is 0.435. The number of the plurality of electrode fingers 411 a and 411 b of the IDT electrode 41 is 81 each. (f) The number of the plurality of electrode fingers 421 of each of the pair of reflecting electrodes 42 is 10. (g) The load member 51 is a tantalum pentoxide (Ta) layer with a thickness of 120 nm. ２ O ５ The load member 51 covers the plurality of electrode fingers 421 of each of the pair of reflecting electrodes 42, and also covers five of the plurality of electrode fingers 411a and 411b of the IDT electrode 41 that are closest to each of the pair of reflecting electrodes 42. (h) The protective film 52 is a silicon dioxide (SiO ２ ) membrane.

[0067] The specifications of the surface acoustic wave resonator according to Example 2 are the same as those of the surface acoustic wave resonator according to Example 1 in (a) to (e) and (h), except that (f) and (g) are replaced with (f') and (g'). (f') The pair of reflecting electrodes 42 is not included. (g') The load member 51 is made of tantalum pentoxide (Ta) having a thickness of 120 nm. ２ O ５ The load member 51 covers ten electrode fingers 411 a and 411 b of the IDT electrode 41 that are closest to both ends in the propagation direction (x-axis direction).

[0068] 6 is a graph showing frequency characteristics of the Q value of the surface acoustic wave resonators according to Example 1 and Comparative Example 1. In FIG. 6, the horizontal axis represents frequency, and the vertical axis represents the Q value.

[0069] The surface acoustic wave resonator according to Comparative Example 1 is obtained by removing the load member 51 from the surface acoustic wave resonator according to Example 1. In other words, the dielectric film 5 of the surface acoustic wave resonator according to Comparative Example 1 includes only the protective film 52 and does not include the load member 51.

[0070] 6, the Q value of the surface acoustic wave resonator according to Example 1 is higher than the Q value of the surface acoustic wave resonator according to Comparative Example 1. In particular, the Q value is improved in the frequency range of 700 to 800 MHz.

[0071] 7 is a graph showing the resonance characteristics of the surface acoustic wave resonators according to Example 1 and Comparative Example 2. In FIG. 7, the horizontal axis represents frequency, and the vertical axis represents phase.

[0072] The surface acoustic wave resonator according to Comparative Example 2 is obtained by setting the amount of misalignment (misalignment amount s51 in FIG. 3 ) between the load member 51 and the corresponding electrode finger 411 a, 411 b, or 421 in the surface acoustic wave resonator according to Example 1 to 0. That is, in the surface acoustic wave resonator according to Comparative Example 2, the x-coordinate of the center of the length of the load member 51 along the x-axis coincides with the x-coordinate of the center of the length of the corresponding electrode finger 411 a, 411 b, or 421 along the x-axis.

[0073] 7, in the frequency range of 720-760 MHz where longitudinal modes occur, the surface acoustic wave resonator according to Example 1 can suppress phase fluctuations more effectively than the surface acoustic wave resonator according to Comparative Example 2 (see the area surrounded by the dashed line). In other words, the surface acoustic wave resonator according to Example 1 can suppress the longitudinal modes more effectively than the surface acoustic wave resonator according to Comparative Example 2, thereby suppressing ripples caused by the longitudinal modes.

[0074] 8 is a graph showing the resonance characteristics of the surface acoustic wave resonators according to Example 1 and Comparative Example 3. In FIG. 8, the horizontal axis represents frequency, and the vertical axis represents attenuation.

[0075] The surface acoustic wave resonator according to Comparative Example 3 is obtained by removing the load members 51 that overlap with the plurality of electrode fingers 411 a and 411 b of the IDT electrode 41 from the surface acoustic wave resonator according to Example 1. In other words, the plurality of load members 51 of the surface acoustic wave resonator according to Comparative Example 3 overlap only with the plurality of electrode fingers 421 of the reflecting electrode 42 out of the plurality of electrode fingers 411 a, 411 b, and 421 of the IDT electrode 41 and the reflecting electrode 42.

[0076] 8, in the frequency range of 840-880 MHz where stop band ripple occurs, the surface acoustic wave resonator according to Example 1 can suppress the fluctuation in attenuation more effectively than the surface acoustic wave resonator according to Comparative Example 3 (see the region surrounded by the dashed line). In other words, the surface acoustic wave resonator according to Example 1 can suppress the stop band ripple more effectively than the surface acoustic wave resonator according to Comparative Example 3.

[0077] 9 is a graph showing frequency characteristics of the Q value of the surface acoustic wave resonators according to Example 2 and Comparative Example 4. In FIG. 9, the horizontal axis represents frequency, and the vertical axis represents the Q value.

[0078] The surface acoustic wave resonator according to Comparative Example 4 is obtained by making the thickness of the load member 51 on the side surfaces of the electrode fingers (for example, thickness t51b in FIG. 3 ) equal to the thickness of the load member 51 on the top surface (for example, thickness t51a in FIG. 3 ) in the surface acoustic wave resonator according to Example 2. In other words, the multiple load members 51 of the surface acoustic wave resonator according to Comparative Example 4 cover the top and side surfaces of the 20 electrode fingers 411 a and 411 b of the IDT electrode 41 with approximately the same thickness.

[0079] 9, the Q value of the surface acoustic wave resonator according to Example 2 is improved compared to the surface acoustic wave resonator according to Comparative Example 4. In particular, the Q value is improved in the frequency range of 800-840 MHz.

[0080] [1.5 Summary] As described above, the surface acoustic wave resonator 1 according to this embodiment includes the substrate 3 including the piezoelectric layer 31, at least one electrode 4 arranged on the substrate 3 and including the IDT electrode 41, and a plurality of load members 51 made of a dielectric material and arranged spaced apart from one another on or within the substrate 3, wherein the at least one electrode 4 includes a plurality of electrode fingers 411 a, 411 b, and 421 aligned along the x-axis on the substrate 3, the plurality of electrode fingers 411 a, 411 b, and 421 extending along a y-axis perpendicular to the x-axis, and each of the plurality of load members 51 at least partially overlaps with at least one corresponding electrode finger in a plan view of the substrate 3, and the electrode fingers arranged in the first sub-region 3 b 1 that overlap with the plurality of load members 51 are the number of electrode fingers 411a, 411b, and 421 overlapping with the load members 51 among the electrode fingers arranged in the third sub-region 3b3 is greater than the number of electrode fingers arranged in the second sub-region 3b2 that overlap with the load members 51, respectively; the first sub-region 3b1, the second sub-region 3b2, and the third sub-region 3b3 are obtained by equally dividing the electrode finger region 3b on the substrate 3, in which the electrode fingers 411a, 411b, and 421 are arranged, in the y-axis direction; the second sub-region 3b2 is located between the first sub-region 3b1 and the third sub-region 3b3; and the load members 51 include two or more load members 51 overlapping with the electrode fingers arranged in the first sub-region 3b1 and two or more load members 51 overlapping with the electrode fingers arranged in the third sub-region 3b3.

[0081] This allows the reflectivity to be improved by adding mass to the plurality of electrode fingers 411a, 411b, and 421 arranged in the first sub-region 3b1 and the third sub-region 3b3 using the plurality of load members 51, thereby improving the effect of confining surface acoustic waves within the surface acoustic wave resonator 1. As a result, as shown in Fig. 6, the Q value of the surface acoustic wave resonator 1 can be improved. Furthermore, because the plurality of load members 51 are made of a dielectric, it is easier to ensure a distance between adjacent electrode fingers than when the plurality of load members 51 are made of a conductor, and a decrease in power durability can be suppressed.

[0082] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, at least one electrode 4 may further include a pair of reflecting electrodes 42, and the IDT electrode 41 may be disposed between the pair of reflecting electrodes 42.

[0083] This makes it possible to further improve the effect of confining the surface acoustic waves within the surface acoustic wave resonator 1 by the pair of reflecting electrodes 42, thereby further improving the Q value of the surface acoustic wave resonator 1.

[0084] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, at least one of the multiple load members 51 may at least partially overlap with at least one corresponding electrode finger of the IDT electrode 41 in a planar view of the substrate 3, and at least another of the multiple load members 51 may at least partially overlap with at least one corresponding electrode finger of the reflecting electrode 42 in a planar view of the substrate 3.

[0085] According to this, the multiple load members 51 overlap with the electrode fingers 411a, 411b, and 421 of both the IDT electrode 41 and the reflective electrode 42, and therefore, as shown in Figure 8, the stop band ripple can be suppressed compared to when the multiple load members 51 overlap only with the electrode fingers 421 of the reflective electrode 42.

[0086] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the plurality of load members 51 may correspond one-to-one to some of the plurality of electrode fingers 411 a , 411 b , and 421 .

[0087] This allows for more precise adjustment of the positional relationship (e.g., the area of ​​overlap) between the multiple load members 51 and the multiple electrode fingers 411a, 411b, or 421, thereby improving the characteristics of the surface acoustic wave resonator 1.

[0088] Furthermore, for example, in the surface acoustic wave resonator 1 according to this preferred embodiment, each of the plurality of load members 51 may overlap a portion of a corresponding electrode finger in a plan view of the substrate 3 .

[0089] This allows each of the plurality of load members 51 to overlap a part of the corresponding electrode finger, thereby suppressing the longitudinal mode and reducing ripples caused by the longitudinal mode.

[0090] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the midpoint of the length along the x-axis of each of the multiple load members 51 may be shifted toward the center of the IDT electrode 41 along the x-axis with respect to the midpoint of the length along the x-axis of the corresponding electrode finger.

[0091] This allows each of the multiple load members 51 to be shifted toward the center of the IDT electrode 41 with respect to the corresponding electrode finger, thereby suppressing the longitudinal mode and reducing ripples caused by the longitudinal mode, as shown in FIG. 7.

[0092] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the plurality of load members 51 may be a plurality of load films arranged on the substrate 3, and the plurality of load films may at least partially cover some of the plurality of electrode fingers 411 a, 411 b, and 421.

[0093] This allows multiple load films arranged on the substrate 3 to be used as multiple load members 51, making it possible to manufacture the surface acoustic wave resonator 1 relatively more easily than when multiple load members 51 are arranged within the substrate 3.

[0094] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, for each of the multiple load members 51, the thickness of the load member 51 on the top surface of the corresponding electrode finger may be greater than the thickness of the load member 51 on the side surface of the corresponding electrode finger.

[0095] This makes it possible to improve the Q value of the surface acoustic wave resonator 1, as shown in FIG.

[0096] Furthermore, for example, the surface acoustic wave resonator 1 according to this embodiment may further include a protective film 52 disposed on the substrate 3 and covering the substrate 3 and at least a portion of the plurality of electrode fingers 411 a , 411 b , and 421 .

[0097] This allows multiple load members 51 (multiple load films) and protective film 52 to be arranged on the substrate 3, and in addition to improving the Q value of the surface acoustic wave resonator 1 by the multiple load members 51, the protective film 52 can improve the characteristics (e.g., temperature characteristics) of the surface acoustic wave resonator 1.

[0098] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the protective film 52 may be stacked on a plurality of load members 51 .

[0099] In this structure, the protective film 52 is stacked on a plurality of load members 51 (a plurality of load films). Even with this structure, the Q value of the surface acoustic wave resonator 1 can be improved.

[0100] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the plurality of load members 51 may be made of a material different from that of the protective film 52 .

[0101] This allows suitable materials to be used for the load members 51 and the protective films 52, respectively, which simplifies the manufacture of the surface acoustic wave resonator 1 and further improves the Q value.

[0102] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the plurality of load members 51 may be made of tantalum pentoxide, niobium pentoxide, tungsten (VI) oxide, silicon nitride, titanium (IV) oxide, cerium (IV) oxide, hafnium (IV) oxide, or ytterbium (III) oxide, and the protective film 52 may be made of silicon dioxide or silicon nitride.

[0103] In this way, the load members 51 are made of a material having a higher density than the protective film 52, so that the load members 51 can be made thinner, thereby simplifying the manufacture of the surface acoustic wave resonator 1.

[0104] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the distance between an electrode finger that overlaps with a plurality of load members 51 and an electrode finger adjacent to that electrode finger that does not overlap with a plurality of load members 51 may be different from the distance between two adjacent electrode fingers that overlap with a plurality of load members 51, or from the distance between two adjacent electrode fingers that do not overlap with a plurality of load members 51.

[0105] This makes it possible to suppress the longitudinal mode, and to suppress ripples caused by the longitudinal mode.

[0106] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the duty ratio of two or more electrode fingers that overlap with a plurality of load members 51 may be different from the duty ratio of two or more electrode fingers that do not overlap with any of the plurality of load members 51.

[0107] This allows the duty ratios of the plurality of electrode fingers to be set in accordance with the relationship with the load member 51, thereby enabling further improvement in the Q value.

[0108] For example, in the surface acoustic wave resonator 1 according to this embodiment, the pitch of two or more electrode fingers 411a, 411b, and 421 that overlap with a plurality of load members 51 may be different from the pitch of two or more electrode fingers 411a, 411b, and 421 that do not overlap with any of the plurality of load members 51.

[0109] This allows the pitch of the plurality of electrode fingers to be set in accordance with the relationship with the load member 51, thereby enabling further improvement of the Q value.

[0110] For example, in the surface acoustic wave resonator 1 according to this embodiment, the width of at least one of the two or more electrode fingers 411a, 411b, and 421 that do not overlap any of the multiple load members 51 may be different from the width of at least one other of the two or more electrode fingers 411a, 411b, and 421 that do not overlap any of the multiple load members 51.

[0111] This allows the widths of two or more electrode fingers that do not overlap any of the plurality of load members 51 to be individually set, thereby enabling a further improvement in the Q value.

[0112] For example, in the surface acoustic wave resonator 1 according to this embodiment, the spacing between adjacent electrode fingers of at least one set of the two or more electrode fingers 411a, 411b, and 421 that do not overlap any of the multiple load members 51 may be different from the spacing between adjacent electrode fingers of at least another set of the two or more electrode fingers 411a, 411b, and 421 that do not overlap any of the multiple load members 51.

[0113] This allows the spacing between adjacent electrode fingers among two or more electrode fingers that do not overlap any of the plurality of load members 51 to be individually set, thereby enabling further improvement of the Q value.

[0114] Furthermore, for example, in the surface acoustic wave resonator 1 according to this embodiment, the spacing between adjacent electrode fingers in multiple sets of two or more electrode fingers 411a, 411b, and 421 that do not overlap any of the multiple load members 51 may be different from each other.

[0115] This allows the spacing between adjacent electrode fingers among two or more electrode fingers that do not overlap any of the plurality of load members 51 to be individually set, thereby enabling further improvement of the Q value.

[0116] Furthermore, the surface acoustic wave resonator 1 according to this embodiment includes a substrate 3 including a piezoelectric layer 31, at least one electrode 4 disposed on the substrate 3 and including an IDT electrode 41, and a dielectric film 5 disposed on the at least one electrode 4, wherein the at least one electrode 4 includes a plurality of electrode fingers 411 a, 411 b, and 421 aligned along the x-axis on the substrate 3, the plurality of electrode fingers 411 a, 411 b, and 421 extending along a y-axis perpendicular to the x-axis, and the dielectric film 5 on the electrode fingers disposed in the first sub-region 3 b 1 The average thickness of the dielectric film 5 on the electrode fingers arranged in the third sub-region 3b3 and the average thickness of the dielectric film 5 on the electrode fingers arranged in the second sub-region 3b2 are each greater than the average thickness of the dielectric film 5 on the electrode fingers arranged in the second sub-region 3b2, and the first sub-region 3b1, the second sub-region 3b2 and the third sub-region 3b3 are obtained by equally dividing the electrode finger region 3b on the substrate 3 in the y-axis direction, in which multiple electrode fingers 411a, 411b and 421 are arranged, and the second sub-region 3b2 is located between the first sub-region 3b1 and the third sub-region 3b3.

[0117] This allows mass to be added to the plurality of electrode fingers 411a, 411b, and 421 arranged in the first sub-region 3b1 and the third sub-region 3b3 by the thicker dielectric film 5. This improves reflectivity and the effect of confining surface acoustic waves within the surface acoustic wave resonator 1. As a result, as shown in FIG. 6 , the Q value of the surface acoustic wave resonator 1 can be improved. Furthermore, because mass can be added by a dielectric, it is easier to ensure the distance between adjacent electrode fingers than when mass is added by a conductor, and a decrease in power durability can be suppressed.

[0118] (Variation 1 of Embodiment 1) Next, Variation 1 of Embodiment 1 will be described. This variation is different from Embodiment 1 mainly in that a plurality of load members 51A are arranged in the substrate 3 instead of the plurality of load members 51. This variation will be described below with reference to FIG. 10 , focusing on the differences from Embodiment 1.

[0119] Fig. 10 is a cross-sectional view of a surface acoustic wave resonator 1 according to this modification. Note that Fig. 10 is intended to illustrate a typical configuration of the surface acoustic wave resonator 1, and the configuration of the surface acoustic wave resonator 1 is not limited to that shown in Fig. 10. Therefore, the following description of the surface acoustic wave resonator 1 should not be interpreted in a restrictive manner.

[0120] The surface acoustic wave resonator 1 includes a substrate 3, a plurality of electrodes 4, a dielectric film 5A, and a load member 51A.

[0121] The dielectric film 5A is disposed on the substrate 3 and covers the substrate 3 and the plurality of electrodes 4. The dielectric film 5A includes a protective film 52 but does not include the plurality of load members. In this modification, the surface acoustic wave resonator 1 does not necessarily have to include the dielectric film 5A.

[0122] The multiple load members 51A are an example of multiple first load members and are made of a dielectric. In this modification, the multiple load members 51A are arranged spaced apart from one another within the substrate. Each of the multiple load members 51A at least partially overlaps with at least one corresponding electrode finger in a plan view of the substrate 3. This allows the multiple load members 51A to add mass to some of the multiple electrode fingers 411a, 411b, and 421.

[0123] The load members 51A are made of a material having a higher density than the low sound velocity layer 32, and specifically, tantalum pentoxide (Ta ２ O ５ ), silicon dioxide, silicon nitride, alumina, or any combination thereof may be used, but is not limited to these.

[0124] The multiple load members 51A may be arranged in a layer different from the low acoustic velocity layer 32 in the substrate 3. For example, the multiple load members 51A may be arranged in the piezoelectric layer 31, the high acoustic velocity layer 33, or the support substrate 34.

[0125] As described above, in the surface acoustic wave resonator 1 according to this modified example, the plurality of load members 51A may be disposed within the substrate 3.

[0126] With this, the load members 51A do not come into contact with the electrode fingers 411a, 411b, and 421, and therefore the Q value can be improved while suppressing fluctuations in the characteristics of the surface acoustic wave resonator 1.

[0127] For example, in the surface acoustic wave resonator 1 according to this modified example, the substrate 3 may further include a low acoustic velocity layer 32 in which the acoustic velocity of the propagating bulk waves is slower than the acoustic velocity of the elastic waves propagating through the piezoelectric layer 31, and the piezoelectric layer 31 may be disposed on the low acoustic velocity layer 32, and the plurality of load members 51A may be disposed within the low acoustic velocity layer 32.

[0128] This allows a plurality of load members 51A to be arranged within the low acoustic velocity layer 32, and even in this case, the Q value can be improved.

[0129] (Variation 2 of Embodiment 1) Next, Variation 2 of Embodiment 1 will be described. This variation is mainly different from Embodiment 1 in that one load member 51 overlaps with multiple electrode fingers. This variation will be described below with reference to FIG. 11 , focusing on the differences from Embodiment 1.

[0130] Fig. 11 is a plan view of the electrodes 4 and the load members 51B according to this modification. Specifically, Fig. 11 is a view of the electrodes 4 and the load members 51B orthogonally projected onto the xy plane.

[0131] 11 is intended to illustrate a typical positional relationship between the electrodes 4 and the load members 51B, and the positional relationship between the electrodes 4 and the load members 51B is not limited to the positional relationship shown in FIG. 11. Therefore, the following description of the electrodes 4 and the load members 51B should not be construed as limiting.

[0132] The multiple load members 51B are an example of multiple first load members and are made of a dielectric. In this modification, the multiple load members 51B are multiple load films (an example of multiple first load films) arranged apart from each other on the substrate 3, similar to the multiple load members 51 in embodiment 1. Each of the multiple load members 51B at least partially overlaps with at least two corresponding electrode fingers in a plan view of the substrate 3. This allows the multiple load members 51B to add mass to some of the multiple electrode fingers 411a, 411b, and 421. The multiple load members 51B can be made of the same material as the multiple load members 51 in embodiment 1.

[0133] In this modification, each of the plurality of load members 51B at least partially overlaps with the corresponding two electrode fingers 411a and 411b or 421 in a plan view of the substrate 3. In Fig. 11 , each of the two load members 51B at least partially overlaps with the corresponding two electrode fingers 411a and 411b in a plan view of the substrate 3. Furthermore, each of the other two plurality of load members 51B at least partially overlaps with the corresponding two electrode fingers 421.

[0134] As described above, in the surface acoustic wave resonator 1 according to this modification, each of the plurality of load members 51B may at least partially overlap with the corresponding plurality of electrode fingers in a plan view of the substrate 3.

[0135] Even in this case, the Q value of the surface acoustic wave resonator 1 can be improved, as in the first embodiment.

[0136] (Third Modification of First Embodiment) Next, a third modification of the first embodiment will be described. This modification is different from the first embodiment mainly in that the surface acoustic wave resonator does not include a pair of reflecting electrodes. This modification will be described below with reference to FIG. 12 , focusing on the differences from the first embodiment.

[0137] Fig. 12 is a plan view of an electrode 4C and a plurality of load members 51C according to this modification. Specifically, Fig. 12 is a view of the electrode 4C and the plurality of load members 51C orthogonally projected onto the xy plane.

[0138] 12 is intended to illustrate a typical positional relationship between the electrode 4C and the plurality of load members 51C, and the positional relationship between the electrode 4C and the plurality of load members 51C is not limited to the positional relationship illustrated in FIG. 12. Therefore, the following description of the electrode 4C and the plurality of load members 51C should not be construed as limiting.

[0139] The electrode 4C includes an IDT electrode 41 and is disposed on the substrate 3. In this modification, the electrode 4C does not include a pair of reflective electrodes 42.

[0140] The multiple load members 51C are an example of multiple first load members and are made of a dielectric. In this modification, the multiple load members 51C are multiple load films (an example of multiple first load films) arranged apart from each other on the substrate 3, similar to the multiple load members 51 in embodiment 1. Each of the multiple load members 51C at least partially overlaps with at least one corresponding electrode finger in a plan view of the substrate 3. This allows the multiple load members 51C to add mass to some of the multiple electrode fingers 411a and 411b. The multiple load members 51C can be made of the same material as the multiple load members 51 in embodiment 1.

[0141] As described above, in the surface acoustic wave resonator 1 according to this modification, the electrode 4C does not necessarily have to include the reflective electrode 42.

[0142] Even in such a case, the surface acoustic wave resonator 1 can improve the Q value in the same way as in the first embodiment.

[0143] (Fourth Modification of First Embodiment) Next, a fourth modification of the first embodiment will be described. This modification is different from the first embodiment mainly in that the tips of the electrode fingers 411 a and 411 b of the IDT electrode 41 overlap with another load member. This modification will be described below with reference to FIGS. 13 and 14, focusing on the differences from the first embodiment.

[0144] Fig. 13 is a plan view of the electrodes 4 and the load members 51D, 53a, and 53b according to this modification. Specifically, Fig. 13 is a view in which the electrodes 4 and the load members 51D, 53a, and 53b are orthogonally projected onto the xy plane.

[0145] 14 is a partial cross-sectional view of the surface acoustic wave resonator 1 according to this modified example. Specifically, Fig. 14 is a cross-section taken along line xiv-xiv in Fig. 13.

[0146] 13 and 14 are intended to illustrate a typical positional relationship between the electrodes 4 and the load members 51D, 53a, and 53b, and the positional relationship between the electrodes 4 and the load members 51D, 53a, and 53b is not limited to the positional relationship shown in Fig. 13 and 14. Therefore, the following description of the electrodes 4 and the load members 51D, 53a, and 53b should not be construed as limiting.

[0147] The multiple load members 51D are an example of multiple first load members and are made of a dielectric. In this modification, the multiple load members 51D are multiple load films (an example of multiple first load films) arranged apart from each other on the substrate 3, similar to the multiple load members 51 in embodiment 1. Each of the multiple load members 51D at least partially overlaps with at least one corresponding electrode finger in a plan view of the substrate 3. This allows the multiple load members 51D to add mass to some of the multiple electrode fingers 421. The multiple load members 51D can be made of the same material as the multiple load members 51 in embodiment 1.

[0148] The multiple load members 53a and 53b are an example of multiple second load members and are made of a dielectric or a conductor. The multiple load members 53a and 53b are multiple load films (an example of multiple second load films) arranged on the substrate 3. The load member 53a at least partially overlaps the tips of the multiple electrode fingers 411a in a planar view of the substrate 3. The load member 53b at least partially overlaps the tips of the multiple electrode fingers 411b in a planar view of the substrate 3. This allows the multiple load members 53a and 53b to add mass to the tips of the multiple electrode fingers 411a and 411b of the IDT electrode 41. The load members 53a and 53b can be made of the same material as the multiple load members 51D. Note that the material of the load members 53a and 53b may be different from the material of the load member 51D.

[0149] 14 , the thickness t53 of the load member 53b on the plurality of electrode fingers 411b is smaller than the thickness t51a of the load member 51D on the plurality of electrode fingers 421. Similarly, the thickness of the load member 53a on the plurality of electrode fingers 411a is also smaller than the thickness t51a of the load member 51D on the plurality of electrode fingers 421. In other words, the thickness of the plurality of load members 51D is larger than the thicknesses of the plurality of load members 53a and 53b. Here, the thickness of the load member is calculated as the average thickness of the load members on the top surfaces of the plurality of electrode fingers.

[0150] The thickness of the plurality of load members 51D may be the same as the thickness of the plurality of load members 53a and 53b. The fact that the thicknesses of two objects are the same does not mean that they are strictly the same, but rather that an error within a range (±10%) that is considered to be substantially the same is allowed.

[0151] As described above, the surface acoustic wave resonator 1 according to this modified example may further include a plurality of load members 53 a and 53 b that at least partially overlap the tips of the electrode fingers 411 a and 411 b of the IDT electrode 41 among the plurality of electrode fingers 411 a, 411 b, and 421 when viewed in a plane of the substrate 3.

[0152] According to this, the transverse mode can be further suppressed by the piston mode, thereby suppressing ripples caused by the transverse mode.

[0153] Furthermore, for example, in the surface acoustic wave resonator 1 according to this modified example, the plurality of load members 51D may be a plurality of first load films arranged on the substrate 3, and the plurality of load members 53a and 53b may be a plurality of second load films made of the same material as the plurality of load members 51D and arranged on the substrate 3.

[0154] This allows the plurality of load members 51D and the plurality of load members 53a and 53b to be formed from the same material, thereby simplifying the manufacturing process of the surface acoustic wave resonator 1.

[0155] Furthermore, for example, in the surface acoustic wave resonator 1 according to this modified example, the thickness of the plurality of load members 51D may be the same as the thickness of the plurality of load members 53a and 53b.

[0156] This allows the plurality of load members 51D and the plurality of load members 53a and 53b to be formed in a single process, thereby further simplifying the manufacturing process of the surface acoustic wave resonator 1.

[0157] Furthermore, for example, in the surface acoustic wave resonator 1 according to this modified example, the thickness of the plurality of load members 51D may be greater than the thickness of the plurality of load members 53a and 53b.

[0158] This allows the multiple load members 51D for improving the Q value and the multiple load members 53a and 53b for suppressing transverse modes to have thicknesses suited to their respective purposes. In particular, by making the multiple load members 51D for improving the Q value thicker than the multiple load members 53a and 53b for suppressing transverse modes, the Q value can be further improved.

[0159] (Fifth Modification of First Embodiment) Next, a fifth modification of the first embodiment will be described. This modification is different from the first embodiment mainly in that an IDT electrode and a reflective electrode are disposed on both sides of the piezoelectric layer 31. This modification will be described below with reference to FIGS. 1, 15, and 16, focusing on the differences from the first embodiment.

[0160] Fig. 15 is a plan view of the surface acoustic wave resonator 1 according to this modification, seen from the positive side of the z-axis toward the main surface 31b of the piezoelectric layer 31. Fig. 16 is a cross-sectional view of the surface acoustic wave resonator 1 according to this modification. The cross section of the surface acoustic wave resonator 1 in Fig. 16 is taken along line xvi-xvi in ​​Fig. 15.

[0161] The piezoelectric layer 31 has two opposing principal surfaces 31a and 31b. The principal surface 31a is an example of a first principal surface, and the principal surface 31b is an example of a second principal surface. A plurality of electrodes 4 are arranged on the principal surface 31a as shown in FIG. 1, and a plurality of electrodes 6 are arranged on the principal surface 31b as shown in FIG.

[0162] The plurality of electrodes 6 are an example of at least one second electrode, and include an IDT electrode 61 and a pair of reflective electrodes 62 .

[0163] The IDT electrode 61 is an example of a second IDT electrode, and includes two interdigitated comb electrodes arranged on the piezoelectric layer 31, and can convert an electrical signal into a surface acoustic wave and vice versa. The IDT electrode 61 includes a plurality of electrode fingers 611 a and 611 b and bus bar electrodes 612 a and 612 b.

[0164] The electrode fingers 611a and 611b are an example of a plurality of second electrode fingers, and are arranged alternately along the x-axis (second axis) and extend along the y-axis (second axis). One ends of the electrode fingers 611a are connected to the bus bar electrode 612a and extend from the bus bar electrode 612a in the negative direction of the y-axis. One ends of the electrode fingers 611b are connected to the bus bar electrode 612b and extend from the bus bar electrode 612b in the positive direction of the y-axis. The electrode fingers 611a and 611b do not have to be arranged alternately one by one, and may be arranged alternately in groups of two or more, for example.

[0165] In a plan view of the substrate 3, the plurality of electrode fingers 611a and 611b overlap one-to-one with the plurality of electrode fingers 411a and 411b. The plurality of electrode fingers 411a and the plurality of electrode fingers 611a are excited in phase, and the plurality of electrode fingers 411b and the plurality of electrode fingers 611b are excited in phase. This makes it possible to suppress spurious signals such as higher-order modes. In a plan view of the substrate 3, the plurality of electrode fingers 611a and 611b do not have to completely overlap with the plurality of electrode fingers 411a and 411b. For example, some of the plurality of electrode fingers 611a and 611b may not overlap with the plurality of electrode fingers 411a and 411b, and some of the plurality of electrode fingers 411a and 411b may not overlap with the plurality of electrode fingers 611a and 611b.

[0166] The busbar electrode 612a extends along the x-axis and is connected to one end of each of the electrode fingers 611a. The busbar electrode 612a is arranged parallel to the busbar electrode 612b and spaced apart from the busbar electrode 612b in the positive direction of the y-axis.

[0167] The busbar electrode 612b extends along the x-axis and is connected to one end of each of the electrode fingers 611b. The busbar electrode 612b is arranged parallel to the busbar electrode 612a and spaced apart from the busbar electrode 612a in the negative direction of the y-axis.

[0168] The pair of reflective electrodes 62 are an example of a pair of second reflective electrodes, and are arranged to sandwich the IDT electrode 61 in the x-axis direction in order to confine within the IDT electrode 61 a predetermined high-frequency signal that resonates in the IDT electrode 61. In other words, the IDT electrode 61 is arranged between the pair of reflective electrodes 62 in the x-axis direction. Each of the pair of reflective electrodes 62 includes a plurality of electrode fingers 621 and bus bar electrodes 622 a and 622 b.

[0169] The multiple electrode fingers 621 are an example of multiple second electrode fingers, and are aligned along the x-axis and extend along the y-axis. Both ends of the multiple electrode fingers 621 are connected to busbar electrodes 622a and 622b. The busbar electrode 622a extends along the x-axis and is connected to one end of the multiple electrode fingers 621. The busbar electrode 622b extends along the x-axis, is arranged parallel to and opposite the busbar electrode 622a, and is connected to the other end of the multiple electrode fingers 621.

[0170] The IDT electrode 61 and the pair of reflective electrodes 62 may be made of, for example, aluminum, titanium, gold, silver, copper, platinum, tungsten, molybdenum, ruthenium, or any combination thereof. Note that the materials for the IDT electrode 61 and the pair of reflective electrodes 62 are not limited to these. Furthermore, the materials for the IDT electrode 61 and the pair of reflective electrodes 62 may be different from each other or the same.

[0171] The multiple load members 71 are an example of multiple third load members and are made of a dielectric. In this embodiment, the multiple load members 71 are multiple load films (an example of multiple first load films) arranged apart from each other on the substrate 3. Each of the multiple load members 71 at least partially overlaps with at least one corresponding electrode finger in a plan view of the substrate 3. This allows the multiple load members 71 to add mass to some of the multiple electrode fingers 611 a, 611 b, and 621.

[0172] The load members 71 are made of a dielectric material, specifically, tantalum pentoxide (Ta ２ O ５ ), niobium pentoxide (Nb ２ O ５), tungsten(VI) oxide (WO ３ ), silicon nitride (SiN), titanium oxide (IV) (TiO ２ ), cerium (IV) oxide (CeO ２ ), hafnium (IV) oxide (HfO ２ ), ytterbium(III) oxide (Yb ２ O ３ ), silicon dioxide, alumina, or any combination thereof can be used, but is not limited to these. By using a dielectric material having a higher density than the protective film 52 as the material for the multiple load members 71, the multiple load members 71 can be made thinner. Note that the multiple load members 71 may be made of different materials.

[0173] The electrode finger region 3b on the principal surfaces 31a and 31b of the piezoelectric layer 31 is a region in which a plurality of electrode fingers 411a, 411b, 421, 611a, 611b, and 621 are arranged, and is equally divided into a first subregion 3b1, a second subregion 3b2, and a third subregion 3b3 in the y-axis direction. The electrode finger region 3b is defined as a rectangular region that encloses the plurality of electrode fingers 411a, 411b, 421, 611a, 611b, and 621 with the minimum area. In FIGS. 1 and 15 , the first subregion 3b1, the second subregion 3b2, and the third subregion 3b3 are the left, center, and right partial regions of the electrode finger region 3b, respectively. The second subregion 3b2 is located between the first subregion 3b1 and the third subregion 3b3.

[0174] The cross-sectional configuration and arrangement of the plurality of electrode fingers 611a, 611b, 621 and the plurality of load members 71 are the same as those in the first embodiment, and therefore illustration and description thereof will be omitted.

[0175] 1, 15, and 16. For example, the surface acoustic wave resonator 1 may include only one of the plurality of load members 51 and 71. In other words, a load member may be superimposed on only one of the plurality of electrodes 4 arranged on the main surface 31a and the plurality of electrodes 6 arranged on the main surface 31b.

[0176] As described above, in the surface acoustic wave resonator 1 according to this modification, the piezoelectric layer 31 may include principal surfaces 31 a and 31 b facing each other, and at least one electrode 4 may be arranged on one of the principal surfaces 31 a and 31 b. The surface acoustic wave resonator 1 may further include at least one electrode 6 including an IDT electrode 61, which is arranged on the other of the principal surfaces 31 a and 31 b. The at least one electrode 6 may include a plurality of electrode fingers 611 a, 611 b, and 621 aligned along the x-axis on the substrate 3 and extending respectively along the y-axis perpendicular to the x-axis. The plurality of electrode fingers 611 a, 611 b, and 621 may overlap one-to-one with the plurality of electrode fingers 411 a, 411 b, and 421 in a planar view of the substrate 3.

[0177] As a result, the plurality of electrode fingers 611a and the plurality of electrode fingers 411a are excited in phase, and the plurality of electrode fingers 611b and the plurality of electrode fingers 411b are excited in phase, thereby making it possible to suppress spurious responses such as higher-order modes.

[0178] For example, the surface acoustic wave resonator 1 according to this modified example may further include a plurality of load members 71 made of a dielectric and arranged spaced apart from one another on or within the substrate 3, each of which may at least partially overlap with at least one corresponding electrode finger in a planar view of the substrate 3, and the number of electrode fingers arranged in the first sub-region 3b1 that overlap with the plurality of load members 71 and the number of electrode fingers arranged in the third sub-region 3b3 that overlap with the plurality of load members 71 may each be greater than the number of electrode fingers arranged in the second sub-region 3b2 that overlap with the plurality of load members 71, and the plurality of load members 71 may include two or more load members 71 that overlap with the electrode fingers arranged in the first sub-region 3b1 and two or more load members 71 that overlap with the electrode fingers arranged in the third sub-region 3b3.

[0179] This allows the reflectivity to be improved by adding mass to the plurality of electrode fingers 611a, 611b, and 621 arranged in the first sub-region 3b1 and the third sub-region 3b3 using the plurality of load members 71, thereby improving the effect of confining surface acoustic waves within the surface acoustic wave resonator 1. As a result, it is possible to improve the Q value of the surface acoustic wave resonator 1. Furthermore, because the plurality of load members 71 are made of a dielectric, it is easier to ensure a distance between adjacent electrode fingers than when the plurality of load members 71 are made of a conductor, and it is possible to suppress a decrease in power durability.

[0180] Furthermore, for example, in the surface acoustic wave resonator 1 according to this modified example, at least one electrode 6 may further include a pair of reflecting electrodes 62, and the IDT electrode 61 may be disposed between the pair of reflecting electrodes 62.

[0181] This makes it possible to further improve the effect of confining the surface acoustic waves within the surface acoustic wave resonator 1 by the pair of reflecting electrodes 62, thereby further improving the Q value of the surface acoustic wave resonator 1.

[0182] Second Embodiment Next, a second embodiment will be described. In this embodiment, a surface acoustic wave filter using the surface acoustic wave resonator 1 according to the first embodiment or a modification thereof will be described with reference to FIGS. 17 and 18.

[0183] 17 is a circuit diagram of a surface acoustic wave filter 100 according to this embodiment. Note that Fig. 17 is intended to illustrate a typical circuit configuration of the surface acoustic wave filter 100, and the circuit configuration of the surface acoustic wave filter 100 is not limited to the circuit configuration shown in Fig. 17. Therefore, the following description of the surface acoustic wave filter 100 should not be interpreted in a restrictive manner.

[0184] The surface acoustic wave filter 100 is a ladder-type surface acoustic wave filter, and includes a plurality of series arm resonators 101 to 104 and a plurality of parallel arm resonators 111 to 114.

[0185] The plurality of series arm resonators 101 to 104 are connected in series between an input terminal 121 and an output terminal 122. Specifically, one end of the series arm resonator 101 is connected to the input terminal 121, and the other end of the series arm resonator 101 is connected to one end of the series arm resonator 102. The other end of the series arm resonator 102 is connected to one end of the series arm resonator 103. The other end of the series arm resonator 103 is connected to one end of the series arm resonator 104. The other end of the series arm resonator 104 is connected to the output terminal 122.

[0186] The multiple parallel arm resonators 111 to 114 are connected in parallel between a path connecting the input terminal 121 and the output terminal 122 and ground. Specifically, the parallel arm resonator 111 is connected between the path connecting the series arm resonators 101 and 102 and ground. The parallel arm resonator 112 is connected between the path connecting the series arm resonators 102 and 103 and ground. The parallel arm resonator 113 is connected between the path connecting the series arm resonators 103 and 104 and ground. The parallel arm resonator 114 is connected between the path connecting the series arm resonator 104 and the output terminal 122 and ground.

[0187] In this embodiment, at least one of the plurality of series arm resonators 101 to 104 and the plurality of parallel arm resonators 111 to 114 is the surface acoustic wave resonator 1 according to the first embodiment or its modification.

[0188] For example, of the plurality of series arm resonators 101 to 104 and the plurality of parallel arm resonators 111 to 114, only the plurality of parallel arm resonators 111 to 114 may include the surface acoustic wave resonator 1. In other words, the plurality of parallel arm resonators 111 to 114 may include the surface acoustic wave resonator 1, and the plurality of series arm resonators 101 to 104 may not include the surface acoustic wave resonator 1.

[0189] Furthermore, when the plurality of series arm resonators 101 to 104 include a surface acoustic wave resonator 1 and the plurality of parallel arm resonators 111 to 114 include a surface acoustic wave resonator 1, the number, shape, size, or any combination thereof of the plurality of load members 51, 51A, 51B, 51C, or 51D may differ between the surface acoustic wave resonators 1 included in the plurality of series arm resonators 101 to 104 and the surface acoustic wave resonators 1 included in the plurality of parallel arm resonators 111 to 114.

[0190] For example, in the surface acoustic wave resonator 1 included in the plurality of series arm resonators 101 to 104, the area of ​​the portion where the plurality of load members 51, 51A, 51B, 51C, or 51D overlap with the plurality of electrode fingers may be smaller than the area of ​​the portion where the plurality of load members 51, 51A, 51B, 51C, or 51D overlap with the plurality of electrode fingers in the surface acoustic wave resonator 1 included in the plurality of parallel arm resonators 111 to 114.

[0191] Furthermore, for example, the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the surface acoustic wave resonators 1 included in the plurality of series arm resonators 101 to 104 may be smaller than the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the surface acoustic wave resonators 1 included in the plurality of parallel arm resonators 111 to 114.

[0192] Furthermore, for example, the thicknesses of the load members 51, 51A, 51B, 51C, or 51D of the surface acoustic wave resonators 1 included in the series arm resonators 101 to 104 may be smaller than the thicknesses of the load members 51, 51A, 51B, 51C, or 51D of the surface acoustic wave resonators 1 included in the parallel arm resonators 111 to 114.

[0193] Furthermore, when each of the two or more series arm resonators is a surface acoustic wave resonator 1, the number, shape, size, or any combination thereof of the multiple load members 51, 51A, 51B, 51C, or 51D may vary depending on the distance from the input terminal 121.

[0194] For example, when each of the two or more series arm resonators is a surface acoustic wave resonator 1, the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the series arm resonator closer to the input terminal 121 (first series arm resonator) may be smaller than the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the series arm resonator farther from the input terminal 121 (second series arm resonator).

[0195] The relative distances of the two series arm resonators with respect to the input terminal 121 are determined by the circuit configuration of the surface acoustic wave filter 100. Specifically, a series arm resonator farther from the input terminal 121 (e.g., the series arm resonator 104) is connected to the input terminal 121 via a series arm resonator closer to the input terminal 121 (e.g., the series arm resonator 101). Conversely, a series arm resonator closer to the input terminal 121 (e.g., the series arm resonator 101) is connected to the input terminal 121 without going through a series arm resonator farther from the input terminal 121 (e.g., the series arm resonator 104).

[0196] Similarly, when each of the two or more parallel arm resonators is a surface acoustic wave resonator 1, the number, shape, size, or any combination thereof of the multiple load members 51, 51A, 51B, 51C, or 51D may vary depending on the distance from the input terminal 121.

[0197] For example, when each of the two or more parallel arm resonators is a surface acoustic wave resonator 1, the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the parallel arm resonator closer to the input terminal 121 (first parallel arm resonator) may be smaller than the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the parallel arm resonator farther from the input terminal 121 (second parallel arm resonator).

[0198] The relative distances of the two parallel arm resonators with respect to the input terminal 121 are determined by the circuit configuration of the surface acoustic wave filter 100. Specifically, a node on a path (hereinafter referred to as a series path) connecting the input terminal 121 and the output terminal 122, to which a parallel arm resonator (e.g., the parallel arm resonator 114) farther from the input terminal 121 is connected, is connected to the input terminal 121 via a node on the series path to which a parallel arm resonator (e.g., the parallel arm resonator 111) closer to the input terminal 121 is connected. Conversely, a node on the series path to which a parallel arm resonator (e.g., the parallel arm resonator 111) closer to the input terminal 121 is connected is connected to the input terminal 121 without passing through a node on the series path to which a parallel arm resonator (e.g., the parallel arm resonator 114) farther from the input terminal 121 is connected.

[0199] It should be noted that a surface acoustic wave filter using the surface acoustic wave resonator 1 according to the first embodiment or its modification is not limited to the ladder-type surface acoustic wave filter 100. For example, the surface acoustic wave filter may include a longitudinally coupled surface acoustic wave resonator.

[0200] [2.2 Mounting Example of Surface Acoustic Wave Filter 100] Next, a mounting example of the surface acoustic wave filter 100 configured as above will be described with reference to Fig. 18. Fig. 18 is a plan view of the surface acoustic wave filter 100 according to this embodiment. In Fig. 18, hatching represents wiring.

[0201] 18 is one implementation example of the surface acoustic wave filter 100, and the surface acoustic wave filter 100 can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the surface acoustic wave filter 100 provided below should not be interpreted as limiting.

[0202] 18, the input terminal 121 is arranged in the upper left corner of the substrate 3, and the output terminal 122 is arranged in the lower right corner of the substrate 3. A plurality of ground terminals 123 are arranged discretely on the substrate 3. The plurality of series arm resonators 101 to 104 are arranged in order in the negative direction of the y-axis, and the plurality of parallel arm resonators 111 to 114 are arranged in order in the negative direction of the y-axis.

[0203] The plurality of series arm resonators 101 to 104 and / or the plurality of parallel arm resonators 111 to 114 including the surface acoustic wave resonator 1 according to the first embodiment or its modification may be determined according to the arrangement of the plurality of series arm resonators 101 to 104 and the plurality of parallel arm resonators 111 to 114 arranged in this manner on the substrate 3.

[0204] For example, the surface acoustic wave resonator 1 according to the first embodiment or its modification may be used for each of a plurality of resonators arranged side by side along the x-axis. In this case, in Fig. 18, the surface acoustic wave resonator 1 is used for each of the series arm resonator 102 and the parallel arm resonator 111, and the surface acoustic wave resonator 1 is used for each of the series arm resonator 103 and the parallel arm resonator 113.

[0205] [2.3 Summary] As described above, the surface acoustic wave filter 100 according to this preferred embodiment includes at least one series arm resonator 101 to 104 and at least one parallel arm resonator 111 to 114, and at least one of the at least one series arm resonator 101 to 104 and the at least one parallel arm resonator 111 to 114 is the surface acoustic wave resonator 1 according to the first preferred embodiment or its modification.

[0206] This allows the surface acoustic wave resonator 1 according to the first embodiment or its modification to be used in the ladder-type surface acoustic wave filter 100, thereby improving the characteristics of the surface acoustic wave filter 100 (for example, reducing loss and ripple).

[0207] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least one of the parallel arm resonators 111 to 114 may include the surface acoustic wave resonator 1, and at least one of the series arm resonators 101 to 104 may not include the surface acoustic wave resonator 1.

[0208] With this, since the surface acoustic wave resonator 1 is used for at least one of the parallel arm resonators 111 to 114, the Q value of at least one of the parallel arm resonators 111 to 114 can be improved, thereby improving the characteristics of the surface acoustic wave filter 100. Furthermore, since the surface acoustic wave resonator 1 is not used for at least one of the series arm resonators 101 to 104, it is possible to suppress a decrease in power durability and an increase in longitudinal mode ripples due to the multiple load members 51, 51A, 51B, 51C, or 51D. In particular, since the power durability of the series arm resonators becomes more severe than that of the parallel arm resonators when the passband shifts to the high frequency side with an increase in temperature, this has a significant effect in suppressing a decrease in power durability of at least one of the series arm resonators 101 to 104.

[0209] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least one of the series arm resonators 101 to 104 may include a surface acoustic wave resonator 1, and at least one of the parallel arm resonators 111 to 114 may include a surface acoustic wave resonator 1. In the surface acoustic wave resonator 1 included in at least one of the series arm resonators 101 to 104, the area of ​​a portion where the plurality of load members 51, 51A, 51B, 51C, or 51D overlap with the plurality of electrode fingers in a planar view of the substrate 3 may be smaller than the area of ​​a portion where the plurality of load members 51, 51A, 51B, 51C, or 51D overlap with the plurality of electrode fingers in a planar view of the substrate 3 in the surface acoustic wave resonator 1 included in at least one of the parallel arm resonators 111 to 114.

[0210] This makes it possible to suppress the longitudinal mode in the surface acoustic wave resonator 1 included in at least one of the series arm resonators 101 to 104, thereby suppressing ripples caused by the longitudinal mode, and improve the pass characteristics of the surface acoustic wave filter 100.

[0211] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least one of the series arm resonators 101 to 104 may include a surface acoustic wave resonator 1, and at least one of the parallel arm resonators 111 to 114 may include a surface acoustic wave resonator 1. The number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the surface acoustic wave resonator 1 included in at least one of the series arm resonators 101 to 104 may be smaller than the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the surface acoustic wave resonator 1 included in at least one of the parallel arm resonators 111 to 114.

[0212] This makes it possible to suppress the longitudinal mode in the surface acoustic wave resonator 1 included in at least one of the series arm resonators 101 to 104, thereby suppressing ripples caused by the longitudinal mode, and improve the pass characteristics of the surface acoustic wave filter 100.

[0213] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least one of the series arm resonators 101 to 104 may include a surface acoustic wave resonator 1, and at least one of the parallel arm resonators 111 to 114 may include a surface acoustic wave resonator 1, and the thickness of the plurality of load members 51, 51A, 51B, 51C, or 51D of the surface acoustic wave resonator 1 included in at least one of the series arm resonators 101 to 104 may be smaller than the thickness of the plurality of load members 51, 51A, 51B, 51C, or 51D of the surface acoustic wave resonator 1 included in at least one of the parallel arm resonators 111 to 114.

[0214] This makes it possible to suppress stop band ripples due to the surface acoustic wave resonator 1 included in at least one of the parallel arm resonators 111 to 114, thereby improving the pass characteristics of the surface acoustic wave filter 100.

[0215] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least one of the series arm resonators 101 to 104 may include a first series arm resonator 101 to 104 connected in series between the input terminal 121 and the output terminal 122 and a second series arm resonator 101 to 104 that is farther from the input terminal 121 than the first series arm resonators 101 to 104. Each of the first series arm resonators 101 to 104 and the second series arm resonators 101 to 104 may be a surface acoustic wave resonator 1, and the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the first series arm resonators 101 to 104 may be smaller than the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the second series arm resonators 101 to 104.

[0216] This makes it possible to suppress a decrease in the power durability of the series arm resonators closer to the input terminal 121, thereby improving the power durability of the surface acoustic wave filter 100. In particular, since higher power is applied to the resonators closer to the input terminal 121, the effect of improving the power durability of the surface acoustic wave filter 100 is significant.

[0217] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least one of the parallel arm resonators 111 to 114 may include a plurality of parallel arm resonators 111 to 114 connected in parallel between a path connecting the input terminal 121 and the output terminal 122 and ground, and the plurality of parallel arm resonators 111 to 114 may include a first parallel arm resonator 111 to 114 and a second parallel arm resonator 111 to 114 that is farther from the input terminal 121 than the first parallel arm resonators 111 to 114. Each of the first parallel arm resonators 111 to 114 and the second parallel arm resonators 111 to 114 may be a surface acoustic wave resonator 1, and the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the first parallel arm resonators 111 to 114 may be smaller than the number of electrode fingers overlapping with the plurality of load members 51, 51A, 51B, 51C, or 51D in the second parallel arm resonators 111 to 114.

[0218] This makes it possible to suppress a decrease in the power durability of the parallel arm resonators closer to the input terminal 121, thereby improving the power durability of the surface acoustic wave filter 100. In particular, since higher power is applied to the resonators closer to the input terminal 121, the effect of improving the power durability of the surface acoustic wave filter 100 is significant.

[0219] Furthermore, for example, in the surface acoustic wave filter 100 according to this embodiment, at least two of the at least one series arm resonator 101 to 104 and the at least one parallel arm resonator 111 to 114 may be the surface acoustic wave resonator 1, and may be arranged side by side along the x-axis on the substrate.

[0220] This allows the surface acoustic wave resonator 1 to be used for at least two resonators aligned in the propagation direction (x-axis direction) of the surface acoustic wave. In a surface acoustic wave resonator 1 including a plurality of load members 51, 51A, 51B, 51C, or 51D, the confinement effect of the surface acoustic wave can be improved by the plurality of load members 51, 51A, 51B, 51C, or 51D, and therefore the number of electrode fingers 421 of the reflecting electrode 42 can be reduced. This allows the size of the reflecting electrode 42 in the propagation direction to be reduced, and the packaging size of the surface acoustic wave resonator 1 to be reduced. In particular, for at least two resonators aligned in the propagation direction, the size in the propagation direction is large, and therefore the effect of reducing the packaging size of the surface acoustic wave resonator 1 is significant.

[0221] Third Embodiment Next, a third embodiment will be described. In this embodiment, a multiplexer using the surface acoustic wave filter 100 according to the second embodiment will be described with reference to FIG.

[0222] [3.1 Circuit Configuration of Multiplexer 200] Fig. 19 is a circuit configuration diagram of the multiplexer 200 according to this embodiment. Note that Fig. 19 is intended to illustrate a typical circuit configuration of the multiplexer 200, and the circuit configuration of the multiplexer 200 is not limited to the circuit configuration shown in Fig. 19. Therefore, the description of the multiplexer 200 provided below should not be construed in a limiting sense.

[0223] The multiplexer 200 includes transmit filters 201 and 203 and receive filters 202 and 204 .

[0224] The transmit filter 201 has a passband that includes the transmit band of band A, and can pass transmit signals of band A. The transmit filter 201 is connected between the antenna connection terminal 211 and the PA connection terminal 212.

[0225] The receive filter 202 has a passband that includes the receive band of band A, and can pass receive signals of band A. The receive filter 202 is connected between the antenna connection terminal 211 and the LNA connection terminal 213.

[0226] The transmit filter 203 has a passband that includes the transmit band of band B, and can pass the transmit signal of band B. The transmit filter 203 is connected between the antenna connection terminal 211 and the PA connection terminal 214. Note that the transmit filter 203 does not necessarily have to be included in the multiplexer 200.

[0227] The receive filter 204 has a passband that includes the receive band of band B and can pass receive signals of band B. The receive filter 204 is connected between the antenna connection terminal 211 and the LNA connection terminal 215. Note that the receive filter 204 does not necessarily have to be included in the multiplexer 200.

[0228] Each of bands A and B is a frequency band for a communication system built using a radio access technology (RAT), and is defined in advance by a standardization organization (e.g., 3GPP (registered trademark) (3rd Generation Partnership Project) and IEEE (Institute of Electrical and Electronics Engineers)). Examples of the communication system include a 5GNR (5th Generation New Radio) system, an LTE (Long Term Evolution) system, and a WLAN (Wireless Local Area Network) system.

[0229] The antenna connection terminal 211 is an external connection terminal connected to an antenna (ANT), and may be switchably connected to the antenna.

[0230] The PA connection terminal 212 is an external connection terminal connected to a power amplifier (PA). The PA connection terminal 212 may be switchably connected to the power amplifier.

[0231] The LNA connection terminal 213 is an external connection terminal connected to a low noise amplifier (LNA). The LNA connection terminal 213 may be switchably connected to the low noise amplifier.

[0232] The PA connection terminal 214 is an external connection terminal connected to a power amplifier (PA). The PA connection terminal 214 may be switchably connected to the power amplifier.

[0233] The LNA connection terminal 215 is an external connection terminal connected to a low noise amplifier (LNA). The LNA connection terminal 215 may be switchably connected to the low noise amplifier.

[0234] In this embodiment, at least one of the transmit filters 201 and 203 and the receive filters 202 and 204 included in the multiplexer 200 is the surface acoustic wave filter 100 according to the second embodiment.

[0235] For example, of the transmit filters 201 and 203 and the receive filters 202 and 204, only the receive filters 202 and / or 204 may be the surface acoustic wave filter 100. In other words, the receive filters 202 and / or 204 may be the surface acoustic wave filter 100 according to the second embodiment, and the transmit filters 201 and 203 do not have to be the surface acoustic wave filter 100.

[0236] Furthermore, for example, when the transmit filters 201 and / or 203 are the surface acoustic wave filters 100, the series arm resonator 104 that is closest to the antenna connection terminal 211 (output terminal 122) among the plurality of series arm resonators 101 to 104 may be the surface acoustic wave resonator 1 according to embodiment 1. Conversely, the series arm resonators 101 to 103 do not have to be the surface acoustic wave resonators 1.

[0237] Furthermore, for example, when the transmit filters 201 and / or 203 are the surface acoustic wave filters 100, the parallel arm resonator 114 that is closest to the antenna connection terminal 211 (output terminal 122) among the multiple parallel arm resonators 111 to 114 may be the surface acoustic wave resonator 1 according to embodiment 1. Conversely, the parallel arm resonators 111 to 113 do not have to be the surface acoustic wave resonators 1.

[0238] Furthermore, for example, when the receiving filters 202 and / or 204 are the surface acoustic wave filters 100, the series arm resonator 101, which is closest to the antenna connection terminal 211 (input terminal 121) among the plurality of series arm resonators 101 to 104, may be the surface acoustic wave resonator 1 according to embodiment 1. Conversely, the series arm resonators 102 to 104 do not have to be the surface acoustic wave resonators 1.

[0239] Furthermore, for example, when the receive filters 202 and / or 204 are the surface acoustic wave filters 100, the parallel arm resonator 111 that is closest to the antenna connection terminal 211 (input terminal 121) among the multiple parallel arm resonators 111 to 114 may be the surface acoustic wave resonator 1 according to embodiment 1. Conversely, the parallel arm resonators 112 to 114 do not have to be the surface acoustic wave resonators 1.

[0240] [3.2 Summary] As described above, the multiplexer 200 according to this embodiment includes the transmit filter 201 connected between the antenna connection terminal 211 and the PA connection terminal 212 and having a pass band that includes the transmit band of band A, and the receive filter 202 connected between the antenna connection terminal 211 and the LNA connection terminal 213 and having a pass band that includes the receive band of band A, and at least one of the transmit filter 201 and the receive filter 202 is the surface acoustic wave filter 100 described in embodiment 2.

[0241] This allows the surface acoustic wave filter 100 according to the second embodiment to be used in the multiplexer 200, thereby improving the characteristics of the multiplexer 200 (for example, reducing loss and ripple).

[0242] Furthermore, for example, in the multiplexer 200 according to this embodiment, the receiving filter 202 may be the surface acoustic wave filter 100, and the transmitting filter 201 may not be the surface acoustic wave filter 100.

[0243] This makes it possible to reduce signal loss and improve reception sensitivity by using the surface acoustic wave filter 100 for the receive filter 202. Furthermore, by not using the surface acoustic wave filter 100 for the transmit filter 201, it is possible to avoid a decrease in power durability due to the multiple load members 51, 51A, 51B, 51C, or 51D in the transmit filter 201, which requires higher power durability.

[0244] Furthermore, for example, in the multiplexer 200 according to this embodiment, the transmit filter 201 may be a surface acoustic wave filter 100 including a plurality of series arm resonators 101 to 104 connected in series between the antenna connection terminal 211 (output terminal 122) and the PA connection terminal 212 (input terminal 121), and the series arm resonator 104 that is closest to the antenna connection terminal 211 among the plurality of series arm resonators 101 to 104 may be the surface acoustic wave resonator 1 described in the first embodiment or its modification.

[0245] This makes it possible to improve the characteristics of the transmit filter 201 by using the surface acoustic wave resonator 1 described in the first embodiment or its modification as the series arm resonator 104 closest to the antenna connection terminal 211. In particular, by improving the Q value of the series arm resonator 104 closest to the antenna connection terminal 211 to which multiple filters (the transmit filter 201 and the receive filter 202) are connected, it is possible to effectively improve the characteristics of the transmit filter 201.

[0246] Furthermore, for example, in the multiplexer 200 according to this embodiment, the transmit filter 201 may be the surface acoustic wave filter 100 including a plurality of parallel arm resonators 111 to 114 connected in parallel between a path connecting the antenna connection terminal 211 (output terminal 122) and the PA connection terminal 212 (input terminal 121) and ground, and the parallel arm resonator 114, which is closest to the antenna connection terminal 211, among the plurality of parallel arm resonators 111 to 114, may be the surface acoustic wave resonator 1 described in the first embodiment or its modification.

[0247] This makes it possible to improve the characteristics of the transmit filter 201 by using the surface acoustic wave resonator 1 described in the first embodiment or its modification as the parallel arm resonator 114 closest to the antenna connection terminal 211. In particular, by improving the Q value of the parallel arm resonator 114 closest to the antenna connection terminal 211 to which multiple filters (the transmit filter 201 and the receive filter 202) are connected, it is possible to effectively improve the characteristics of the transmit filter 201.

[0248] Furthermore, for example, in the multiplexer 200 according to this embodiment, the receive filter 202 may be a surface acoustic wave filter 100 including a plurality of series arm resonators 101 to 104 connected in series between the antenna connection terminal 211 (input terminal 121) and the LNA connection terminal 213 (output terminal 122), and the series arm resonator 101, which is closest to the antenna connection terminal 211 among the plurality of series arm resonators 101 to 104, may be the surface acoustic wave resonator 1 described in the first embodiment or its modification.

[0249] This makes it possible to improve the characteristics of the receive filter 202 by using the surface acoustic wave resonator 1 described in the first embodiment or its modification as the series arm resonator 101 closest to the antenna connection terminal 211. In particular, by improving the Q value of the series arm resonator 101 closest to the antenna connection terminal 211 to which multiple filters (receive filter 202 and receive filter 202) are connected, it is possible to effectively improve the characteristics of the receive filter 202.

[0250] Furthermore, for example, in the multiplexer 200 according to this embodiment, the receive filter 202 may be the surface acoustic wave filter 100 including a plurality of parallel arm resonators 111 to 114 connected in parallel between a path connecting the antenna connection terminal 211 (input terminal 121) and the LNA connection terminal 213 (output terminal 122) and ground, and the parallel arm resonator 111, which is closest to the antenna connection terminal 211 among the plurality of parallel arm resonators 111 to 114, may be the surface acoustic wave resonator 1 described in the first embodiment or its modification.

[0251] This makes it possible to improve the characteristics of the receive filter 202 by using the surface acoustic wave resonator 1 described in the first embodiment or its modification as the parallel arm resonator 111 closest to the antenna connection terminal 211. In particular, by improving the Q value of the parallel arm resonator 111 closest to the antenna connection terminal 211 to which multiple filters (the transmit filter 201 and the receive filter 202) are connected, it is possible to effectively improve the characteristics of the receive filter 202.

[0252] Other Embodiments While the surface acoustic wave resonator, surface acoustic wave filter, and multiplexer according to one aspect of the present invention have been described above based on the embodiments, the surface acoustic wave resonator, surface acoustic wave filter, and multiplexer according to the present invention are not limited to the above embodiments. The present invention also includes other embodiments realized by combining any of the components in the above embodiments, modifications obtained by applying various modifications to the above embodiments that would occur to those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the above high-frequency circuits.

[0253] For example, in the circuit configurations of the surface acoustic wave filters and multiplexers according to the above-described embodiments, other circuit elements, wiring, etc. may be inserted between the paths connecting the circuit elements and signal paths shown in the drawings. For example, in the surface acoustic wave filter 100 of Fig. 15, inductors and / or capacitors may be connected in series and / or in parallel to any of the series arm resonators 101 to 104 and the parallel arm resonators 111 to 114.

[0254] Furthermore, for example, although the surface acoustic wave resonator 1 according to each of the above embodiments is a single-mode surface acoustic wave resonator, the present invention is not limited to this. For example, the surface acoustic wave resonator 1 may be a longitudinally coupled double-mode surface acoustic wave resonator. Even in this case, the same effects as those of a single-mode surface acoustic wave resonator can be obtained.

[0255] In the above-described embodiments, the electrode fingers included in the IDT electrode and the reflective electrode have a linear shape in a planar view. However, this is not limiting. For example, the electrode fingers included in the IDT electrode and / or the reflective electrode may have at least a partial curved shape in a planar view. In this case, the resonant frequencies or the anti-resonant frequencies may be substantially the same within the intersection region of the electrode fingers. Specifically, the IDT electrode and / or the reflective electrode may include the electrode fingers described in Patent Document 2 (WO 2024 / 009660) or Patent Document 3 (WO 2024 / 135259).

[0256] The features of the surface acoustic wave resonator, the surface acoustic wave filter, and the multiplexer described based on the above embodiments will be described below.

[0257] <1> A piezoelectric element comprising: a substrate including a piezoelectric layer; at least one electrode disposed on the substrate and including an IDT electrode; and a plurality of first load members disposed spaced apart on or within the substrate and made of a dielectric, wherein the at least one electrode includes a plurality of electrode fingers aligned along a first axis on the substrate, the plurality of electrode fingers extending along a second axis perpendicular to the first axis, each of the plurality of first load members at least partially overlapping with at least one corresponding electrode finger in a plan view of the substrate, wherein the number of electrode fingers arranged in a first sub-region that overlap with the plurality of first load members and the number of electrode fingers arranged in a third sub-region that overlap with the plurality of first load members are each greater than the number of electrode fingers arranged in a second sub-region that overlap with the plurality of first load members, the first sub-region, the second sub-region, and the third sub-region are obtained by equally dividing an area on the substrate in which the plurality of electrode fingers are arranged in the direction of the second axis, and the second sub-region is located between the first sub-region and the third sub-region, the plurality of first load members include two or more first load members overlapping with the electrode fingers arranged in the first sub-region, and two or more first load members overlapping with the electrode fingers arranged in the third sub-region.

[0258] <2> The surface acoustic wave resonator according to <1>, wherein the at least one electrode further includes a pair of reflective electrodes, and the IDT electrode is disposed between the pair of reflective electrodes.

[0259] <3> The surface acoustic wave resonator according to <2>, wherein at least one of the plurality of first load members at least partially overlaps with at least one corresponding electrode finger of the IDT electrode in a planar view of the substrate, and at least one other of the plurality of first load members at least partially overlaps with at least one corresponding electrode finger of the reflective electrode in a planar view of the substrate.

[0260] <4> The surface acoustic wave resonator according to any one of <1> to <3>, wherein the plurality of first load members correspond one-to-one to some of the plurality of electrode fingers.

[0261] <5> The surface acoustic wave resonator according to <4>, wherein each of the plurality of first load members overlaps a portion of a corresponding electrode finger in a plan view of the substrate.

[0262] <6> The surface acoustic wave resonator according to <5>, wherein a midpoint of the length of each of the plurality of first load members along the first axis is shifted toward a center of the IDT electrode along the first axis with respect to a midpoint of the length of the corresponding one of the electrode fingers along the first axis.

[0263] <7> The surface acoustic wave resonator according to any one of <1> to <6>, wherein the plurality of first load members are a plurality of first load films arranged on the substrate, and the plurality of first load films at least partially cover some of the plurality of electrode fingers.

[0264] <8> The surface acoustic wave resonator according to <7>, wherein in each of the plurality of first load films, a thickness of the first load film on a top surface of at least one corresponding electrode finger is greater than a thickness of the first load film on a side surface of the at least one corresponding electrode finger.

[0265] <9> The surface acoustic wave resonator according to <7> or <8>, further comprising: a protective film disposed on the substrate, the protective film covering the substrate and at least a portion of the plurality of electrode fingers.

[0266] <10> The surface acoustic wave resonator according to <9>, wherein the protective film is stacked on the plurality of first load films.

[0267] <11> The surface acoustic wave resonator according to <9> or <10>, wherein the plurality of first load films are made of a material different from that of the protective film.

[0268] <12> The surface acoustic wave resonator according to <11>, wherein the plurality of first load films are made of tantalum pentoxide, niobium pentoxide, tungsten (VI) oxide, silicon nitride, titanium (IV) oxide, cerium (IV) oxide, hafnium (IV) oxide, or ytterbium (III) oxide, and the material of the protective film is made of silicon dioxide or silicon nitride.

[0269] <13> The surface acoustic wave resonator according to any one of <1> to <6>, wherein the plurality of first load members are disposed within the substrate.

[0270] <14> The surface acoustic wave resonator according to <13>, wherein the substrate further includes a low acoustic velocity layer in which a bulk wave propagates at a speed slower than a speed of sound of an elastic wave propagating through the piezoelectric layer, the piezoelectric layer is disposed on the low acoustic velocity layer, and the plurality of first load members are disposed within the low acoustic velocity layer.

[0271] <15> The surface acoustic wave resonator according to any one of <1> to <14>, wherein a distance between an electrode finger overlapping the plurality of first load members and an electrode finger adjacent to the electrode finger but not overlapping the plurality of first load members is different from a distance between two adjacent electrode fingers overlapping the plurality of first load members or a distance between two adjacent electrode fingers not overlapping the plurality of first load members.

[0272] <16> The surface acoustic wave resonator according to any one of <1> to <15>, wherein a duty ratio of two or more electrode fingers overlapping the plurality of first load members is different from a duty ratio of two or more electrode fingers not overlapping any of the plurality of first load members.

[0273] <17> The surface acoustic wave resonator according to any one of <1> to <16>, further comprising a plurality of second load members that at least partially overlap tips of electrode fingers of the IDT electrode among the plurality of electrode fingers in a plan view of the substrate.

[0274] <18> The surface acoustic wave resonator according to <17>, wherein the plurality of first load members are a plurality of first load films arranged on the substrate, and the plurality of second load members are a plurality of second load films made of the same material as the plurality of first load films and arranged on the substrate.

[0275] <19> The surface acoustic wave resonator according to <18>, wherein the thicknesses of the plurality of first load films are the same as the thicknesses of the plurality of second load films.

[0276] <20> The surface acoustic wave resonator according to <18>, wherein the thicknesses of the plurality of first load films are greater than the thicknesses of the plurality of second load films.

[0277] <21> A surface acoustic wave filter comprising: at least one series arm resonator; and at least one parallel arm resonator, wherein at least one of the at least one series arm resonator and the at least one parallel arm resonator is the surface acoustic wave resonator according to any one of <1> to <20>.

[0278] <22> The surface acoustic wave filter according to <21>, wherein the at least one parallel arm resonator includes the surface acoustic wave resonator, and the at least one series arm resonator does not include the surface acoustic wave resonator.

[0279] <23> The surface acoustic wave filter according to <21>, wherein the at least one series arm resonator includes the surface acoustic wave resonator, the at least one parallel arm resonator includes the surface acoustic wave resonator, and an area of ​​a portion where the plurality of load members overlap with the plurality of electrode fingers in a planar view of the substrate, in the surface acoustic wave resonator included in the at least one series arm resonator, is smaller than an area of ​​a portion where the plurality of load members overlap with the plurality of electrode fingers in a planar view of the substrate, in the surface acoustic wave resonator included in the at least one parallel arm resonator.

[0280] <24> The surface acoustic wave filter according to <21>, wherein the at least one series arm resonator includes the surface acoustic wave resonator, the at least one parallel arm resonator includes the surface acoustic wave resonator, and the number of electrode fingers overlapping with the plurality of load members in the surface acoustic wave resonator included in the at least one series arm resonator is smaller than the number of electrode fingers overlapping with the plurality of load members in the surface acoustic wave resonator included in the at least one parallel arm resonator.

[0281] <25> The surface acoustic wave filter according to <21>, wherein the at least one series arm resonator includes the surface acoustic wave resonator, the at least one parallel arm resonator includes the surface acoustic wave resonator, and thicknesses of the plurality of load members of the surface acoustic wave resonator included in the at least one series arm resonator are smaller than thicknesses of the plurality of load members of the surface acoustic wave resonator included in the at least one parallel arm resonator.

[0282] <26> The surface acoustic wave filter according to <21>, wherein the at least one series arm resonator includes a first series arm resonator connected in series between an input terminal and an output terminal and a second series arm resonator farther from the input terminal than the first series arm resonator, each of the first series arm resonator and the second series arm resonator being the surface acoustic wave resonator, and the number of electrode fingers overlapping with the plurality of load members in the first series arm resonator is smaller than the number of electrode fingers overlapping with the plurality of load members in the second series arm resonator.

[0283] <27> The surface acoustic wave filter according to <21>, wherein the at least one parallel arm resonator includes a plurality of parallel arm resonators connected in parallel between a path connecting an input terminal and an output terminal and ground, the plurality of parallel arm resonators include a first parallel arm resonator and a second parallel arm resonator that is farther from the input terminal than the first parallel arm resonator, each of the first parallel arm resonator and the second parallel arm resonator is the surface acoustic wave resonator, and the number of electrode fingers overlapping with the plurality of load members in the first parallel arm resonator is smaller than the number of electrode fingers overlapping with the plurality of load members in the second parallel arm resonator.

[0284] <28> The surface acoustic wave filter according to <21>, wherein at least two of the at least one series arm resonator and the at least one parallel arm resonator are the surface acoustic wave resonators and are arranged side by side along the first axis on the substrate.

[0285] <29> A multiplexer comprising: a transmit filter connected between an antenna connection terminal and a PA connection terminal, the transmit filter having a passband including a predetermined transmit band; and a receive filter connected between the antenna connection terminal and an LNA connection terminal, the receive filter having a passband including the predetermined receive band, wherein at least one of the transmit filter and the receive filter is a surface acoustic wave filter according to any one of <21> to <28>.

[0286] <30> The multiplexer according to <29>, wherein the receiving filter is the surface acoustic wave filter, and the transmitting filter is not the surface acoustic wave filter.

[0287] <31> The multiplexer according to <29>, wherein the transmit filter is the surface acoustic wave filter, the at least one series arm resonator includes a plurality of series arm resonators connected in series between the antenna connection terminal and the PA connection terminal, and the series arm resonator closest to the antenna connection terminal among the plurality of series arm resonators is the surface acoustic wave resonator.

[0288] <32> The multiplexer according to <29>, wherein the transmit filter is the surface acoustic wave filter, the at least one parallel arm resonator includes a plurality of parallel arm resonators connected in parallel between a path connecting the antenna connection terminal and the PA connection terminal and ground, and the parallel arm resonator closest to the antenna connection terminal among the plurality of parallel arm resonators is the surface acoustic wave resonator.

[0289] <33> The multiplexer according to <29>, wherein the receiving filter is the surface acoustic wave filter, the at least one series arm resonator includes a plurality of series arm resonators connected in series between the antenna connection terminal and the LNA connection terminal, and the series arm resonator closest to the antenna connection terminal among the plurality of series arm resonators is the surface acoustic wave resonator.

[0290] <34> The multiplexer according to <29>, wherein the receiving filter is the surface acoustic wave filter, the at least one parallel arm resonator includes a plurality of parallel arm resonators connected in parallel between a path connecting the antenna connection terminal and the LNA connection terminal and ground, and the parallel arm resonator closest to the antenna connection terminal among the plurality of parallel arm resonators is the surface acoustic wave resonator.

[0291] <35> A surface acoustic wave resonator comprising: a substrate including a piezoelectric layer; at least one electrode disposed on the substrate and including an IDT electrode; and a dielectric film disposed on the at least one electrode, wherein the at least one electrode includes a plurality of electrode fingers arranged along a first axis on the substrate, the plurality of electrode fingers each extending along a second axis perpendicular to the first axis; an average thickness of the dielectric film on the electrode fingers disposed in a first sub-region and an average thickness of the dielectric film on the electrode fingers disposed in a third sub-region are each greater than an average thickness of the dielectric film on the electrode fingers disposed in a second sub-region; the first sub-region, the second sub-region, and the third sub-region are obtained by equally dividing an area on the substrate in which the plurality of electrode fingers are disposed in the direction of the second axis; and the second sub-region is located between the first sub-region and the third sub-region.

[0292] The present invention can be widely used as a surface acoustic wave device in communication devices such as mobile phones.

[0293] REFERENCE SIGNS LIST 1 Surface acoustic wave resonator 3 Substrate 3a, 31a, 31b Main surface 3b Electrode finger region 3b1 First sub-region 3b2 Second sub-region 3b3 Third sub-region 4, 4C, 6 Electrode 5, 5A Dielectric film 31 Piezoelectric layer 32 Low acoustic velocity layer 33 High acoustic velocity layer 34 Support substrate 41, 61 IDT electrode 42, 62 Reflection electrode 51, 51A, 51B, 51C, 51D, 53a, 53b, 71 Load member 52 Protective film 100 Surface acoustic wave filter 101, 102, 103, 104 Series arm resonator 111, 112, 113, 114 Parallel arm resonator 121 Input terminal 122 Output terminal 123 Ground terminal 200 Multiplexer 201, 203 Transmitting filter 202, 204 Receiving filter 211 Antenna connection terminal 212, 214 PA connection terminal 213, 215 LNA connection terminal 411a, 411b, 421, 611a, 611b, 621 Electrode fingers 412a, 412b, 422a, 422b, 612a, 612b, 622a, 622b Bus bar electrodes

Claims

1. A piezoelectric element comprising: a substrate including a piezoelectric layer; at least one first electrode disposed on the substrate, the first electrode including a first IDT electrode; and a plurality of first load members disposed on or within the substrate and spaced apart from one another and made of a dielectric, wherein the at least one first electrode includes a plurality of first electrode fingers aligned along a first axis on the substrate, the plurality of first electrode fingers each extending along a second axis perpendicular to the first axis, each of the plurality of first load members at least partially overlapping with at least one corresponding first electrode finger in a plan view of the substrate, the number of first electrode fingers among the first electrode fingers disposed in a first sub-region that overlap with the plurality of first load members and the number of first electrode fingers among the first electrode fingers disposed in a third sub-region that overlap with the plurality of first load members are greater than the number of first electrode fingers among the first electrode fingers disposed in a second sub-region that overlap with the plurality of first load members, a surface acoustic wave resonator, wherein the first subregion, the second subregion, and the third subregion are obtained by equally dividing a region on the substrate in which the plurality of first electrode fingers are arranged in the direction of the second axis, the second subregion is located between the first subregion and the third subregion, and the plurality of first load members include two or more first load members overlapping with the first electrode fingers arranged in the first subregion and two or more first load members overlapping with the first electrode fingers arranged in the third subregion.

2. The surface acoustic wave resonator according to claim 1, wherein the at least one first electrode further includes a pair of first reflecting electrodes, and the first IDT electrode is disposed between the pair of first reflecting electrodes.

3. A surface acoustic wave resonator as described in claim 2, wherein at least one of the plurality of first load members at least partially overlaps with at least one corresponding first electrode finger of the first IDT electrode in a planar view of the substrate, and at least one other of the plurality of first load members at least partially overlaps with at least one corresponding first electrode finger of the first reflecting electrode in a planar view of the substrate.

4. The surface acoustic wave resonator according to claim 1, wherein the plurality of first load members correspond one-to-one to some of the plurality of first electrode fingers.

5. The surface acoustic wave resonator according to claim 4, wherein each of the plurality of first load members overlaps a portion of a corresponding one of the first electrode fingers in a plan view of the substrate.

6. A surface acoustic wave resonator according to claim 5, wherein a midpoint of the length along the first axis of each of the plurality of first load members is shifted toward the center of the first IDT electrode along the first axis with respect to a midpoint of the length along the first axis of the corresponding one of the first electrode fingers.

7. A surface acoustic wave resonator according to any one of claims 1 to 6, wherein the plurality of first load members are a plurality of first load films arranged on the substrate, and the plurality of first load films at least partially cover some of the plurality of first electrode fingers.

8. The surface acoustic wave resonator according to claim 7, wherein in each of the plurality of first load films, the thickness of the first load film on a top surface of the corresponding at least one first electrode finger is greater than the thickness of the first load film on a side surface of the corresponding at least one first electrode finger.

9. The surface acoustic wave resonator according to claim 7 or 8, further comprising a protective film disposed on the substrate and covering the substrate and at least a portion of the plurality of first electrode fingers.

10. The surface acoustic wave resonator according to claim 9, wherein the protective film is stacked on the plurality of first load films.

11. The surface acoustic wave resonator according to claim 9 or 10, wherein the plurality of first load films are made of a material different from that of the protective film.

12. The surface acoustic wave resonator according to claim 11, wherein the plurality of first load films are made of tantalum pentoxide, niobium pentoxide, tungsten (VI) oxide, silicon nitride, titanium (IV) oxide, cerium (IV) oxide, hafnium (IV) oxide, or ytterbium (III) oxide, and the material of the protective film is silicon dioxide or silicon nitride.

13. The surface acoustic wave resonator according to any one of claims 1 to 6, wherein the plurality of first load members are disposed within the substrate.

14. A surface acoustic wave resonator as described in claim 13, wherein the substrate further includes a low acoustic velocity layer in which the acoustic velocity of a bulk wave propagating through the piezoelectric layer is slower than the acoustic velocity of an elastic wave propagating through the piezoelectric layer, the piezoelectric layer is disposed on the low acoustic velocity layer, and the plurality of first load members are disposed within the low acoustic velocity layer.

15. A surface acoustic wave resonator according to any one of claims 1 to 14, wherein a distance between a first electrode finger overlapping the multiple first load members and a first electrode finger adjacent to the first electrode finger but not overlapping the multiple first load members is different from a distance between two adjacent first electrode fingers that overlap the multiple first load members, or a distance between two adjacent first electrode fingers that do not overlap the multiple first load members.

16. A surface acoustic wave resonator according to any one of claims 1 to 15, wherein a duty ratio of two or more first electrode fingers overlapping the plurality of first load members is different from a duty ratio of two or more first electrode fingers that do not overlap any of the plurality of first load members.

17. A surface acoustic wave resonator according to any one of claims 1 to 16, wherein the pitch of two or more first electrode fingers overlapping the plurality of first load members is different from the pitch of two or more first electrode fingers that do not overlap any of the plurality of first load members.

18. A surface acoustic wave resonator according to any one of claims 1 to 17, wherein a width of at least one of the two or more first electrode fingers that does not overlap any of the multiple first load members is different from a width of at least one other of the two or more first electrode fingers that does not overlap any of the multiple first load members.

19. A surface acoustic wave resonator according to any one of claims 1 to 18, wherein the spacing between adjacent first electrode fingers of at least one set of the two or more first electrode fingers that do not overlap any of the multiple first load members is different from the spacing between adjacent first electrode fingers of at least another set of the two or more first electrode fingers that do not overlap any of the multiple first load members.

20. The surface acoustic wave resonator according to claim 19, wherein the intervals between adjacent first electrode fingers in a plurality of sets of the two or more first electrode fingers that do not overlap any of the plurality of first load members are different from each other.

21. The surface acoustic wave resonator according to any one of claims 1 to 20, further comprising a plurality of second load members that at least partially overlap tips of first electrode fingers of the first IDT electrode among the plurality of first electrode fingers in a plan view of the substrate.

22. A surface acoustic wave resonator as described in claim 21, wherein the plurality of first load members are a plurality of first load films arranged on the substrate, and the plurality of second load members are a plurality of second load films made of the same material as the plurality of first load films and arranged on the substrate.

23. The surface acoustic wave resonator according to claim 22, wherein the thicknesses of the plurality of first load films are the same as the thicknesses of the plurality of second load films.

24. The surface acoustic wave resonator according to claim 22, wherein the thicknesses of the plurality of first load films are greater than the thicknesses of the plurality of second load films.

25. A surface acoustic wave resonator according to any one of claims 1 to 24, wherein the piezoelectric layer includes a first principal surface and a second principal surface opposed to each other, the at least one first electrode being disposed on one of the first principal surface and the second principal surface, the surface acoustic wave resonator further including at least one second electrode including a second IDT electrode disposed on the other of the first principal surface and the second principal surface, the at least one second electrode including a plurality of second electrode fingers aligned along a first axis on the substrate, the plurality of second electrode fingers each extending along a second axis perpendicular to the first axis, and the plurality of second electrode fingers overlap one-to-one with the plurality of first electrode fingers in a planar view of the substrate.

26. The surface acoustic wave resonator according to claim 25, further comprising a plurality of third load members made of a dielectric and arranged spaced apart from one another on or within the substrate, each of the plurality of third load members at least partially overlapping at least one corresponding second electrode finger in a plan view of the substrate, the number of second electrode fingers among the second electrode fingers arranged in the first sub-region that overlap with the plurality of third load members and the number of second electrode fingers among the second electrode fingers arranged in the third sub-region that overlap with the plurality of third load members are each greater than the number of second electrode fingers among the second electrode fingers arranged in the second sub-region that overlap with the plurality of third load members, and the plurality of third load members include two or more third load members overlapping with the second electrode fingers arranged in the first sub-region and two or more third load members overlapping with the second electrode fingers arranged in the third sub-region.

27. The surface acoustic wave resonator according to claim 25 or 26, wherein the at least one second electrode further includes a pair of second reflecting electrodes, and the second IDT electrode is disposed between the pair of second reflecting electrodes.

28. A surface acoustic wave filter comprising: at least one series arm resonator; and at least one parallel arm resonator, wherein at least one of the at least one series arm resonator and the at least one parallel arm resonator is a surface acoustic wave resonator according to any one of claims 1 to 27.

29. The surface acoustic wave filter according to claim 28, wherein the at least one parallel arm resonator includes the surface acoustic wave resonator, and the at least one series arm resonator does not include the surface acoustic wave resonator.

30. The surface acoustic wave filter according to claim 28, wherein the at least one series arm resonator includes the surface acoustic wave resonator, the at least one parallel arm resonator includes the surface acoustic wave resonator, and an area of ​​a portion of the surface acoustic wave resonator included in the at least one series arm resonator where the multiple first load members overlap with the multiple electrode fingers in a planar view of the substrate is smaller than an area of ​​a portion of the surface acoustic wave resonator included in the at least one parallel arm resonator where the multiple first load members overlap with the multiple electrode fingers in a planar view of the substrate.

31. The surface acoustic wave filter according to claim 28, wherein the at least one series arm resonator includes the surface acoustic wave resonator, the at least one parallel arm resonator includes the surface acoustic wave resonator, and the number of electrode fingers overlapping with the multiple first load members in the surface acoustic wave resonator included in the at least one series arm resonator is smaller than the number of electrode fingers overlapping with the multiple first load members in the surface acoustic wave resonator included in the at least one parallel arm resonator.

32. The surface acoustic wave filter according to claim 28, wherein the at least one series arm resonator includes the surface acoustic wave resonator, the at least one parallel arm resonator includes the surface acoustic wave resonator, and a thickness of the plurality of first load members of the surface acoustic wave resonator included in the at least one series arm resonator is smaller than a thickness of the plurality of first load members of the surface acoustic wave resonator included in the at least one parallel arm resonator.

33. The surface acoustic wave filter according to claim 28, wherein the at least one series arm resonator includes a first series arm resonator connected in series between an input terminal and an output terminal and a second series arm resonator farther from the input terminal than the first series arm resonator, each of the first series arm resonator and the second series arm resonator being a surface acoustic wave resonator, and the number of electrode fingers overlapping the multiple first load members in the first series arm resonator is smaller than the number of electrode fingers overlapping the multiple first load members in the second series arm resonator.

34. The surface acoustic wave filter according to claim 28, wherein the at least one parallel arm resonator includes a plurality of parallel arm resonators connected in parallel between a path connecting an input terminal and an output terminal and ground, the plurality of parallel arm resonators including a first parallel arm resonator and a second parallel arm resonator farther from the input terminal than the first parallel arm resonator, each of the first parallel arm resonator and the second parallel arm resonator being the surface acoustic wave resonator, and the number of electrode fingers overlapping the plurality of first load members in the first parallel arm resonator is smaller than the number of electrode fingers overlapping the plurality of first load members in the second parallel arm resonator.

35. The surface acoustic wave filter according to claim 28, wherein at least two of the at least one series arm resonator and the at least one parallel arm resonator are surface acoustic wave resonators and are arranged side by side along the first axis on the substrate.

36. A multiplexer comprising: a transmit filter connected between an antenna connection terminal and a PA connection terminal, and having a passband including a transmission band of a predetermined band; and a receive filter connected between the antenna connection terminal and an LNA connection terminal, and having a passband including a reception band of the predetermined band, wherein at least one of the transmit filter and the receive filter is a surface acoustic wave filter as defined in any one of claims 28 to 35.

37. The multiplexer according to claim 36, wherein the receive filter is the surface acoustic wave filter, and the transmit filter is not the surface acoustic wave filter.

38. The multiplexer according to claim 36, wherein the transmit filter is the surface acoustic wave filter, the at least one series arm resonator includes a plurality of series arm resonators connected in series between the antenna connection terminal and the PA connection terminal, and the series arm resonator closest to the antenna connection terminal among the plurality of series arm resonators is the surface acoustic wave resonator.

39. The multiplexer according to claim 36, wherein the transmit filter is the surface acoustic wave filter, the at least one parallel arm resonator includes a plurality of parallel arm resonators connected in parallel between a path connecting the antenna connection terminal and the PA connection terminal and ground, and the parallel arm resonator closest to the antenna connection terminal among the plurality of parallel arm resonators is the surface acoustic wave resonator.

40. The multiplexer according to claim 36, wherein the receiving filter is the surface acoustic wave filter, the at least one series arm resonator includes a plurality of series arm resonators connected in series between the antenna connection terminal and the LNA connection terminal, and the series arm resonator closest to the antenna connection terminal among the plurality of series arm resonators is the surface acoustic wave resonator.

41. The multiplexer according to claim 36, wherein the receiving filter is the surface acoustic wave filter, the at least one parallel arm resonator includes a plurality of parallel arm resonators connected in parallel between a path connecting the antenna connection terminal and the LNA connection terminal and ground, and the parallel arm resonator closest to the antenna connection terminal among the plurality of parallel arm resonators is the surface acoustic wave resonator.

42. A surface acoustic wave resonator comprising: a substrate including a piezoelectric layer; at least one electrode including an IDT electrode disposed on the substrate; and a dielectric film disposed on the at least one electrode, wherein the at least one electrode includes a plurality of electrode fingers arranged along a first axis on the substrate, the plurality of electrode fingers each extending along a second axis perpendicular to the first axis, an average thickness of the dielectric film on the electrode fingers disposed in a first subregion and an average thickness of the dielectric film on the electrode fingers disposed in a third subregion are each greater than an average thickness of the dielectric film on the electrode fingers disposed in a second subregion, the first subregion, the second subregion and the third subregion are obtained by equally dividing an area on the substrate in which the plurality of electrode fingers are disposed in the direction of the second axis, and the second subregion is located between the first subregion and the third subregion.

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