Elastic wave apparatus, communication apparatus, and method for manufacturing an elastic wave apparatus

Abstract

It facilitates the improvement of specific characteristics. [Solution] The elastic wave device comprises a piezoelectric body having a first surface and an IDT electrode located on the first surface. The IDT electrode comprises a first busbar and a second busbar, a plurality of first electrode fingers extending from the first busbar toward the second busbar, and a plurality of second electrode fingers extending from the second busbar toward the first busbar. The intersection region of the first electrode fingers and the second electrode fingers comprises a central region located on the central side, a first edge region located toward the first busbar, and a second edge region located toward the second busbar. In the second edge region, the piezoelectric body has a recess between the first electrode finger and the second electrode finger. The thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region. Alternatively, the dimensions of the recess and the edge region satisfy predetermined conditions.

Description

Technical Field

[0005] ,

[0001] The present disclosure relates to an elastic wave device, a communication device including the elastic wave device, and a method for manufacturing an elastic wave device.

Background Art

[0002] An elastic wave device has, for example, a piezoelectric body and an IDT (Interdigital Transducer) electrode located on the upper surface of the piezoelectric body. The IDT electrode has a pair of bus bars facing each other and a plurality of electrode fingers extending in parallel from each of the pair of bus bars toward the other bus bar. Patent Document 1 proposes forming a recess in a region located around the tips of the plurality of electrode fingers on the upper surface of the piezoelectric body. The depth of the recess is less than 100 nm.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, an elastic wave device, a communication device, and a method for manufacturing an elastic wave device that are advantageous for improving specific characteristics are awaited.

Means for Solving the Problems

[0005] An elastic wave apparatus according to one aspect of the present disclosure comprises a piezoelectric body having a first surface and an IDT electrode located on the first surface, wherein the IDT electrode comprises a first busbar and a second busbar facing each other, a plurality of first electrode fingers extending in parallel from the first busbar to the second busbar, and a plurality of second electrode fingers extending in parallel from the second busbar to the first busbar and located between the plurality of first electrode fingers, wherein the intersection region where the first electrode fingers and the second electrode fingers overlap in the direction of elastic wave propagation comprises a central region located on the central side in the opposing direction of the first busbar and the second busbar, a first edge region located on the side of the first busbar, and a second edge region located on the side of the second busbar, wherein the piezoelectric body has a recess between the first electrode fingers and the second electrode fingers in the second edge region.

[0006] In the first respect, the thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region.

[0007] In the second aspect, when the repeating interval between the plurality of first electrode fingers and the plurality of second electrode fingers is p, the length of the portion of the recess located within the second edge region in the direction in which the first electrode fingers extend is L, and the depth of the recess is D, 0.50p ≤ L ≤ 2.50p, and 0.010p ≤ D ≤ 0.040p.

[0008] A communication device according to one aspect of the present disclosure includes an elastic wave device, an antenna connected to the elastic wave device, and an IC connected to the antenna via the elastic wave device.

[0009] A method for manufacturing the elastic wave apparatus according to one aspect of the present disclosure involves etching both the region of the first surface in which the recess is formed and the portion of the first electrode finger located in the second edge region. [Effects of the Invention]

[0010] According to the above configuration and / or procedure, for example, it becomes easier to improve specific characteristics. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic perspective view of an elastic wave apparatus according to an embodiment. [Figure 2] A schematic perspective view showing the elastic wave apparatus for the first example. [Figure 3] A schematic perspective view showing the elastic wave apparatus for the second example. [Figure 4] A schematic perspective view showing the elastic wave apparatus for the third example. [Figure 5] A schematic perspective view showing the elastic wave apparatus for the fourth example. [Figure 6] A schematic plan view showing another example of the planar shape of an electrode finger. [Figure 7] A schematic perspective view showing the tip and surrounding area of ​​the electrode finger. [Figure 8] A schematic cross-sectional view showing an example of electrode layer material. [Figure 9] A figure showing examples of the characteristics of elastic wave apparatuses according to the examples and comparative examples. [Figure 10] A diagram showing the characteristics of an embodiment in which the electrodes are not thinned. [Figure 11] This figure shows the characteristics of an example in which the electrode was thinned by an amount equal to 25% of the depth of the recess. [Figure 12] This figure shows the characteristics of an embodiment in which the electrode is thinned to 50% of the depth of the recess. [Figure 13] This figure shows the characteristics of an embodiment in which the electrode is thinned to 75% of the depth of the recess. [Figure 14] This figure shows the characteristics of an embodiment in which the electrode is thinned to 100% of the depth of the recess. [Figure 15] A schematic cross-sectional view showing a method for manufacturing an elastic wave apparatus according to an embodiment. [Figure 16] A schematic top view showing a filter according to this embodiment. [Figure 17] A block diagram showing a communication device according to an embodiment.

Best Mode for Carrying Out the Invention

[0012] In the drawings referred to below, for convenience, an orthogonal coordinate system D1D2D3 may be attached. The elastic wave device according to the embodiment may be used in any orientation, but for convenience, the +D3 side may be regarded as the upper side, and terms such as the upper surface and the lower surface may be used.

[0013] The drawings are schematic. Therefore, for example, the dimensional ratios on the drawings do not necessarily match the actual ones. Also, the dimensional ratios etc. may not match between the drawings. Specific shapes and / or dimensions etc. may be exaggerated or details may be omitted. However, the above does not deny that the actual shape and / or dimensions may be as shown in the drawings, or the shape and / or dimension features may be extracted from the drawings.

[0014] In the description of multiple aspects, basically, only the differences from the aspects described previously are stated. For matters not particularly mentioned, they may be the same as the configuration of the aspects described previously or may be inferred from the configuration of the aspects described previously. Also, for configurations corresponding or similar to each other in multiple aspects, even if there are differences, for convenience, they may be given the same reference numerals. After the description of multiple aspects, for convenience, the description may be made by referring only to the reference numerals of any one of the aspects. However, such description may be applied to other aspects as long as there is no contradiction etc. Multiple aspects may be appropriately combined as long as there is no contradiction etc.

[0015] (Outline of Elastic Wave Device) FIG. 1 is a schematic perspective view of an elastic wave device 1 according to an embodiment. The elastic wave device 1 has a piezoelectric substrate 3 and an electrode layer 5 located on its upper surface 7a (an example of the first surface).

[0016] At least a part of the region on at least the upper surface side of the piezoelectric substrate 3 is constituted by a piezoelectric body 7. In the illustrated example, the piezoelectric substrate 3 has, in order from above, a piezoelectric body 7, an intermediate layer 9, and a support substrate 11.

[0017] The electrode layer 5 has at least an IDT electrode 13. In the illustrated example, the entire electrode layer 5 is composed of the IDT electrode 13. The IDT electrode 13 has a pair of comb-shaped electrodes 15 (15A and 15B) arranged to interlock with each other. Each comb-shaped electrode 15 has a busbar 17 (17A or 17B) and a plurality of electrode fingers 19 (19A or 19B) extending in parallel from the busbar 17.

[0018] In this configuration, for example, when an electrical signal is input to the IDT electrode 13, an elastic wave is generated that propagates in the direction of the arrangement of the multiple electrode fingers 19 (D1 direction). The elastic wave device 1 functions as a resonator or filter, for example, by utilizing the resonance of the elastic wave.

[0019] Figure 2 shows a part of elastic wave apparatus 1A, which is a specific example (first example) of elastic wave apparatus 1, and corresponds to an enlarged view of region II in Figure 1. Note that although Figure 2 shows a portion related to some of the electrode fingers 19, the other portions related to the electrode fingers 19 can be considered basically the same. The various dimension lines shown in the upper right of Figure 2 indicate various regions. Note that the dimension lines are shown at the position of the upper surface of the electrode layer 5 in the D3 direction and may be located above the reference shape of the various regions. The same applies to Figures 3 to 5 described later.

[0020] The elastic wave device 1A has an intersection region RR where electrode fingers 19A and 19B overlap when viewed in the direction of elastic wave propagation (direction D1). The intersection region RR has a central region RC located on the central side in the opposing direction (direction D2) between busbars 17A and 17B, and edge regions RE (RE_A and RE_B) located on both sides of the central region RC.

[0021] The piezoelectric element 7 (upper surface 7a) has a recess 21 located between electrode fingers 19A and 19B in the edge region RE. The presence of the recess 21 causes the propagation speed of elastic waves in the edge region RE to be slower than that in the central region RC. As a result, for example, the use of the piston mode is facilitated.

[0022] Figure 3 shows a part of elastic wave apparatus 1B, which is another specific example (second example) of elastic wave apparatus 1, and corresponds to Figure 2. Elastic wave apparatus 1B differs from elastic wave apparatus 1A in that the thickness of the electrode finger 19 in the edge region RE is thinner than the thickness of the electrode finger 19 in the central region RC.

[0023] From the embodiments including the elastic wave devices 1A and 1B described above, various technical ideas can be extracted from different perspectives.

[0024] For example, from a first perspective, the thickness of the electrode fingers 19 in the edge region RE may be made relatively thin, as in the elastic wave apparatus 1B. This can improve certain characteristics, for example, as will be explained later with reference to Figures 10 to 14. Also, for example, as will be detailed later, the range of dimensions over which a certain value can be obtained for the above-mentioned specific characteristics is widened. Consequently, design and manufacturing are facilitated.

[0025] Here, when utilizing the piston mode by slowing the propagation speed of elastic waves in the edge region RE, the width of the electrode finger 19 in the edge region RE may be widened (see the right side of Figure 6 described later. This shape of the electrode finger 19 is sometimes referred to as the "hammer shape"). By widening the width, the mass of the electrode finger 19 in the edge region RE increases. On the other hand, in the elastic wave apparatus 1B, the mass of the electrode finger 19 decreases by making the electrode finger 19 thinner in the edge region RE. Therefore, a decrease in performance was expected in the elastic wave apparatus 1B. However, the opposite result was actually obtained as described above. As can be understood from this, the technical idea of ​​the first viewpoint is groundbreaking.

[0026] From a second perspective, the length L in the D2 direction of the edge region RE and the depth D of the recess 21 may be set as appropriate. For example, as shown in Figure 2, when the repeating interval of the electrode finger 19 is p, 0.50p ≤ L ≤ 2.50p, and It is acceptable that 0.010p ≤ D ≤ 0.040p. This makes it easier to obtain a certain level of value for specific characteristics, for example, as will be explained later with reference to Figures 10 to 14.

[0027] Furthermore, in viewpoints other than the first viewpoint (for example, the second viewpoint), the electrode finger 19 does not need to be relatively thin in the edge region RE (Figure 2). Also, in viewpoints other than the second viewpoint (for example, the first viewpoint), the length L and the depth D of the recess 21 are arbitrary. Moreover, the effects described above do not necessarily have to be achieved in any viewpoint.

[0028] The above is an overview of the embodiment. Below, we will provide a general explanation in the following order. 1. Elastic wave apparatus for the first example (Figures 1 and 2) 1.1. General Information on Elastic Wave Devices 1.2. Piezoelectric substrates and elastic waves 1.3. Electrode layer 1.4. Various regions and recesses 2. Elastic wave apparatus related to the second example (Figure 3) 3. Elastic wave apparatus related to the third example (Figure 4) 4. Elastic wave apparatus relating to the fourth example and other examples (Figure 5) 5. Other examples of recesses and electrode layers (Figures 6-8) 5.1. Other examples of planar shapes of electrode fingers 5.2. Inclination of various surfaces 5.3. Other examples of electrode layer materials 6. Examples (Figures 9-14) 6.1. Examples of characteristics of comparative examples and embodiments 6.2. Definition of FOM 6.3. Example of FOM calculation 7. Method for manufacturing an elastic wave apparatus (Figure 15) 8. Application Examples of Elastic Wave Devices 8.1. Filters (Figure 16) 8.2. Communication equipment (Figure 17) 9. Summary of Embodiments

[0029] (1. Elastic wave apparatus related to the first example) (1.1. General information on seismic wave equipment) The elastic wave device 1 illustrated in Figure 1 is configured as an end-face reflection type 1-port elastic wave resonator. In a 1-port elastic wave resonator, for example, an electrical signal input to one comb-tooth electrode 15 is output from the other comb-tooth electrode 15. In this process, the elastic wave device 1 performs conversion from electrical signals to elastic waves and from elastic waves to electrical signals. The elastic waves are reflected by a pair of (adjacent) end faces 7b located on both sides of the (one) IDT electrode 13 in the D1 direction and confined within the arrangement region of the IDT electrode 13. The end faces 7b are formed by the inner wall surface (the region composed of the piezoelectric material 7) of a groove 3a (recess) formed on the upper surface of the piezoelectric substrate 3.

[0030] Although not specifically shown in the figures, the electrode layer 5 may have a floating electrode between the IDT electrode 13 and the end face 7b that is not electrically connected to the IDT electrode 13. The end face 7b may be formed by the side surface of the piezoelectric body 7. The technology according to this disclosure is not limited to an end-face reflection type elastic wave resonator, and the structure that reflects elastic waves may be a reflector electrode instead of the end face 7b. The reflector electrode has, for example, a pair of busbars facing each other in the D2 direction and a plurality of reflector electrode fingers that are stretched across the pair of busbars and arranged in the D1 direction.

[0031] The elastic wave apparatus 1 may consist of resonators and / or filters other than a single-port elastic wave resonator. Examples of such configurations include, for example, a two-port elastic wave resonator and a multi-mode filter (including double-mode). In a two-port elastic wave resonator and a longitudinally coupled multi-mode filter, two or more IDT electrodes 13 are arranged in the D1 direction. Adjacent IDT electrodes 13 may be adjacent to each other without a reflective configuration (end face 7b in this embodiment). End faces 7b may be provided on both sides of the entire set of two or more IDT electrodes 13.

[0032] As previously described, the elastic wave apparatus 1 includes a piezoelectric substrate 3 and an electrode layer 5. Although not specifically shown in the figures, the elastic wave apparatus 1 may (or may not) have other appropriate components.

[0033] For example, the elastic wave apparatus 1 may have a protective film (not shown) that covers the upper surface 7a from above the electrode layer 5. Such a protective film is made of an insulating material such as SiO2 and contributes to reducing the likelihood of corrosion of the IDT electrode 13, etc., and / or compensating for changes in characteristics caused by temperature changes in the elastic wave apparatus 1. The protective film may cover the inner surfaces of the recesses 21 and / or grooves 3a. Alternatively, the protective film may not cover the inner surfaces of the recesses 21 and / or grooves 3a, leaving the inner surfaces of the recesses 21 and / or grooves 3a exposed.

[0034] Furthermore, for example, the elastic wave apparatus 1 may have an additional film that overlaps the upper or lower surface of the electrode layer 5 and has a shape that basically fits within the electrode layer 5 in a planar view. Such an additional film is made of an insulating material or metallic material that has different acoustic properties from the material of the electrode layer 5, and contributes to improving the reflection coefficient of elastic waves. However, the additional film (especially an additional film made of a conductor) may be considered as part of the electrode layer 5.

[0035] Furthermore, for example, the elastic wave apparatus 1 may have a relatively thin insulating film that overlaps the entire upper surface 7a and is interposed between the electrode layer 5 and the upper surface 7a. When the electrode layer 5 is located on the upper surface 7a in the elastic wave apparatus 1, such an embodiment may also be included in the elastic wave apparatus 1.

[0036] Furthermore, for example, the elastic wave device 1 may have a conductive layer and / or insulating layer that overlap the entire lower surface of the piezoelectric substrate 3. However, these may be considered as part of the piezoelectric substrate 3.

[0037] (1.2. Piezoelectric substrates and elastic waves) The piezoelectric substrate 3 is, for example, generally flat. The upper surface 7a (excluding the recess 21) is generally planar. The planar shape and dimensions (planar direction and thickness) of the piezoelectric substrate 3 are arbitrary. The piezoelectric substrate 3 illustrated in Figure 1 has a laminated structure including the piezoelectric element 7, as described above. The thickness of each layer is generally constant. The areas of multiple layers may be the same or different from each other. For example, the piezoelectric element 7 may or may not have the same area as the upper surface of the layer located below it (e.g., the support substrate 11).

[0038] The piezoelectric element 7 is made of, for example, a piezoelectric single crystal. The material constituting the single crystal is, for example, lithium tantalate (LiTaO3, sometimes referred to as "LT") or lithium niobate (LiNbO3, sometimes referred to as "LN"). The cut angle may be set appropriately depending on the type of elastic wave used. For example, the piezoelectric element 7 is of rotational Y-cut X propagation. That is, the X axis is parallel to the upper surface 7a (D1 axis) of the piezoelectric element 7, and the Y axis is inclined at a predetermined angle around the X axis with respect to the normal to the upper surface 7a (D3 axis) of the piezoelectric element 7. In the case of LT, for example, a 42°±10° Y-cut X propagation substrate may be used.

[0039] The thickness of the piezoelectric element 7 is arbitrary; for example, it may be 0.1p or more, 0.2p or more, or 0.3p or more, and it may also be 2.0p or less, 1.0p, or 0.5p or less, and the above lower and upper limits may be any combination. For clarification, the thickness of the piezoelectric element 7 may also be outside the above range (for example, greater than 2p).

[0040] The intermediate layer 9 contributes, for example, to adjusting the energy confinement of elastic waves and / or improving temperature characteristics. The intermediate layer 9 is located on the lower side (an example of the second surface) of the piezoelectric element 7. The intermediate layer 9 may be made of a material with lower acoustic impedance and / or sound velocity (both values, for example, when focusing on elastic waves or slow transverse waves of the intended mode; the same applies hereinafter) compared to the piezoelectric element 7. An example of such a material for the intermediate layer 9 is silicon dioxide (SiO2).

[0041] The thickness of the intermediate layer 9 is arbitrary; for example, it may be thinner than the piezoelectric element 7 (as shown in the illustration), the same thickness as the piezoelectric element 7, or thicker. Also, for example, the thickness of the intermediate layer 9 may be 0.05p or more, 0.10p or more, or 0.15p or more, and may be 1.0p or less, 0.5p or less, or 0.3p or less, and any combination of the above lower and upper limits may be used. For clarification, the thickness of the intermediate layer 9 may also be outside the above range (for example, greater than 1.0p).

[0042] The support substrate 11 may be made of a material with a sound velocity faster than the piezoelectric element 7 or the intermediate layer 9, and may contribute to confining the energy of the elastic waves in the piezoelectric element 7. The support substrate 11 may also contribute to ensuring the strength of the piezoelectric substrate 3, and / or contribute to compensating for changes in the characteristics of the elastic wave device 1 caused by temperature changes (temperature compensation). The material of the support substrate 11 is arbitrary. For example, when the support substrate 11 contributes to temperature compensation, examples of materials include silicon (Si), sapphire (single crystal of Al2O3), aluminum oxide sintered body, or quartz (SiO2). The thickness of the support substrate 11 is arbitrary; for example, it may be thicker than the thickness of the piezoelectric element 7, and may be between 100 μm and 300 μm.

[0043] Although not specifically shown in the illustrations, the piezoelectric substrate 3 may have the following configuration, contrary to the above description. The intermediate layer 9 is made of a material that has a higher acoustic impedance and / or sound velocity compared to the piezoelectric material 7. Examples of such materials include tantalum pentoxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), titanium oxide (TiO2), silicon nitride (SiNx), and aluminum nitride (AlN). • Instead of the intermediate layer 9, the device includes two or more layers of films made of two or more materials (including multilayer films). The multilayer film may be constructed by alternately stacking five or more layers of a material with an acoustic impedance lower than that of the piezoelectric element 7 and a layer of a material with an acoustic impedance higher than that of the piezoelectric element 7. Any of the materials may be those previously mentioned. Regarding the intermediate layer 9, it is not intended to have any active acoustic effect. For example, it is intended to bond the piezoelectric element 7 to the support substrate 11. - In this configuration, there is no intermediate layer 9, and the support substrate 11 is directly bonded to the lower surface of the piezoelectric element 7 (directly below the area where the IDT electrode 13 is placed). - An air layer is provided instead of the intermediate layer 9. For example, a recess is formed on the upper surface of the support substrate 11, and the piezoelectric element 7 is placed on the support substrate 11 so as to close the recess. • The entire piezoelectric substrate 3 is composed of a piezoelectric element 7. In this case, the thickness of the piezoelectric element 7 may be thicker than in other embodiments, for example, 10p or more.

[0044] The type of elastic wave used in the elastic wave apparatus 1 is arbitrary. For example, leaky waves, Rayleigh waves, Love waves, or plate waves may be used. In the simulation calculation described later, the cut-off angle of the piezoelectric element 7 is set to use leaky waves. Generally, in the elastic wave apparatus 1 that uses leaky waves, the cut-off angle and boundary conditions are set to minimize propagation attenuation. In such cases, leaky waves and Rayleigh waves exhibit similar behavior. Therefore, it is expected that the same results as in the simulation calculation described later will be obtained even when using Rayleigh waves.

[0045] As previously mentioned, the cut angle of the piezoelectric element 7 may be set appropriately depending on the type of elastic wave used. Typical examples of cut angles for rotational Y-cut X propagation using leaky waves include 36° for LT and 41° for LN. Furthermore, in the simulation calculations described later, rotational Y-cut X propagation of LT at 42° is used. Based on the analogy that LT and LN have the same crystal system, the cut angles at which the propagation loss of leaky waves is small are close. For these reasons, the cut angle of LT or LN may be, for example, 30° to 50°, 36° to 46°, or 41° to 43°, or an equivalent angle.

[0046] The elastic wave used here may be, for example, the component (principal component) that accounts for 50% or more or 80% or more of the energy of the elastic wave at the frequency of the principal resonance. The principal resonance may refer to, for example, the one with the smallest impedance minimum (or, from another perspective, impedance at the resonance frequency) among multiple resonances with different resonant frequencies that occur at the IDT electrode 13 (in other words, the resonator). In the description of the embodiments, unless otherwise specified, the resonant frequency (and anti-resonant frequency) refers to that of the principal resonance.

[0047] (1.3. Electrode layer) The electrode layer 5 is made of, for example, a metal. The specific type of metal is arbitrary and may be, for example, Al or an alloy with Al as the main component (Al alloy). An Al alloy is, for example, an Al-Cu alloy. The main component may be, for example, a component that accounts for 50% or more by mass or 80% or more by mass (the same applies to other alloys). The electrode layer 5 may be made up of multiple metal layers made of different materials stacked together.

[0048] In the first example, the thickness of the various parts of the electrode layer 5 (e.g., the busbar 17 and the electrode fingers 19) is the same. Furthermore, the specific value of the thickness of the electrode layer 5 is arbitrary. For example, the thickness (the thickness of the part that is not thinned in the second example, etc.) may be 0.14p or more or 0.16p or more, and may be 0.20p or less or 0.18p or less, and the above lower and upper limits may be any combination. And / or, the thickness of the electrode layer 5 may be 50nm or more and 600nm or less.

[0049] The busbar 17 is formed, for example, as a long, linear shape extending in the direction of elastic wave propagation (D1 direction) with a generally constant width. Unlike the illustrated example, the busbar 17 may have varying widths or be inclined with respect to the direction of elastic wave propagation. The busbar 17 may also have multiple openings arranged in one or more rows in the D1 direction.

[0050] The electrode fingers 19 are formed in a long, linear shape, for example, extending in a direction (D2 direction) roughly perpendicular to the propagation direction of the elastic wave. The lengths of the multiple electrode fingers 19 may be equal to each other (as shown in the example) or may be different (so-called apodizing may be applied). The width (D1 direction) of each electrode finger 19 may be constant (as shown in the example) or may vary depending on the position in the D2 direction.

[0051] The widths of the multiple electrode fingers 19 are, for example, the same. However, the widths of some or all of the multiple electrode fingers 19 may differ from each other. In the example in Figure 1, the widths of the electrode fingers 19 at both ends are approximately half the width of the other electrode fingers 19. This adjusts the phase between the incident wave and the reflected wave at the end face 7b. Conversely to the illustrated example, the width of the electrode fingers 19 at the ends may be wider.

[0052] The specific width of the electrode finger 19 is arbitrary. For example, the width of the electrode finger / p shall be referred to as the Duty. For most of the electrode fingers 19, excluding the unique electrode fingers 19 (e.g., the electrode fingers 19 at both ends), the Duty may be between 0.3 and 0.7. If the width of each electrode finger 19 differs depending on its position in the D2 direction, the above range may be applied, for example, to the width of the widest part or the average value of the widths.

[0053] The number of electrode fingers 19 is arbitrary. In Figure 1, for convenience, the number of electrode fingers 19 is shown as a small number. In reality, more electrode fingers 19 may be arranged than shown. For example, the number of electrode fingers 19 may be 50 or more, or 100 or more, or 400 or less, or 300 or less, and the above lower and upper limits may be combined in any way.

[0054] The pitch p described above can also be understood as the distance between the centers of two adjacent electrode fingers 19. The pitch p is basically constant within the IDT electrode 13. However, a portion of the IDT electrode 13 may be provided with a narrow-pitch section where the pitch p is narrower than the rest of the electrode, or a wide-pitch section where the pitch p is wider than the rest of the electrode. In addition, a portion of the IDT electrode 13 may have a sparsed section where the electrode fingers 19 are substantially sparsed.

[0055] In the description of the embodiments, when referring to pitch p, unless otherwise specified, it means the pitch of the portion excluding the special portions such as the narrow-pitch portion, wide-pitch portion, or thinned portion (most of the multiple electrode fingers 19). Furthermore, if the pitch changes even in the majority of the electrode fingers 19 excluding the special portions, the average value of the pitch of the majority of the electrode fingers 19 (for example, 80% of the total number of electrodes selected to minimize the pitch variance) may be used as the value of pitch p.

[0056] When a voltage is applied to a pair of comb-tooth electrodes 15, an electric field is applied to the piezoelectric body 7 by the multiple electrode fingers 19, causing the piezoelectric body 7 to vibrate. In other words, elastic waves are excited. Among elastic waves of various wavelengths that propagate in various directions, elastic waves that propagate in the direction of the arrangement of the multiple electrode fingers 19, with the pitch p of the multiple electrode fingers 19 being approximately half a wavelength (λ / 2), tend to have a large amplitude because multiple waves excited by the multiple electrode fingers 19 overlap in phase.

[0057] Furthermore, the elastic waves propagating through the piezoelectric element 7 are converted into electrical signals by the multiple electrode fingers 19. At this time, similar to when the elastic waves are excited, the intensity of the converted electrical signals tends to increase when the elastic waves propagate in the direction of the arrangement of the multiple electrode fingers 19, with the pitch p of the multiple electrode fingers 19 being approximately half a wavelength (λ / 2).

[0058] Due to the effects described above (and other effects not explained here), the elastic wave device 1 functions as a resonator whose resonant frequency is the frequency of an elastic wave with a pitch p of approximately half a wavelength (λ / 2). The frequency (or pitch p, from another perspective) targeted by the elastic wave device 1 is arbitrary. For example, the pitch p may be between 0.5 μm and 6 μm.

[0059] (1.4. Various regions and recesses) In the crossover region RR shown in Figure 2, electrode fingers 19A and 19B (which are adjacent to each other) overlap when viewed in the direction of elastic wave propagation (direction D1). The crossover region RR can also be considered as the region between an imaginary line connecting the tips of multiple electrode fingers 19A and an imaginary line connecting the tips of multiple electrode fingers 19B. In the illustrated example, the crossover region RR is rectangular. As previously described, the busbar 17 may be inclined in the direction D1, and the multiple electrode fingers 19 may be apodized. Therefore, the crossover region RR is not necessarily rectangular. However, for convenience in describing the embodiments, it may be assumed without further explanation that the crossover region RR (and other regions) is rectangular. The length of the crossover region RR in the D2 direction (crossover width) is arbitrary. For example, the crossover width (e.g., average value) may be between 20p and 150p.

[0060] The central region RC includes the central position of the intersecting region RR in the D2 direction. The recess 21 extends, for example, across the entire edge region RE in the D2 direction. Conversely, the boundary between the central region RC and the edge region RE may be the position of the end of the recess 21 on the central region RC side. The shapes of the central region RC and the edge region RE are, for example, rectangular. However, as can be understood from the above explanation, the shapes of the central region RC and / or the edge region RE do not have to be rectangular. The length of the central region RC in the D2 direction is, for example, longer than the sum of the lengths of the two edge regions RE in the D2 direction. The lengths of the two edge regions RE in the D2 direction are, for example, the same. Specific examples of the lengths of the edge regions RE in the D2 direction will be described later with reference to Figures 10 to 14.

[0061] The region between the busbars 17, outside the crossing region RR, is referred to as the gap region RG (RG_A and RG_B). The gap region RG includes the gap between the busbar 17 and the electrode finger 19. The shape of the gap region RG is, for example, rectangular. However, the shape of the gap region RG does not have to be rectangular. The length of the gap region RG in the D2 direction is arbitrary and may be, for example, 0.2p or more and 1p or less.

[0062] The recess 21 extends, for example, across adjacent edge regions RE and gap regions RG. The planar shape of the recess 21 is, for example, generally the same as (but may differ from) the shape of the non-placed regions of the electrode layer 5 in the edge region RE and gap region RG. In the illustrated example, the planar shape of the recess 21 is generally U-shaped, surrounding the tips of each electrode finger 19 (excluding the electrode fingers 19 on both sides in the D1 direction). Its contour line is, for example, generally composed of straight lines. The planar shapes (including dimensions) of the multiple recesses 21 are, for example, the same as (but may differ from) each other. The depth of each recess 21 is, for example, generally constant. The depths of the multiple recesses 21 are, for example, the same as each other.

[0063] (2. Elastic wave apparatus related to the second example) As previously described, the elastic wave apparatus 1B shown in Figure 3 differs from the elastic wave apparatus 1A in that the thickness of the electrode finger 19 in the edge region RE is relatively thinner. In addition, the thickness of the electrode finger 19 in the gap region RG is also thinner than the thickness in the central region RC. From another perspective, the electrode finger 19 is thinned in the D2 direction in the area where the recess 21 is formed.

[0064] More specifically, the electrode finger 19 has its tip portion located in the edge region RE, and this tip portion is relatively thin throughout its entire width. Furthermore, the electrode finger 19 has its base portion located in both the edge region RE and the gap region RG, and this base portion is also relatively thin throughout its entire width. In other words, the electrode finger 19 is thicker in the central portion compared to its end portions.

[0065] In the electrode layer 5, for example, the thicknesses of various parts that are relatively thicker (the central region RC and the busbar 17) are, for example, the same. Also, in the electrode layer 5, the thicknesses of various parts that are relatively thinner (the tip and base portions of the electrode finger 19) are, for example, the same. In other words, there are two types of thicknesses in the electrode layer 5. However, there may be three or more types of thicknesses. This is also true in the third example described later.

[0066] In the electrode finger 19, the difference dt (Figure 8) between the thickness in the central region RC and the thickness in the edge region RE is arbitrary. For example, the difference dt may be 1% or more, 5% or more, or 10% or more of the thickness in the central region RC, and may also be 90% or less, or 50% or less, and the above lower and upper limits may be any combination. Furthermore, the difference dt may be smaller than the depth D of the recess 21, equal to, or larger than. When the difference dt is smaller than the depth D of the recess 21, the difference between the two is arbitrary, and may be, for example, 1% or more, 5% or more, or 10% or more of the depth D of the recess 21.

[0067] (3. Elastic wave apparatus related to the third example) Figure 4 is a schematic perspective view of elastic wave apparatus 1C, which is another specific example (third example) of elastic wave apparatus 1, and corresponds to Figure 2. Elastic wave apparatus 1C differs from elastic wave apparatus 1B in that the thickness of at least the portion of the busbar 17 on the electrode finger 19 side is thinner than the thickness in the central region RC of the electrode finger 19.

[0068] More specifically, the busbar 17 is relatively thinned, for example, along its entire length on the edge side of the electrode finger 19. In another view, the busbar 17 is thinned in the D1 direction over the area where the multiple recesses 21 are located. The thinned portion may be part of the width of the busbar 17 (in the D2 direction) (as shown in the example) or the entire width. In the former case, the width of the thinned portion (in the D2 direction) is constant in the D1 direction (as shown in the example). However, the width of the thinned portion may vary depending on its position in the D1 direction. The specific size of the width of the thinned portion is arbitrary; for example, it may be less than half the width of the busbar 17, or more than half, and may be less than 1p or more than 1p.

[0069] (4. Elastic wave apparatus relating to the fourth example and other examples) Figure 5 is a schematic perspective view of elastic wave apparatus 1D, which is another specific example (fourth example) of elastic wave apparatus 1, and corresponds to Figure 2. Elastic wave apparatus 1D differs from elastic wave apparatus 1B in that the recess 21 is not located in the gap region RG, and the thickness of the electrode finger 19 in the gap region RG is not relatively thin.

[0070] More specifically, the recess 21 is located only in the edge region RE and does not surround the tip of the electrode finger 19, but is located to the side of the electrode finger 19. Its shape is, for example, roughly rectangular. Furthermore, the thickness of the electrode finger 19 in the gap region RG at the base is the same as the thickness of the portion in the central region RC. It can also be considered that, similar to the elastic wave device 1B, the electrode layer 5 (electrode finger 19) in the D2 direction is thinned only in the area where the recess 21 is formed.

[0071] The recess 21, located only in the edge region RE, may, for example, extend across the entire edge region RE in the D2 direction (as shown in the illustration), or it may be located only in a part of the central region RC side. Similarly, the relatively thin portion of the electrode finger 19 may extend across the entire edge region RE in the D2 direction (as shown in the illustration), or it may be located only in a part of the central region RC side. In other words, the tip of the electrode finger 19 may be relatively thicker.

[0072] Other specific examples: Although not specifically shown, the recess 21 may be intermediate in size between that in elastic wave devices 1A to 1C and that in elastic wave device 1D. That is, the recess 21 may be located in the edge region RE and in a part of the gap region RG on the edge region RE side. The planar shape of the recess 21 in elastic wave device 1D may be combined with the electrode layer 5 (electrode finger 19) of elastic wave device 1A, which has a constant thickness.

[0073] (5. Other examples of recesses and electrode layers) (5.1. Other examples of the planar shape of electrode fingers) Figure 6 is a plan view showing another example of the planar shape of electrode layer 5. These figures correspond to region II in Figure 1. For convenience, the electrode layers 5 shown in Figure 6 will be referred to as electrode layers 5E and 5F. Electrode layers 5E and 5F can be applied to any of the specific examples of the elastic wave apparatus 1 (e.g., elastic wave apparatuses 1A to 1D).

[0074] In electrode layer 5E, the electrode finger 19 has a narrower width in the edge region RE than in the central region RC. Furthermore, in the illustrated example, the electrode finger 19 also has a narrower width in the gap region RG than in the central region RC.

[0075] When the electrode layer 5E is applied to the elastic wave apparatus 1A to 1C, the width of the electrode finger 19 in the portion adjacent to the recess 21 in the D1 direction is narrower than the width of the portion not adjacent to the recess 21. Furthermore, when this configuration is applied to the elastic wave apparatus 1D, the width of the electrode finger 19 may be narrower only in the edge region RE than in the central region RC (the width in the gap region RG may be the same as in the central region RC).

[0076] In the electrode finger 19 of the electrode layer 5E, the difference in width between the relatively thin portion and the relatively thick portion is arbitrary. For example, the difference between the two may be 0.01 times or more, 0.05 times or more, or 0.10 times or more the width in the central region RC, or 0.50 times or less, 0.20 times or less, 0.10 times or less, or 0.05 times or less, and the above lower and upper limits may be combined in a way that does not cause contradiction.

[0077] In electrode layer 5F, unlike electrode layer 5E, the width of the electrode finger 19 in the edge region RE is wider than the width in the central region RC. The difference in width between the two in this case is also arbitrary. For example, the difference may be 0.05 times or more, or 0.1 times or more, the width in the central region RC. The upper limit of the difference between the two is arbitrary, as long as a short circuit does not occur between adjacent electrode fingers 19.

[0078] As shown by the dotted lines in electrode layers 5E and 5F, the IDT electrode 13 may have multiple dummy electrodes 23 (only one is shown in Figure 6 for convenience). The multiple dummy electrodes 23 protrude from the busbar 17 between the multiple electrode fingers 19 of each comb-tooth electrode 15 and face the tips of the multiple electrode fingers 19 of the other comb-tooth electrode 15 via a gap. However, the amount of protrusion of the dummy electrodes 23 from the busbar 17 may be relatively small. For example, the amount of protrusion may be 0.25p or less (or not).

[0079] Even when a dummy electrode 23 is provided, in the description of the embodiment, the gap region RG is assumed to be the region between the crossing region RR and the busbar 17. Within the gap region RG, the area where the dummy electrode 23 is located in the D2 direction is referred to as the dummy region (reference numeral omitted), and the area where the gap between the tip of the electrode finger 19 and the dummy electrode 23 is located is referred to as the inter-tip region (reference numeral omitted).

[0080] When dummy electrodes 23 are applied to elastic wave devices 1A to 1C, the shape of the recess 21 may be, for example, roughly H-shaped. Also, when the recess 21 has a shape intermediate between elastic wave devices 1A to 1C and elastic wave device 1D, it may be located in part or all of the intersection region RR on the tip-to-tip region, or it may be located in all of the tip-to-tip region and part of the tip-to-tip region on the dummy region side.

[0081] The thickness of the dummy electrode 23 is arbitrary. For example, in elastic wave apparatus 1A, the thickness of the dummy electrode 23 may be the same as the thickness of the electrode finger 19. In elastic wave apparatuses 1B and 1C, the thickness of the dummy electrode 23 may be the same as the thickness of the electrode finger 19 in the edge region RE. In other words, for example, the portion of the dummy electrode 23 adjacent to the recess 21 in the D1 direction may be relatively thin. In elastic wave apparatus 1D, the thickness of the dummy electrode 23 may be the same as the thickness of the electrode finger 19 in the central region RC.

[0082] (5.2. Inclination of various surfaces) Figure 7 (mostly) is a perspective view showing an enlarged view of the tip portion of the electrode finger 19, corresponding to region VII in Figure 6. The diagram shown in the upper right of Figure 7 is a view of the electrode finger 19 in the direction of arrow a1. Unlike Figures 2 to 5, the dimension lines indicating the range of the central region RC and the edge region RE are shown at the position of the upper surface 7a of the piezoelectric element 7 (excluding the recess 21). Although Figure 7 focuses on only one electrode finger 19, the other electrode fingers 19 may be similar. Also, although Figure 7 focuses on the edge region RE on the tip side of the electrode finger 19, the edge region RE on the base side of the electrode finger 19 may be similar, as long as it does not create inconsistencies.

[0083] Figure 7 shows an example where the electrode fingers 19 are relatively thin in the edge region RE, as in elastic wave apparatus 1B or 1C, and the electrode fingers 19 are relatively narrow in the edge region RE, as in electrode layer 5E. However, the explanation here may be applied to other embodiments as long as no inconsistencies arise.

[0084] At least one of the multiple sides of the recess 21 may be inclined with respect to the D3 direction. In Figure 7, the side of the recess 21 on the central region RC side is inclined such that the upward (+D3 side) is closer to the central region RC (or, from another viewpoint, the outer periphery of the recess 21). Let α1 be the angle formed by the side of the recess 21 on the central region RC side and the upper surface (D1D2 plane) of the piezoelectric element 7 on the side of the recess 21 and below. The magnitude of the angle α1 is arbitrary. For example, the angle α1 may be 60° or more, 70° or more, or 80° or more, and may also be less than 90°, 88° or less, or 85° or less. The above lower and upper limits may be combined in any way. For the sake of clarity, the side of the recess 21 on the central region RC side may be parallel to the D3 direction, and the angle α1 may be greater than 90°. The above description may be applied to any other side of the recess 21.

[0085] The portion of the electrode finger 19 in the central region RC is sometimes referred to as the central portion 19a, and the portion that is thinner than the central portion 19a (for example, the portion located in the edge region RE) is sometimes referred to as the low-profile portion 19b. The side surface of the low-profile portion 19b may be sloped such that the width of the electrode finger 19 narrows towards the top (+D3 side). In other words, as shown in the upper right of Figure 7, the cross-sectional shape of the low-profile portion 19b may be trapezoidal. In the low-profile portion 19b, when the angle formed by the side surface and the top surface (D1D2 plane) outside and below the electrode finger 19 is α2, the magnitude of angle α2 is arbitrary. For example, the example range of angle α1 above may be applied to angle α2. For clarification, the side surface of the low-profile portion 19b may be parallel to the D3 direction, and angle α2 may be greater than 90°. The above explanation may also be applied to the tip surface when the low-profile portion 19b includes the tip surface of the electrode finger 19.

[0086] The sides of the lower portion 19b may be more inclined than the sides of the central portion 19a. In other words, in the central portion 19a, if α3 is the angle formed by the side and the top surface (D1D2 plane) outside and below the electrode finger 19, then angle α2 may be smaller than angle α3. In this case, the sides of the central portion 19a may be parallel to the D3 direction, or they may be inclined in a direction that causes the width of the electrode finger 19 to narrower towards the top. In other words, the shape of the central portion 19a may be rectangular or trapezoidal. For the sake of clarity, angle α3 may be greater than 90°. When angle α2 is smaller than angle α3, the difference between the two is arbitrary, for example, it may be 0.5° or more, 1° or more, or 5° or more.

[0087] The end face of the central portion 19a on the side of the low-profile portion 19b may be inclined such that the central portion 19a becomes shorter as it rises. From another viewpoint, in the electrode finger 19, the surface rising from the upper surface of the edge region RE to the upper surface of the central region RC may be inclined with respect to the normal to the upper surface 7a (D3 axis) such that it is positioned closer to the central region RC as it rises. The degree of this inclination is arbitrary. For example, if the angle formed by the above end face (or rising surface) and the upper surface (D1D2 plane) of the central portion 19a on the low-profile portion 19b side and below is α4 (indicated by a symbol in Figure 8), then the explanation of the magnitude of angle α2 may be used in conjunction with angle α4. For the sake of clarity, angle α4 may be 90° or greater.

[0088] The various inclined surfaces described above do not necessarily have to be planar; for example, they may include multiple planes or multiple curved surfaces. In such cases, when determining whether the angles α1 to α4, etc., according to the embodiment are applied as angles to the inclined surfaces of the product, the various angles may be specified appropriately (for example, rationally in light of the effects of the various angles). For example, in an enlarged image of a cross-section perpendicular to the edge formed by the inclined surface in a plan view, an approximate straight line that fits the inclined surface may be obtained by regression analysis (for example, using the least squares method), and the angle of that approximate straight line may be referred to. The angle may be obtained from a single cross-sectional image, or a representative value (for example, the mean value) from multiple (for example, five or more) cross-sectional images may be referred to. If it is difficult to obtain multiple cross-sectional images from a single product, multiple cross-sectional images may be obtained from multiple products intended to have the same configuration.

[0089] When determining whether the lengths according to the embodiment are applied as various lengths in the actual product, if it is necessary to consider the effect of inclined surfaces (when precision is required), the various lengths may be specified appropriately (for example, reasonably in light of the effects of the various lengths). For example, when specifying the length L of the edge region RE in the D2 direction, and the boundary between the edge region RE and the central region RC is specified based on the recess 21, the position of the upper end of the side surface (inclined surface) on the central region RC side of the recess 21 may be referenced as the position of the side surface in the D2 direction. When specifying the boundary between the edge region RE and the gap region RG based on the tip surface of the electrode finger 19, the position of the lower end of the tip surface (inclined surface) of the electrode finger 19 may be referenced as the position of the tip surface (inclined surface) in the D2 direction. In addition, although different from the inclined surfaces described above, if the side surface of the recess 21 on the central region RC side and the tip surface of the electrode finger 19, etc., are not straight in a plan view, the position may be referenced such that the edge region RE is maximized, while excluding specific or accidental shapes. If the depth of the recess 21 is not uniform, the average value may be used, excluding any specific or accidental portions.

[0090] (5.3. Other examples of electrode layer materials) The upper and lower panels of Figure 8 are cross-sectional views showing other examples of the material for the electrode layer 5. Figure 8 corresponds to the line VIII-VIII in Figure 3. That is, Figure 8 shows a longitudinal section of the electrode finger 19 near the boundary between the central region RC and the edge region RE (near the boundary between the central portion 19a and the low-profile portion 19b). For convenience, the electrode layers 5 shown in Figure 8 will be referred to as electrode layers 5H and 5I. Electrode layers 5H and 5I may be applied to, for example, any of the acoustic wave apparatuses 1B to 1D according to the second to fourth examples (i.e., examples in which a part of the electrode layer 5 is thinned).

[0091] The electrode layer 5H has, in order from the piezoelectric element 7 side, a first layer 25A, a second layer 25B, and a third layer 25C. The upper surface of the low-profile portion 19b is made of the second layer 25B. The upper surface of the central portion 19a may be made of, for example, the third layer 25C. The material of the second layer 25B is different from the materials of the first layer 25A and the third layer 25C, and more specifically, it is less susceptible to etching than the materials of the first layer 25A and the third layer 25C. In other words, the second layer 25B functions as an etching stop layer. The thicknesses of the first layer 25A to the third layer 25C are arbitrary, as can be understood from the explanation of Figures 11 to 14 described later (the same applies to the electrode layer 5I).

[0092] Each layer (25A, 25B, or 25C) is composed of, for example, one type of material. However, at least one layer may be composed of layers made of different materials stacked together. In this embodiment, the difference in material of the second layer 25B from the material of the first layer 25A or the third layer 25C may be said to be that the materials of any of the layers contained within each layer (25A, 25B, or 25C) are different from each other. Also, contrary to the above description, for example, any layer located below the second layer 25B may be considered as the first layer 25A, and any layer located above the second layer 25B may be considered as the third layer 25C.

[0093] The materials for the first layer 25A to the third layer 25C may be selected as appropriate. For example, the materials for the first layer 25A and the third layer 25C may be the same or different. The material for the second layer 25B may be, for example, titanium (Ti) or chromium (Cr) or an alloy mainly composed of these. Ti and Cr have higher resistance to various etching processes (dry etching and wet etching) compared to other metals. The materials for the first layer 25A and the third layer 25C may be, for example, Al or an alloy mainly composed of Al.

[0094] The electrode layer 5I has a lower layer 27A and an upper layer 27B, in that order from the piezoelectric body 7 side. The upper surface of the low-profile portion 19b and the upper surface of the central portion 19a are both composed of the upper layer 27B, for example. The density of the upper layer 27B is lower than the density of the lower layer 27A. In this case, for example, compared to the case where the density of the upper layer 27B is relatively high, the effect of variations in the thickness of the low-profile portion 19b on the mass of the low-profile portion 19b is reduced.

[0095] Each layer (27A or 27B) is composed of, for example, one type of material. However, at least one layer may be composed of layers made of different materials stacked together. In this embodiment, the average density may be used as the density of the lower layer 27A and the density of the upper layer 27B. Also, contrary to the above description, the layer constituting the upper surface of the low-profile portion 19b may be considered as the upper layer 27B, and some or all of the layers located below the upper layer 27B may be considered as the lower layer 27A. The electrode layer 5H and the electrode layer 5I may be combined.

[0096] The materials of the lower layer 27A and the upper layer 27B may be selected as appropriate. For example, the electrode layer 5I may have Ti (lower layer 27A) and Al-Cu alloy (upper layer 27B). Alternatively, for example, the electrode layer 5I may have Ti (underlying layer) / CuAl2 / Ti (diffusion reduction layer) / Al-Cu alloy in that order from the piezoelectric body 7 side. The densities may be, for example, CuAl2 > Ti > Al-Cu alloy. In this case, for example, the Al-Cu alloy may be the upper layer 27B and any other layer may be the lower layer 27A, or the Ti (diffusion reduction layer) may be the upper layer 27B and the CuAl2 may be the lower layer 27A.

[0097] (6. Examples) (6.1. Examples of characteristics of comparative examples and embodiments) The upper and lower graphs in Figure 9 show examples of the characteristics of the comparative example and the embodiment. In these graphs, the horizontal axis represents frequency (MHz). In the upper graph, the vertical axis is a logarithmic scale showing the absolute value of impedance |Z| (Ω). In the lower graph, the vertical axis represents the phase (°) of impedance. Line Ln0 shows the characteristics of the comparative example. Line Ln1 shows the characteristics of the embodiment. The comparative example is a configuration in which the recess 21 is eliminated in elastic wave apparatus 1A and a dummy electrode 23 (length greater than 0.25p) is provided. The embodiment has the same configuration as elastic wave apparatus 1C. In terms of other conditions, the comparative example and the embodiment are basically the same.

[0098] As shown in the upper graph, the impedance characteristics of the elastic wave device 1 (1-port elastic wave resonator) exhibit a resonance point where the absolute value of the impedance is minimum (around 1910 MHz in the illustrated example) and an anti-resonance point where the absolute value of the impedance is maximum (around 2010 MHz in the illustrated example). The frequency of the resonance point is the resonance frequency. The frequency of the anti-resonance point is the anti-resonance frequency. The anti-resonance frequency is, for example, higher than the resonance frequency.

[0099] Let the bandwidth between the resonant frequency and the anti-resonant frequency be defined as bandwidth BC. Let the bandwidth below the resonant frequency be defined as bandwidth BL. Let the bandwidth above the anti-resonant frequency be defined as bandwidth BH. In this case, the better the characteristics of the elastic wave device 1 as a resonator, the closer the impedance phase in bandwidth BC will be to 90°, and the closer the impedance phase in bandwidths BL and BH will be to -90°.

[0100] As shown in the upper and lower graphs, the formation of the recess 21 reduces spurious emissions in the BC and BH bands. From another perspective, losses are reduced. Furthermore, this effect is achieved even when the portions located in the edge region RE and gap region RG of the electrode finger 19, as well as at least a portion of the busbar 17 on the electrode finger 19 side, are thinned.

[0101] (6.2. Definition of FOM) To evaluate the characteristics of embodiments where the values ​​of various parameters differ from one another, the Figure of Merit (FOM) was defined as follows, using the impedance phase θ(°). FOM = (90 - average value of θ in the bandwidth BL) × (Average value of θ in a 90-band BH) × (90 + minimum value of θ in bandwidth BC) × (Average value of θ in band BC - 85) / (180×180×180) / 5

[0102] If the characteristics of the elastic wave device 1 are ideally high, the value of FOM will be 1, as shown below. FOM=(90-(-90)) ×(90-(-90)) ×(90+90) ×(90-85) / (180×180×180) / 5 =1 And as the characteristics deteriorate, the FOM value becomes smaller.

[0103] (6.3. Example of FOM calculation) Figures 10 to 14 are contour plots showing examples of FOM calculation results. The characteristics (phase θ) that form the basis of the FOM calculation are obtained through simulation calculations. In these figures, the horizontal axis represents the length L of each edge region RE in the D2 direction, and its unit is pitch p. The vertical axis represents the depth D of the recess 21, and its unit is pitch p. The characteristics shown by the contour lines are FOM.

[0104] Figures 10 to 14 show that the thickness of the thinned portion (e.g., the low-profile portion 19b) of the electrode layer 5 differs from that of the other. Specifically, the ratio P (=dt / D × 100) of the difference dt (Figure 8) between the thick and thin portions of the electrode layer 5 with respect to the depth D of the recess 21 is set as follows: Figure 10: P=0% Figure 11: P=25% Figure 12: P=50% Figure 13: P=75% Figure 14: P=100%

[0105] In the electrode layer 5, the thinned area is the same as in the elastic wave apparatus 1C. That is, the portion located in the edge region RE and gap region RG of the electrode finger 19, and at least a portion of the busbar 17 on the electrode finger 19 side are thinned. However, since P=0% in Figure 10, the electrode layer 5 is the same as that of the elastic wave apparatus 1A. The shape of the recess 21 is the same as that of the elastic wave apparatuses 1A to 1C.

[0106] The conditions for the simulation calculations related to the example are shown below. • Piezoelectric element 7 Material: 42° Y-cut X-propagation LT Thickness: 0.4p • Middle layer 9 ·Material: SiO2 Thickness: 0.2p • Support substrate 11 ·Material: Si Thickness: Sufficiently thick ·Electrode finger 19 ·Material: Al Thickness in the central RC region: 0.16p Pitch p: 1.0 μm Duty: 0.5 Width of the intersection region RR (D2 direction): 30p • Edge region RE length L: 0.50p to 2.50p (in 0.50p increments) • Depth D of recess 21: 0.010p~0.040p (in increments of 0.010p) It was assumed that the electrode fingers 19 were arranged infinitely. The bandwidth BC, etc., were determined based on the characteristics obtained from the simulation results (i.e., the bandwidth BC, etc., differs slightly depending on the length L and depth D).

[0107] In all of Figures 10 to 14, there exist values ​​for length L and depth D such that the FOM can be 0.40 or greater when the length L is between 0.50p and 2.50p and the depth D is between 0.010p and 0.040p. Therefore, as described in the second point of view in the overview of the embodiment, L and D may be set to be within the above range.

[0108] A comparison of Figures 10 to 14 reveals that as the amount dt (P(%)) of thinning the electrode layer 5 increases, the region with relatively high FOM tends to be located in the upper right of the figure (towards the side where L and D are larger). Furthermore, the range in which FOM is 0.40 or higher is relatively similar for 25% and 50%, and for 75% and 100%. Therefore, L and D may be set as follows according to P(%).

[0109] ·0%(1): 0.50p ≤ L ≤ 1.70p, and 0.010p ≤ D ≤ 0.040p, or, ·0%(2): 1.60p≦L≦2.50p, and 0.010p ≤ D ≤ 0.015p • Greater than 0% and less than or equal to 50%: 0.60p ≤ L ≤ 2.30p, and 0.013p ≤ D ≤ 0.036p • Over 50% and under 100%: 0.85p ≤ L ≤ 2.50p, and 0.014p ≤ D ≤ 0.040p

[0110] In the above, the 0%(1) range roughly corresponds to the rectangular area encompassing the region where FOM is 0.40 or greater on the left side of Figure 10. The 0%(2) range roughly corresponds to the rectangular area encompassing the region where FOM is 0.40 or greater on the lower right side of Figure 10. The range between 0% and 50% roughly corresponds to the rectangular area encompassing the region where FOM is 0.40 or greater in both Figure 11 and Figure 12. The range between 50% and 100% roughly corresponds to the rectangular area encompassing the region where FOM is 0.40 or greater in both Figure 13 and Figure 14. P may be rounded to one of the above categories (the same applies hereafter).

[0111] In the above, P was classified into three types, but it is also possible to classify P in more detail, associate it with one of Figures 10 to 14, and select L and D located in the region where FOM is 0.40 or greater in each figure. For example, it may be done as follows. 0%: Figure 10 • Over 0% and less than 25%: Figure 10 or Figure 11 25%: Figure 11 • Over 25% and less than 50%: Figure 11 or Figure 12 50%: Figure 12 • Over 50% but less than 75%: Figure 12 or Figure 13 75%: Figure 13 • Over 75% but less than 100%: Figure 13 or Figure 14 ·100%: Figure 14

[0112] If the drawings used above are specified as "or", then it is sufficient that L and D are located in an area where FOM is 0.40 or greater in either drawing. Note that "or" may be replaced with "and". That is, L and D may be located in an area where FOM is 0.40 or greater in both drawings. And / or, in the above, the requirement may be "0.60 or greater" instead of "0.40 or greater". Boundaries may be treated as being included in areas with high FOM (the same applies to lines connecting coordinates as described below).

[0113] The approximate coordinates (L,D) of the outer corners of the regions where FOM is 0.40 or greater in Figures 10 to 14 are shown below. The coordinates are shown in clockwise order. Instead of the regions where FOM is 0.40 or greater in Figures 10 to 14, the regions obtained by connecting the following coordinates in order may be used. Left side of Figure 10: (0.50, 0.019), (0.50, 0.022), (0.65, 0.030), (0.50, 0.034), (0.50, 0.040), (0.70, 0.040), (1.00, 0.035), (1.17, 0.030), (1.25, 0.025), (1.50, 0.025), (1.68, 0.023), (1.66, 0.020), (1.50, 0.012), (1.10, 0.010), (0.96 0.010) • Bottom right of Figure 10: (1.59, 0.010), (2.00, 0.014), (2.23, 0.014), (2.50, 0.013), (2.50, 0.010) Figure 11: (0.50, 0.029), (0.50, 0.040), (0.55, 0.040), (1.00, 0.036), (1.50, 0.036), (1.88, 0.030), (1.88, 0.027), (2.00, 0.028), (2.28, 0.025), (2.28, 0.020), (2.23, 0.014), (2.50, 0.015), (2.50, 0.010), (1.60, 0.010), (1.50, 0.012), (1.18, 0.013), (1.00, 0.013), (0.83, 0.016), (0.76, 0.020), (0.79, 0.026) Figure 12: (0.63, 0.023), (0.63, 0.030), (0.78, 0.035), (1.15, 0.037), (1.25, 0.040) (1.61, 0.040), (1.86, 0.030), (1.81, 0.026), (2.00, 0.028), (2.28, 0.025), (2.29, 0.020), (2.00, 0.015), (1.64, 0.013), (1.50, 0.015), (1.00, 0.018), (0.94, 0.019), (0.74, 0.020) Figure 13: (0.74, 0.040), (1.68, 0.040), (2.00, 0.035), (2.23, 0.030), (2.18, 0.024), (2.50, 0.022), (2.50, 0.010), (2.34, 0.010), (2.14, 0.013), (2.00, 0.012), (1.50, 0.019), (1.43, 0.019), (1.16, 0.020), (1.00, 0.021), (0.81, 0.026), (0.76, 0.030) Figure 14: (0.85, 0.040), (1.88, 0.040), (2.45, 0.030), (2.38, 0.027), (2.50, 0.029), (2.50, 0.014), (2.25, 0.015), (2.00, 0.017), (1.73, 0.014), (1.64, 0.020), (1.50, 0.022), (1.21, 0.024), (1.00, 0.036)

[0114] Similarly, the approximate coordinates (L,D) of the outer corners of the regions where FOM is 0.60 or greater in Figures 10 to 14 are shown below. Instead of the regions where FOM is 0.60 or greater in Figures 10 to 14, the regions obtained by connecting the following coordinates in order may be used. Figure 10: (1.90, 0.010), (2.00, 0.011), (2.06, 0.011), (2.23, 0.010) Figure 11: (1.00, 0.025), (1.50, 0.030), (1.51, 0.020), (2.00, 0.024), (2.13, 0.022), (2.13, 0.020), (2.01, 0.010), (2.50, 0.011), (2.50, 0.010), (1.98, 0.010), (1.80, 0.016), (1.50, 0.020), (1.00, 0.019), (0.98, 0.020) Figure 12: (1.68, 0.020), (2.00, 0.023), (2.10, 0.022), (2.11, 0.020), (2.00, 0.018), (1.86, 0.017) Figure 13: (1.50, 0.030), (1.61, 0.038), (2.00, 0.032), (2.08, 0.030), (2.01, 0.020), (2.10, 0.020), (2.00, 0.019), (1.95, 0.020), (1.78, 0.026) • Upper part of Figure 14: (1.35, 0.040), (1.61, 0.040), (2.15, 0.030), (2.00, 0.025), (1.85, 0.027), (1.50, 0.035) • Bottom right of Figure 14: (2.50, 0.019), (2.45, 0.019), (2.34, 0.020), (2.50, 0.021)

[0115] Note that areas with values ​​of 0.80 or higher appear at the right edge of Figure 13 and the lower left corner of Figure 14. For coordinates where the FOM value is 0.40 or higher or 0.60 or higher, these areas were ignored. Of course, L and D located within these areas could also be selected.

[0116] As can be seen from the comparison between Figure 10, where the electrode layer 5 is not thinned, and Figures 11 to 14, where a portion of the electrode layer 5 is thinned, the latter is more likely to show regions where the FOM is 0.60 or higher compared to the former. Also, for example, the latter tends to have a larger area of ​​regions where the FOM is 0.40 or higher compared to the former. This contradicts the effect expected from the technology that utilizes the piston mode by hammer shape, as described in the overview of the embodiment.

[0117] (7. Manufacturing method of elastic wave apparatus) The manufacturing method for the elastic wave apparatus 1 may vary, except for the method of thinning a portion of the electrode layer 5, and may be a known method, for example. Therefore, here we will describe the method of thinning the electrode layer 5.

[0118] Figure 15 is a schematic cross-sectional view showing a method for thinning the electrode layer 5, and roughly corresponds to the cross-section along line VIII-VIII in Figure 3. However, in the D2 direction, Figure 15 shows a slightly wider range towards +D2 than the range shown by line VIII-VIII. The upper panel shows the state before the electrode layer 5 is thinned, and the lower panel shows the state after the electrode layer 5 has been thinned. In Figure 15, the range in which the recess 21 is formed and the range in which the electrode layer 5 is thinned are exemplified by the elastic wave apparatus 1C in Figure 4.

[0119] As shown in the upper figure, first, an electrode layer 5 of uniform thickness is formed on the upper surface 7a of the piezoelectric substrate 3 (piezoelectric body 7), where the recess 21 is not formed. The planar shape of the electrode layer 5 is the same as in Figures 2 to 5. That is, the IDT electrode 13 is formed by etching.

[0120] Next, as shown in the upper diagram, a resist 29 (etching resist, etching mask) is formed. The resist 29 has openings in the region where the recess 21 is formed and in the region where the electrode layer 5 is thinned. In other words, the region where the recess 21 is formed and the region where the electrode layer 5 is thinned are considered non-placement regions of the resist 29.

[0121] Next, as shown in the lower diagram, etching is performed through the resist 29 (more precisely, its non-placed areas). At this time, both the piezoelectric element 7 and the electrode layer 5 are etched. Then, the recess 21 is formed, and a portion of the electrode layer 5 is thinned.

[0122] The opening (non-placement area) of the resist 29 may be set appropriately so as to realize the configurations of the elastic wave apparatus 1B to 1D. For example, in elastic wave apparatus 1B, the opening of the resist 29 extends across the edge region RE and the gap region RG. In elastic wave apparatus 1C, the opening of the resist 29 extends across the edge region RE, the gap region RG, and at least the area of ​​the busbar 17 on the side of the electrode finger 19. In elastic wave apparatus 1D, the opening of the resist 29 extends across the edge region RE. In any of the elastic wave apparatuses 1B to 1D, the opening of the resist 29 is, for example, a strip-shaped (e.g., rectangular) shape with a constant width (in the D2 direction) and extending parallel to the D1 direction.

[0123] In cases where the electrode layer 5 is not thinned (for example, in the elastic wave apparatus 1A), the opening in the resist 29 extends over the region where the recess 21 is formed. Its shape is the same as the shape of the recess 21.

[0124] Etching may be dry etching or wet etching. The specific type of dry etching is also arbitrary. For example, dry etching may utilize chemical reactions, physical actions, or a combination of both. More detailed examples include reactive ion etching, gas etching, plasma etching, and ion milling. The material of the resist 29 is arbitrary; for example, photoresist (photosensitive resin) may be used.

[0125] The ratio of the amount dt used to thin the electrode layer 5 to the depth D of the recess 21 (P(%)=dt / D×100) can be adjusted by appropriately selecting etching conditions. Examples of etching conditions include, in the case of dry etching, the type of gas, the flow rate and pressure of the etching gas, the power and frequency used to generate the plasma, the bias voltage applied to the wafer, the temperature of the chamber and substrate, and the etching time. In addition, an etching stop layer (second layer 25B) may be used, as shown in the electrode layer 5H in Figure 8.

[0126] Contrary to the above explanation, dt / D does not necessarily need to be actively adjusted. For example, the etching conditions may be set so that either D or dt is a desired value, and the other value may be a value that is consequently obtained by those etching conditions. Then, the desired FOM may be obtained by setting L based on the values ​​of D and dt.

[0127] The planar shapes in Figures 6 and 7 may be realized, for example, in etching that forms the electrode layer 5 before etching in Figure 15. Depending on the etching conditions in Figure 15, the electrode layer 5 may not only become thinner in some areas, but its sides may also be etched. This etching may be used to realize a shape in which a portion of the electrode fingers 19 in the electrode layer 5E becomes thinner.

[0128] The inclination of the side surface of the recess 21 and the inclination of the various surfaces of the electrode finger 19, as described with reference to Figures 7 and 8, may be achieved, for example, by appropriately setting the etching conditions in Figure 15. When the side surface of the low-profile portion 19b is inclined more than the side surface of the central portion 19a, the etching conditions in Figure 15 may be set to make it easier for the side surface to be inclined, compared to the etching conditions in Figure 15 for forming the planar shape of the electrode layer 5 before etching.

[0129] The above-described method for manufacturing the elastic wave apparatus 1 is merely an example, and the elastic wave apparatus 1 may be manufactured by other methods. For example, the etching to form the recess 21 and the etching to thin the electrode layer 5 may be performed separately. In this case, the etching of the recess 21 may be performed either before or after forming the electrode layer 5. Furthermore, for example, the electrode layer 5 may be realized by performing a process of forming a conductive layer through a first mask across a region to be thinned and a region to be thickened, and a process of forming a conductive layer through a second mask only in the region to be thickened. Theoretically, it is also possible to manufacture the elastic wave apparatus 1A by forming electrode fingers 19 that are relatively thickened in the edge region RE and then thinning them by etching to form the recess 21.

[0130] (8. Examples of applications of elastic wave devices) (8.1. Filters) Figure 16 is a plan view of filter 31 as an application example of elastic wave apparatus 1. In this figure, elastic wave apparatus 1 is indicated by the symbols of the resonators 35 (35P and 35S). Filter 31 has multiple resonators 35 (elastic wave apparatus 1), with five shown as an example in Figure 16. Contrary to the above explanation, filter 31 may also be considered as an example of a single elastic wave apparatus.

[0131] Filter 31 filters the electrical signal input to one of terminals 33A and 33B and outputs it to the other. Filter 31 has, for example, a ladder-type filter configured by connecting a plurality of resonators 35 in a ladder configuration between terminals 33A and 33B. The ladder-type filter has a plurality (or even just one) of resonators 35S (series resonators) connected in series between terminals 33A and 33B, and a plurality (or even just one) of resonators 35P (parallel arms, parallel resonators) connecting the series line (series arm) to a reference potential.

[0132] Filter 31 may have other types of filters in addition to, or instead of, the ladder-type filter described above. For example, filter 31 may have a multimode filter (as described above). Alternatively, for example, the resonator 35 and the multimode filter may be connected in series.

[0133] Each resonator 35, as described above, has a piezoelectric substrate 3 (piezoelectric body 7), an electrode layer 5 (IDT electrode 13), and end faces 7b on both sides (or one side) thereof. Multiple resonators 35 share, for example, the piezoelectric substrate 3 (piezoelectric body 7).

[0134] (8.2. Communication equipment) Figure 17 is a block diagram showing the main components of a communication device 41 having filters 31 (31T and 31R). The communication device 41 performs wireless communication, for example, via an antenna 45. The filters 31 (31T and 31R) are used, for example, in a demultiplexer 43 interposed between the antenna 45 and an RF-IC (Radio Frequency Integrated Circuit) 47.

[0135] The demultiplexer 43 has a transmit filter 31T and a receive filter 31R. Each of these has a configuration as described, for example, with reference to Figure 16. The terminal for transmitting the signal of the transmit filter 31T (a terminal on the antenna 45 side, e.g., 33A or 33B) and the terminal for receiving the signal of the receive filter 31R (a terminal on the antenna 45 side, e.g., 33A or 33B) are shared.

[0136] The transmitting filter 31T and the receiving filter 31R may or may not share the piezoelectric substrate 3. In the former case, and in the embodiment where the piezoelectric element 7 is supported on the support substrate 11, the transmitting filter 31T and the receiving filter 31R may or may not share the piezoelectric element 7. Furthermore, each filter 31 may be distributed across two or more piezoelectric elements 7 (or piezoelectric substrate 3).

[0137] In the communication device 41, the transmission information signal TIS, which contains the information to be transmitted, is modulated and its frequency is increased (converted to a high-frequency signal with a carrier frequency) by the RF-IC 47 to become the transmission signal TS. The transmission signal TS has unwanted components other than the transmission passband removed by the bandpass filter 49, is amplified by the amplifier 51, and is input to the demultiplexer 43 (transmission filter 31T). The transmission filter 31T then removes unwanted components other than the transmission passband from the input transmission signal TS and outputs the transmission signal TS after removal to the antenna 45. The antenna 45 converts the input electrical signal (transmission signal TS) into a radio signal (radio wave) and transmits it.

[0138] Furthermore, in the communication device 41, the radio signal (radio wave) received by the antenna 45 is converted into an electrical signal (received signal RS) by the antenna 45 and input to the demultiplexer 43. The receiving filter 31R removes unwanted components other than the passband for reception from the input received signal RS and outputs it to the amplifier 53. The output received signal RS is amplified by the amplifier 53, and unwanted components other than the passband for reception are removed by the bandpass filter 55. The received signal RS is then frequency-downgraded and demodulated by the RF-IC 47 to become the received information signal RIS.

[0139] The transmitted information signal TIS and the received information signal RIS may be low-frequency signals (baseband signals) containing appropriate information, such as analog or digitized audio signals. The passband of the wireless signal may be set as appropriate. The modulation method may be phase modulation, amplitude modulation, frequency modulation, or a combination of two or more of these. The circuit method shown as an example is a direct conversion method, but any other appropriate method may be used, such as a double superheterodyne method. Furthermore, Figure 17 schematically shows only the essential parts, and low-pass filters, isolators, etc. may be added at appropriate positions, or the positions of amplifiers, etc. may be changed.

[0140] (9. Summary of Embodiments) Below, we will extract the configuration of the embodiment and describe examples of the effects of the extracted configuration. Note that the exemplified effects do not necessarily have to be achieved by the extracted configuration.

[0141] The elastic wave apparatus 1 comprises a piezoelectric body 7 having an upper surface 7a (an example of a first surface) and an IDT electrode 13 located on the upper surface 7a. The IDT electrode 13 has busbars 17A and 17B (examples of a first busbar and a second busbar) and a plurality of electrode fingers 19A and 19B (examples of a first electrode finger and a second electrode finger). The busbars 17A and 17B face each other. The plurality of electrode fingers 19A extend in parallel from the busbar 17A toward the busbar 17B. The plurality of electrode fingers 19B extend in parallel from the busbar 17B toward the busbar 17A and are located between the plurality of electrode fingers 19A. The intersection region RR where the electrode fingers 19A and electrode fingers 19B overlap when viewed in the direction of elastic wave propagation (D1 direction) comprises a central region RC and edge regions RE_A and RE_B (examples of a first edge region and a second edge region). The central region RC is located on the central side in the opposing direction (D2 direction) of the bus bars 17A and 17B. The edge region RE_A is located on the side of bus bar 17A. The edge region RE_B is located on the side of bus bar 17B. In the edge region RE_B, the piezoelectric element 7 has a recess 21 between electrode fingers 19A and 19B.

[0142] In the first respect, the thickness of the electrode finger 19A in the edge region RE_B may be thinner than the thickness of the electrode finger 19A in the central region RC (elastic wave apparatus 1B~1D).

[0143] Furthermore, in the manufacturing method of the elastic wave apparatus 1 according to the first aspect, the region of the upper surface 7a in which the recess 21 is formed and the portion of the electrode finger 19A located in the edge region RE_B may both be etched.

[0144] In this case, for example, contrary to the expected effect based on the technique of utilizing the piston mode by hammer shape as described above, regions with an FOM of 0.60 or higher tend to appear, and the area of ​​regions with an FOM of 0.40 or higher tends to be larger. Also, as explained with reference to Figure 15, etching can be performed over the entire edge region RE_B, rather than just on the region between the electrode fingers 19 of the edge region RE_B (the region that becomes the recess 21). As a result, for example, the difficulty of etching is reduced compared to the elastic wave apparatus 1A (from another perspective, accuracy is improved). For example, the need to consider etching errors in the D1 direction is reduced. Also, for example, when dry etching is performed on a narrow region, the inner surface of the opening of the resist 29 tends to affect the gas flow, increasing the probability that the intended shape cannot be obtained, but such a probability is reduced.

[0145] The difference dt between the thickness of the electrode finger 19A in the edge region RE_B and the thickness of the electrode finger 19A in the central region RC may be smaller than the depth D of the recess 21.

[0146] In this case, for example, as can be seen from the comparison between Figures 11-13 and Figure 14, it is easier to widen the region where FOM is 0.40 or higher. As a result, for example, the degree of design freedom is improved. Also, for example, when the manufacturing method described with reference to Figure 15 is performed, it means that the etching rate of the electrode finger 19A is lower than the etching rate of the piezoelectric material 7. Therefore, for example, it is possible to reduce manufacturing variations in the thickness of the edge region RE_B of the electrode finger 19A and improve yield.

[0147] The IDT electrode 13 may include, in order from the piezoelectric body 7 side, a first layer 25A, a second layer 25B, and a third layer 25C. The material of the second layer 25B may be different from the material of the first layer 25A and the third layer 25C. The upper surface of the edge region RE_B of the electrode finger 19A may be made of the second layer 25B.

[0148] In this case, for example, the speed of sound in the central region RC and the speed of sound in the edge region RE_B can be adjusted by selecting the material of each layer. Also, for example, when the electrode finger 19A is thinned in the edge region RE_B by etching, the second layer 25B can be made to function as an etching stop layer. As a result, dt (dt / D) can be set to any value.

[0149] The IDT electrode 13 may have, in order from the piezoelectric body 7 side, a lower layer 27A and an upper layer 27B with a lower density than the lower layer 27A. The upper surface of the edge region RE_B of the electrode finger 19A may be formed by the upper layer 27B.

[0150] In this case, for example, the manufacturing variation in the thickness (or difference dt) of the electrode finger 19A in the edge region RE_B has a reduced effect on the mass of the electrode finger 19A in the edge region RE_B. As a result, for example, the characteristics of the elastic wave apparatus 1 can be more easily stabilized.

[0151] Let the length in the direction in which the electrode finger 19A extends of the portion of the recess 21 located within the edge region RE_B be L, let the depth of the recess 21 be D, let the amount by which the thickness of the electrode finger 19A in the edge region RE_B is thinner than the thickness in the central region RC of the electrode finger 19A be dt, and let P = dt / D × 100. In this case, any of the following may hold. · 0% < P < 25% and L and D are located in a range where the FOM is 0.40 or more in FIG. 10 or FIG. 11, · P = 25% and L and D are located in a range where the FOM is 0.40 or more in FIG. 11, · 25% < P < 50% and L and D are located in a range where the FOM is 0.40 or more in FIG. 11 or FIG. 12, · P = 50% and L and D are located in a range where the FOM is 0.40 or more in FIG. 12, · 50% < P < 75% and L and D are located in a range where the FOM is 0.40 or more in FIG. 12 or FIG. 13, · P = 75% and L and D are located in a range where the FOM is 0.40 or more in FIG. 13, · 75% < P < 100% and L and D are located in a range where the FOM is 0.40 or more in FIG. 13 or FIG. 14, or, · P = 100% and L and D are located in a range where the FOM is 0.40 or more in FIG. 14.

[0152] In this case, for example, the probability of obtaining a characteristic where the FOM is 0.40 or more is high.

[0153] In the electrode finger 19A, the surface rising from the upper surface in the edge region RE_B to the upper surface in the central region RC may be inclined with respect to the normal of the upper surface 7a in a direction where it is located closer to the central region RC toward the upper side.

[0154] In this case, for example, in the longitudinal cross-section of the electrode finger 19, the corner formed by the upper surface of the electrode finger 19A becomes gentler. As a result, for example, electric field concentration and / or stress concentration are less likely to occur on the electrode finger 19. Also, because the rising surface is inclined, the change in mass of the electrode finger 19 at the boundary between the central region RC and the edge region RE becomes gentler. As a result, for example, abrupt changes in the load applied to the upper surface 7a are reduced. Consequently, for example, improved durability of the upper surface 7a and reduced disturbance of elastic waves can be expected.

[0155] The thickness of the busbar 17B, at least on the side of the edge region RE_B, may be thinner than the thickness of the electrode finger 19A in the central region (elastic wave apparatus 1C).

[0156] In this case, for example, the electric field generated by the busbar 17B is reduced in the D3 direction, and the probability of unintended effects occurring due to this electric field is reduced. Furthermore, for example, focusing on the manufacturing method, as explained with reference to Figure 15, etching can be performed over a relatively wide area encompassing the edge region RE, the gap region RG, and at least a portion of the busbar 17. As a result, for example, the effect of reducing the etching difficulty described above is improved.

[0157] Furthermore, from a second perspective, let p be the repeating interval between the multiple electrode fingers 19A and the multiple electrode fingers 19B, let L be the length of the portion of the recess 21 located within the edge region RE_B in the direction in which the electrode finger 19A extends, and let D be the depth of the recess 21. At this time, 0.50p ≤ L ≤ 2.50p, and It is also acceptable that 0.010p ≤ D ≤ 0.040p.

[0158] In this case, for example, as explained with reference to Figures 10 to 14, there is a high probability of obtaining an FOM of 0.40 or higher.

[0159] Furthermore, as stated in Section 6.3, L and D may be defined within a narrower range than described above, depending on dt / D. This further increases the probability of obtaining an FOM of 0.40 or higher.

[0160] The recess 21 may extend between the edge region RE_B and the busbar 17B (i.e., the gap region RG).

[0161] In this case, for example, the volume of the piezoelectric element 7 is reduced in the gap region RG. From the first point of view, since the tip of the electrode finger 19A is thinned, the electric field formed between it and the busbar 17B is reduced in the D3 direction. As a result, the probability of the electric field in the gap region RG producing unintended effects is reduced. Also, for example, focusing on the manufacturing method, etching can be performed over a relatively wide area spanning the edge region RE and the gap region RG. Furthermore, for example, when combined with the second point of view, the conditions become closer to those of the simulation, increasing the probability of obtaining an FOM of 0.40 or higher.

[0162] The electrode finger 19A may have a narrower width in the edge region RE_B than in the central region RC.

[0163] In this case, for example, the mass of the electrode finger 19 is reduced in the edge region RE_B. Simulation calculations showed that the FOM improved by thinning the electrode finger 19 and reducing its mass in the edge region RE_B. Therefore, it is expected that the FOM will improve by a similar principle. Furthermore, in combination with the first viewpoint, the electrode finger 19 can be made thinner in the edge region RE_B simply by etching both the recess 21 and the electrode finger 19 in the edge region RE_B.

[0164] The electrode finger 19A may have a width in the edge region RE_B that is wider than its width in the central region RC.

[0165] In this case, for example, in the elastic wave device 1A, the mass in the edge region RE_B can be increased, thereby reducing the speed of sound in the edge region RE_B. As a result, for example, in combination with the second viewpoint, it is expected that the FOM will be improved. Furthermore, in combination with the first viewpoint, the change in mass due to the thinning of the electrode finger 19 in the edge region RE_B can be reduced. As a result, for example, the use of know-how from the prior art can be facilitated.

[0166] The side surface of the recess 21 facing the central region RC may be inclined with respect to the normal to the upper surface 7a (D3 axis), with the upper part being positioned closer to the central region RC.

[0167] In this case, for example, elastic waves propagating in the D2 direction near the boundary between the central region RC and the edge region RE can be reflected downward by the side surface of the recess 21. This reduces the likelihood of spurious emissions. Furthermore, since the corner formed by the side surface of the recess 21 and the upper surface 7a in a cross-section parallel to the D2D3 plane is gentle, stress concentration is less likely to occur in the piezoelectric element 7.

[0168] The electrode finger 19A may be inclined such that the side surface in the edge region RE_B is narrower towards the top than the side surface in the central region RC.

[0169] In this case, for example, in the cross-section of the electrode finger 19, the corner formed by the top surface and side surface of the electrode finger 19 becomes gentler, making it less likely for electric field concentration and / or stress concentration to occur on the electrode finger 19. In addition, it becomes easier to reduce the mass in the edge region RE of the electrode finger 19.

[0170] The elastic wave device 1 may utilize leaky waves or Rayleigh waves as the main components of the elastic waves.

[0171] In this case, for example, since the elastic wave energy is concentrated on the upper surface 7a, the thickness of the electrode finger 19 and / or the depth of the recess 21 have a relatively large influence on the elastic wave. As a result, the various effects described above from the first and second viewpoints are easily obtained.

[0172] The technology relating to this disclosure is not limited to the embodiments described above and may be implemented in various ways. For example, the types of electrode finger widths may be three or more, rather than just two.

[0173] The following concepts can be extracted from this disclosure. (Concept 1) A piezoelectric material having a first surface, The IDT electrode located on the first surface, It has, The IDT electrode is The first busbar and the second busbar are opposite each other, A plurality of first electrode fingers extending in parallel from the first busbar to the second busbar, It has a plurality of second electrode fingers that extend in parallel from the second busbar toward the first busbar and are positioned between the plurality of first electrode fingers, The intersection region where the first electrode finger and the second electrode finger overlap in the direction of elastic wave propagation is, A central region located on the central side in the opposing direction of the first busbar and the second busbar, A first edge region located on the side of the first busbar, It has a second edge region located on the side of the second busbar, The piezoelectric material has a recess between the first electrode finger and the second electrode finger in the second edge region. The thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region. Elastic wave device. (Concept 2) The difference between the thickness of the first electrode finger in the second edge region and the thickness of the first electrode finger in the central region is less than the depth of the recess. An elastic wave apparatus as described in Concept 1. (Concept 3) The IDT electrode includes, in order from the piezoelectric side, a first layer, a second layer, and a third layer. The material of the second layer is different from that of the third layer. The upper surface in the central region of the first electrode finger is constituted by the third layer. The upper surface in the second edge region of the first electrode finger is constituted by the second layer. The elastic wave device according to Concept 1 or 2. (Concept 4) The IDT electrode has, in order from the piezoelectric body side, a lower layer and an upper layer having a lower density than the lower layer. The upper surface in the second edge region of the first electrode finger is constituted by the upper layer. The elastic wave device according to any one of Concepts 1 to 3. (Concept 5) Let the length in the direction in which the first electrode finger extends of the portion of the recess located within the second edge region be L, the depth of the recess be D, the amount by which the thickness of the first electrode finger in the second edge region is thinner than the thickness in the central region of the first electrode finger be dt, and when P = dt / D × 100: 0% < P < 25%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 10 or FIG. 11. P = 25%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 11. 25% < P < 50%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 11 or FIG. 12. P = 50%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 12. 50% < P < 75%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 12 or FIG. 13. P = 75%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 13. 75% < P < 100%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 13 or FIG. 14, or P = 100%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 14. An elastic wave device described in any one of concepts 1 to 4. (Concept 6) In the first electrode finger, the surface rising from the upper surface of the second edge region to the upper surface of the central region is inclined with respect to the normal of the first surface, with the upper surface being positioned closer to the central region. An elastic wave device described in any one of concepts 1 to 5. (Concept 7) The thickness of the second busbar, at least on the side of the second edge region, is thinner than the thickness of the central region of the first electrode finger. An elastic wave device described in any one of concepts 1 to 6. (Concept 8) A piezoelectric material having a first surface, The IDT electrode located on the first surface, It has, The IDT electrode is The first busbar and the second busbar are opposite each other, A plurality of first electrode fingers extending in parallel from the first busbar to the second busbar, It has a plurality of second electrode fingers that extend in parallel from the second busbar toward the first busbar and are positioned between the plurality of first electrode fingers, The intersection region where the first electrode finger and the second electrode finger overlap in the direction of elastic wave propagation is, A central region located on the central side in the opposing direction of the first busbar and the second busbar, A first edge region located on the side of the first busbar, It has a second edge region located on the side of the second busbar, The piezoelectric material has a recess between the first electrode finger and the second electrode finger in the second edge region. When the repeating interval between the plurality of first electrode fingers and the plurality of second electrode fingers is p, the length of the portion of the recess located within the second edge region in the direction in which the first electrode finger extends is L, and the depth of the recess is D, 0.50p ≤ L ≤ 2.50p, and 0.010p ≤ D ≤ 0.040p Elastic wave device (Concept 9) The thickness of the first electrode finger in the second edge region is the same as the thickness of the first electrode finger in the central region, 0.50p ≤ L ≤ 1.70p, and 0.010p ≤ D ≤ 0.040p, or, 1.60p ≤ L ≤ 2.50p, and 0.010p ≤ D ≤ 0.015p The elastic wave device according to Concept 8 (Concept 10) The thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region by a difference that is more than 0% and at most 50% of the depth of the recess, 0.60p ≤ L ≤ 2.30p, and 0.013p ≤ D ≤ 0.036p The elastic wave device according to any one of Concepts 1 to 8 (Concept 11) The thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region by a difference that is more than 50% and at most 100% of the depth of the recess, 0.85p ≤ L ≤ 2.50p, and 0.014p ≤ D ≤ 0.040p The elastic wave device according to any one of Concepts 1 to 8 (Concept 12) When the amount by which the thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region is dt, and P is defined as dt / D × 100, P = 100%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 10, 0% < P < 25%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 10 or FIG. 11, P = 25%, and L and D are located in a range where the FOM is 0.40 or more in FIG. 11, 25% < P < 50%, where L and D are located in the range where the FOM is 0.40 or more in FIG. 11 or FIG. 12. P = 50%, where L and D are located in the range where the FOM is 0.40 or more in FIG. 12. 50% < P < 75%, where L and D are located in the range where the FOM is 0.40 or more in FIG. 12 or FIG. 13. P = 75%, where L and D are located in the range where the FOM is 0.40 or more in FIG. 13. 75% < P < 100%, where L and D are located in the range where the FOM is 0.40 or more in FIG. 13 or FIG. 14, or P = 100%, where L and D are located in the range where the FOM is 0.40 or more in FIG. 14 The elastic wave device according to any one of Concepts 1 to 11. (Concept 13) The recess extends between the second edge region and the second bus bar. The elastic wave device according to any one of Concepts 1 to 12. (Concept 14) The width of the first electrode finger in the second edge region is narrower than the width in the central region. The elastic wave device according to any one of Concepts 1 to 13. (Concept 15) The width of the first electrode finger in the second edge region is wider than the width in the central region. The elastic wave device according to any one of Concepts 1 to 13. (Concept 16) The side surface on the side of the central region of the recess is inclined with respect to the normal of the first surface in a direction where it is located closer to the central region upward. The elastic wave device according to any one of Concepts 1 to 15. (Concept 17) The side surface of the first electrode finger in the second edge region is inclined in a direction where the width of the first electrode finger becomes narrower upward compared to the side surface in the central region. The elastic wave device according to any one of Concepts 1 to 16. (Concept 18) Leaky waves or Rayleigh waves are used as the main components of elastic waves. An elastic wave device described in any one of Concepts 1-17. (Concept 19) On the second surface of the piezoelectric material, which is located opposite to the first surface, there is an intermediate layer with a lower sound velocity compared to the piezoelectric material. The intermediate layer further comprises a support substrate located on the opposite side of the piezoelectric element, and having a sound velocity faster than the piezoelectric element or the intermediate layer, When the repeating interval between the plurality of first electrode fingers and the plurality of second electrode fingers is p, the thickness of the piezoelectric body is 2p or less. An elastic wave device described in any one of Concepts 1-18. (Concept 20) An elastic wave apparatus described in any one of Concepts 1 to 19, The antenna connected to the aforementioned elastic wave device, An IC connected to the antenna via the elastic wave device, A communication device that has the following features. (Concept 21) A method for manufacturing an elastic wave apparatus as described in any one of concepts 1 to 19, The region of the first surface in which the recess is formed and the portion of the first electrode finger located in the second edge region are both etched. A method for manufacturing an elastic wave apparatus. [Explanation of Symbols]

[0174] 1...Elastic wave device, 3...Piezoelectric substrate, 5...Electrode layer, 7...Piezoelectric material, 7a...Top surface (first surface), 13...IDT electrode, 17A...Busbar (first busbar), 17B...Busbar (second busbar), 19A...Electrode finger (first electrode finger), 19B...Electrode finger (second electrode finger), 21...Recess, RC...Central region, RE_A...Edge region (first edge region), RE_B...Edge region (second edge region).

Claims

1. A piezoelectric body having a first surface, An IDT electrode located on the first surface, It has, The IDT electrode is The first busbar and the second busbar are opposite each other, A plurality of first electrode fingers extending in parallel from the first busbar to the second busbar, It has a plurality of second electrode fingers that extend in parallel from the second busbar toward the first busbar and are positioned between the plurality of first electrode fingers, The intersection region where the first electrode finger and the second electrode finger overlap in the direction of elastic wave propagation is, A central region located on the central side in the opposing direction of the first busbar and the second busbar, A first edge region located on the side of the first busbar, It has a second edge region located on the side of the second busbar, The piezoelectric material has a recess between the first electrode finger and the second electrode finger in the second edge region. The thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region. Elastic wave device.

2. The difference between the thickness of the first electrode finger in the second edge region and the thickness of the first electrode finger in the central region is less than the depth of the recess. The elastic wave apparatus according to claim 1.

3. The IDT electrode includes, in order from the piezoelectric side, a first layer, a second layer, and a third layer. The material of the second layer is different from the material of the third layer. The upper surface of the central region of the first electrode finger is formed by the third layer, The upper surface of the second edge region of the first electrode finger is formed by the second layer. The elastic wave apparatus according to claim 1.

4. The IDT electrode has, in order from the piezoelectric side, a lower layer and an upper layer with a lower density than the lower layer. The upper surface of the second edge region of the first electrode finger is formed by the upper layer. The elastic wave apparatus according to claim 1.

5. Let L be the length of the portion of the recess located within the second edge region in the direction in which the first electrode finger extends, let D be the depth of the recess, let dt be the amount by which the thickness of the first electrode finger in the second edge region is thinner than the thickness of the first electrode finger in the central region, and let P be dt / D × 100. 0% < P < 25%, and L and D are located in the range where FOM is 0.40 or greater in Figure 10 or Figure 11. P = 25%, and L and D are located in the range where FOM is 0.40 or higher in Figure 11. 25% < P < 50%, and L and D are located in the range where FOM is 0.40 or greater in Figure 11 or Figure 12. P = 50%, and L and D are located in the range where FOM is 0.40 or higher in Figure 12. 50% < P < 75%, and L and D are located in the range where FOM is 0.40 or greater in Figure 12 or Figure 13. P = 75%, and L and D are located in the range where FOM is 0.40 or higher in Figure 13. 75% < P < 100%, and L and D are located in the range where FOM is 0.40 or greater in Figure 13 or Figure 14, or P = 100%, and L and D are located in the range where FOM is 0.40 or higher in Figure 14. The elastic wave apparatus according to claim 1.

6. In the first electrode finger, the surface rising from the upper surface of the second edge region to the upper surface of the central region is inclined with respect to the normal of the first surface, with the upper surface being positioned closer to the central region. The elastic wave apparatus according to claim 1.

7. The thickness of the second busbar, at least on the side of the second edge region, is thinner than the thickness of the first electrode finger in the central region. The elastic wave apparatus according to claim 1.

8. A piezoelectric body having a first surface, An IDT electrode located on the first surface, It has, The IDT electrode is The first busbar and the second busbar are opposite each other, A plurality of first electrode fingers extending in parallel from the first busbar to the second busbar, It has a plurality of second electrode fingers that extend in parallel from the second busbar toward the first busbar and are positioned between the plurality of first electrode fingers, The intersection region where the first electrode finger and the second electrode finger overlap in the direction of elastic wave propagation is, A central region located on the central side in the opposing direction of the first busbar and the second busbar, A first edge region located on the side of the first busbar, It has a second edge region located on the side of the second busbar, The piezoelectric material has a recess between the first electrode finger and the second electrode finger in the second edge region. When the repeating interval between the plurality of first electrode fingers and the plurality of second electrode fingers is p, the length of the portion of the recess located within the second edge region in the direction in which the first electrode finger extends is L, and the depth of the recess is D, 0.50p ≤ L ≤ 2.50p, and 0.010p ≤ D ≤ 0.040p. Elastic wave device.

9. The thickness of the first electrode finger in the second edge region is the same as the thickness of the first electrode finger in the central region. 0.50p ≤ L ≤ 1.70p, and 0.010p ≤ D ≤ 0.040p, or 1.60p ≤ L ≤ 2.50p and 0.010p ≤ D ≤ 0.015p. The elastic wave apparatus according to claim 8.

10. The thickness of the second edge region of the first electrode finger is thinner than the thickness of the central region of the first electrode finger by a difference of more than 0% and less than or equal to 50% of the depth of the recess. 0.60p ≤ L ≤ 2.30p, and 0.013p ≤ D ≤ 0.036p. The elastic wave apparatus according to claim 8.

11. The thickness of the second edge region of the first electrode finger is thinner than the thickness of the central region of the first electrode finger by a difference of more than 50% but less than or equal to 100% of the depth of the recess. 0.85p ≤ L ≤ 2.50p, and 0.014p ≤ D ≤ 0.040p. The elastic wave apparatus according to claim 8.

12. Let dt be the amount by which the thickness of the second edge region of the first electrode finger is thinner than the thickness of the central region of the first electrode finger, and let P be dt / D × 100. P = 100%, and L and D are located in the range where FOM is 0.40 or higher in Figure 10. 0% < P < 25%, and L and D are located in the range where FOM is 0.40 or greater in Figure 10 or Figure 11. P = 25%, and L and D are located in the range where FOM is 0.40 or higher in Figure 11. 25% < P < 50%, and L and D are located in the range where FOM is 0.40 or greater in Figure 11 or Figure 12. P = 50%, and L and D are located in the range where FOM is 0.40 or higher in Figure 12. 50% < P < 75%, and L and D are located in the range where FOM is 0.40 or greater in Figure 12 or Figure 13. P = 75%, and L and D are located in the range where FOM is 0.40 or higher in Figure 13. 75% < P < 100%, and L and D are located in the range where FOM is 0.40 or greater in Figure 13 or Figure 14, or P = 100%, and L and D are located in the range where FOM is 0.40 or higher in Figure 14. The elastic wave apparatus according to claim 8.

13. The recess extends between the second edge region and the second busbar. The elastic wave apparatus according to claim 1 or 8.

14. The first electrode finger has a width in the second edge region that is narrower than the width in the central region. The elastic wave apparatus according to claim 1 or 8.

15. The first electrode finger has a width in the second edge region that is wider than the width in the central region. The elastic wave apparatus according to claim 1 or 8.

16. The side surface of the recess on the side of the central region is inclined with respect to the normal of the first surface, with the upper side being positioned closer to the central region. The elastic wave apparatus according to claim 1 or 8.

17. The first electrode finger is inclined such that the side surface in the second edge region is inclined such that the width of the first electrode finger becomes narrower towards the top compared to the side surface in the central region. The elastic wave apparatus according to claim 1 or 8.

18. Leaky waves or Rayleigh waves are used as the main components of elastic waves. The elastic wave apparatus according to claim 1 or 8.

19. On the second surface of the piezoelectric material, which is located opposite to the first surface, there is an intermediate layer with a lower sound velocity compared to the piezoelectric material. The intermediate layer further comprises a support substrate located on the opposite side of the piezoelectric element, and having a sound velocity faster than the piezoelectric element or the intermediate layer, When the repeating interval between the plurality of first electrode fingers and the plurality of second electrode fingers is p, the thickness of the piezoelectric body is 2p or less. The elastic wave apparatus according to claim 1 or 8.

20. The elastic wave apparatus according to claim 1 or 8, The antenna connected to the aforementioned elastic wave device, An IC connected to the antenna via the elastic wave device, A communication device that has the following features.

21. A method for manufacturing an elastic wave apparatus according to claim 1 or 8, The region of the first surface in which the recess is formed and the portion of the first electrode finger located in the second edge region are both etched. A method for manufacturing an elastic wave apparatus.

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