Elastic wave device and communication device

Abstract

The present invention improves the frequency characteristics of an elastic wave device. This elastic wave device comprises: a piezoelectric body that has a first surface; an IDT electrode that is positioned on the first surface and that has a plurality of electrode fingers which are separated from each other in a first direction; and a first electrode that is different from the IDT electrode. Each of the plurality of electrode fingers extends in a second direction intersecting the first direction. The piezoelectric body has a first end surface on one side in the first direction. The first electrode is located between the IDT electrode and the first end surface, extends in the second direction, and is electrically isolated from the IDT electrode.

Description

Acoustic wave devices and communication devices

[0001] The following disclosure relates to acoustic wave devices.

[0002] Patent Document 1 listed below discloses an example of the configuration of an elastic wave device.

[0003] Japanese Patent Application Publication No. 7-263998

[0004] An elastic wave device according to one aspect of the present disclosure includes a piezoelectric body having a first surface, an IDT electrode located on the first surface and having a plurality of electrode fingers spaced apart in a first direction, and a first electrode different from the IDT electrode, wherein each of the plurality of electrode fingers extends in a second direction intersecting the first direction, the piezoelectric body has a first end face on one side of the first direction, and the first electrode is located between the IDT electrode and the first end face in the first direction, extends in the second direction, and is electrically isolated from the IDT electrode.

[0005] 1 shows an example configuration of an elastic wave device according to embodiment 1. FIG. 1 shows an example configuration of an elastic wave device according to embodiment 1. FIG. 2 shows an example frequency characteristic of an elastic wave device as a comparative example. FIG. 3 shows an example frequency characteristic of an elastic wave device as an example. FIG. 4 shows the frequency characteristics of Comparative Example X and Example X. FIG. 5 shows an enlarged view of the graph of FIG. 5. FIG. 6 shows a further example frequency characteristic of an elastic wave device as an example. FIG. 7 shows a further example frequency characteristic of an elastic wave device as an example. FIG. 8 shows a further example frequency characteristic of an elastic wave device as an example. FIG. 9 shows an example relationship between distance D and the frequency characteristic of an elastic wave device. FIG. 10 shows an example configuration of an elastic wave device according to embodiment 2. FIG. 11 shows another example configuration of an elastic wave device according to embodiment 2. FIG. 12 shows another example configuration of an elastic wave device according to embodiment 2. FIG. 13 shows an example configuration of a communication device according to embodiment 3.

[0006] [Embodiment 1] Embodiment 1 will be described below. For convenience of explanation, components having the same functions as those described in Embodiment 1 will be denoted by the same reference numerals in the following embodiments, and their descriptions will not be repeated. For brevity, descriptions of well-known technical matters will be omitted as appropriate. Each component, material, and numerical value described in this specification is merely exemplary unless there is a contradiction in the content. Therefore, unless there is a contradiction in the content, for example, the positional relationship and connection relationship of each component are not limited to the examples in each figure. Furthermore, each figure is not necessarily drawn to scale. In this specification, unless there is a particular contradiction, the notation "A to B" for two numbers A and B means "greater than or equal to A and less than or equal to B."

[0007] 1 and 2 show an example of the configuration of an elastic wave device 1 according to a first embodiment. FIG. 1 shows a schematic front view of the layer structure of the elastic wave device 1. FIG. 2 shows a schematic plan view of the configuration of the elastic wave device 1. The elastic wave device 1 includes one or more elastic wave elements (also referred to as elastic wave resonators). For clarity of explanation, the first embodiment will be described assuming that the elastic wave device 1 includes a single elastic wave element.

[0008] For ease of explanation, this specification introduces a Cartesian coordinate system (D1-D2-D3 coordinate system) shown in Figures 1 and 2. The D1 direction in the example of embodiment 1 is the propagation direction of an elastic wave propagating within piezoelectric body 2 of elastic wave device 1. Embodiment 1 illustrates a case where multiple electrode fingers 32 in elastic wave device 1 are arranged in the D1 direction. The D1 direction may also be referred to as a first direction.

[0009] The D2 direction is an example of a direction that intersects with the D1 direction. In the example of embodiment 1, the electrode fingers 32 extend in the D2 direction. The D2 direction may also be referred to as the second direction. The D3 direction is the thickness direction of each part of the elastic wave device 1. In this specification, the positive direction of the D3 direction is described as the upward direction. Therefore, the negative direction of the D3 direction is the downward direction. The D3 direction may also be referred to as the third direction.

[0010] First, referring to FIG. 1 , an acoustic wave device 1 includes a piezoelectric body 2 and an IDT (Interdigital Transducer) electrode 3. The acoustic wave device 1 may include a support substrate (not shown) that supports each component of the acoustic wave device 1. The support substrate is located below the components. For example, the support substrate may be a Si substrate.

[0011] The piezoelectric body 2 has a first surface S1. In the first embodiment, the first surface S1 is a surface that supports the IDT electrode 3. The piezoelectric body 2 is made of, for example, a single crystal material. An example of the piezoelectric body 2 is lithium tantalate (LiTaO ３ :LT) or lithium niobate (LiNbO ３ In the first embodiment, the case where the piezoelectric body is LT will be mainly exemplified.

[0012] The IDT electrode 3 excites acoustic waves. For this reason, the IDT electrode 3 is also called an excitation electrode. The IDT electrode 3 has a plurality of electrode fingers 32. The electrode fingers 32 collectively refer to first electrode fingers 32 a and second electrode fingers 32 b, which will be described later.

[0013] In the example of embodiment 1, each of the multiple electrode fingers 32 is located on the first surface S1 of the piezoelectric body 2 and is spaced apart from one another in the direction D1. Specifically, each of the multiple electrode fingers 32 is located alternately and repeatedly on the first surface S1 at approximately constant intervals in the direction D1. In this specification, the pitch of the electrode fingers 32 is denoted as p. p is also referred to as the electrode finger pitch of the IDT electrode 3.

[0014] For example, p may be defined as the pitch (repetition interval) in the D1 direction between the centers of two adjacent electrode fingers 32. Therefore, p may be defined as the distance in the D1 direction between the center of one first electrode finger 32 a and the center of the second electrode finger 32 b adjacent to that first electrode finger 32 a.

[0015] As an example, p may be set equal to half the wavelength λ (λ / 2) of the acoustic wave excited by the IDT electrode 3. In this case, λ may be defined as twice the length of p. Therefore, in the first embodiment, a case where λ=2p is illustrated.

[0016] In this specification, the length of the electrode fingers 32 in the direction D1 is referred to as the width w of the electrode fingers 32. w may be set according to p. The ratio of w to p (w / p) is also referred to as the duty of the electrode fingers 32. Changing the duty can control the frequency characteristics of the acoustic wave device 1.

[0017] 2, the IDT electrode 3 may have a first bus bar 31a and a second bus bar 31b that face each other in the direction D2. In this specification, the first electrode finger 32a represents the electrode finger connected to the first bus bar 31a, and the second electrode finger 32b represents the electrode finger connected to the second bus bar 31b.

[0018] 2 , the first electrode finger 32a extends from the first bus bar 31a toward the second bus bar 31b. Meanwhile, the second electrode finger 32b extends from the second bus bar 31b toward the first bus bar 31a. Therefore, the elastic wave device 1 has an intersection region CR where the first electrode finger 32a and the second electrode finger 32b intersect in the D2 direction. The intersection region CR can also be expressed as a region where the multiple electrode fingers 32 overlap each other when viewed from the D1 direction.

[0019] In the Cartesian coordinate system of Figures 1 and 2, the positive direction of the D1 direction is defined as the right direction in the plane of the paper. In the example of embodiment 1, the piezoelectric body 2 has a first end face TM1 on one side in the D1 direction. In the example of Figures 1 and 2, the first end face TM1 is located on the side in the positive direction of the D1 direction (i.e., the right side in the plane of the paper). In the example of Figures 1 and 2, a first recess GV1 is formed in the piezoelectric body 2 on the side in the positive direction of the D1 direction.

[0020] For example, the first end surface TM1 may be defined by the first recess GV1. Therefore, the height of the first end surface TM1 may be determined as the depth of the first recess GV1. For example, the height of the first end surface TM1 may be set to 2p or more.

[0021] In the example of Embodiment 1, the elastic wave device 1 includes a first electrode 6a that is different from the IDT electrode 3. As shown in FIGS. 1 and 2 , the first electrode 6a is located between the IDT electrode 3 and the first end face TM1 in the direction D1. In the example of Embodiment 1, the first electrode 6a is located on the first surface S1. As shown in FIG. 2 , the first electrode 6a extends in the direction D2.

[0022] Furthermore, in the example of embodiment 1, the first electrode 6 a is electrically isolated from the IDT electrode 3. That is, the first electrode 6 a is not electrically connected to the IDT electrode 3. In the example of embodiment 1, the first electrode 6 a is not electrically connected to any other electrode. For this reason, the first electrode 6 a in embodiment 1 may be referred to as a first float electrode.

[0023] In the example of embodiment 1, the width of the first electrode 6a (i.e., the length of the first electrode 6a in the D1 direction) is constant at all positions in the D2 direction. Therefore, in the example of embodiment 1, the first electrode 6a has a uniform width in the region where the intersection region CR and the first electrode 6a overlap when viewed from the D1 direction.

[0024] In this specification, the width of the first electrode 6a is represented as WF. As shown in Figures 1 and 2, WF may be set to be larger than w. In this case, for example, the first electrode 6a can be easily manufactured.

[0025] 1, the side surface of the first electrode 6 a may be continuous with the first end surface TM1. For the sake of clarity, the first embodiment illustrates a case in which the position of the side surface of the first electrode 6 a coincides with the position of the first end surface TM1.

[0026] As described above, the first electrode 6a in the first embodiment is located closer to the first end face TM1 than the IDT electrode 3. Therefore, in the first embodiment, the distance between the first end face TM1 and the first electrode 6a in the direction D1 is smaller than the distance between the first end face TM1 and the IDT electrode 3. In the example of FIGS. 1 and 2, the distance between the first end face TM1 and the first electrode 6a is zero. The distance between the first end face TM1 and the IDT electrode 3 may be defined as the distance between the first end face TM1 and a target electrode finger, which will be described below.

[0027] In this specification, the electrode finger that is located closest to the first end face TM1 among the plurality of electrode fingers 32 is referred to as the target electrode finger. In the examples of Figures 1 and 2, this target electrode finger is indicated by the reference symbol 32t.

[0028] 1 and 2, in this specification, the distance in the D1 direction between the center of target electrode finger 32t and first end face TM1 is represented as D. As will be described later, D may be set to 2p to 2.35p, for example. Alternatively, D may be set to 2p to 2.15p.

[0029] The elastic wave device 1 may include a float electrode separate from the first electrode 6a. For example, as shown in FIGS. 1 and 2, the elastic wave device 1 may include a second electrode 6b separate from the IDT electrode 3 and the first electrode 6a. The second electrode 6b in the first embodiment is an example of a float electrode that pairs with the first electrode 6a. The second electrode 6b may be referred to as a second float electrode.

[0030] In this specification, the electrode finger located closest to the second end face TM2 among the plurality of electrode fingers 32 is referred to as the second target electrode finger. The second target electrode finger is an electrode finger that forms a pair with the above-mentioned target electrode finger 32t.

[0031] As shown in FIGS. 1 and 2, the piezoelectric body 2 may have a second end face TM2 on the other side in the D1 direction. In the example of FIGS. 1 and 2, the second end face TM2 is located on the negative side in the D1 direction (i.e., the left side in the plane of the drawing). In the example of FIGS. 1 and 2, a second recess GV2 is formed in the piezoelectric body 2 on the negative side in the D1 direction. The second recess GV2 is a recess that pairs with the above-mentioned first recess GV1. Therefore, for example, the second end face TM2 may be defined by the second recess GV2. The height of the second end face TM2 may be determined as the depth of the second recess GV2.

[0032] 1 and 2 illustrate, for clarity of explanation, a case in which the second recess GV2 has the same dimensions as the first recess GV1 and the second electrode 6b has the same dimensions as the first electrode 6a. Therefore, in the example of embodiment 1, the width of the second electrode 6b is equal to WF. The distance in direction D1 between the center of the second target electrode finger and the second end face TM2 is equal to D. However, in one aspect of the present disclosure, the second recess GV2 may have a different dimension from the first recess GV1, and the second electrode 6b may have a different dimension from the first electrode 6a.

[0033] 1 and 2, the second electrode 6b is located between the IDT electrode 3 and the second end face TM2 in the direction D1. In the example of the first embodiment, the second electrode 6b is also located on the first surface S1. As shown in FIG. 2, the second electrode 6b extends in the direction D2.

[0034] Furthermore, in the example of embodiment 1, the second electrode 6b is electrically isolated from the IDT electrode 3. That is, the second electrode 6b is not electrically connected to the IDT electrode 3. In the example of embodiment 1, the second electrode 6b is not electrically connected to any other electrode.

[0035] (Example of Study Results on Frequency Characteristics of Elastic Wave Device 1) For example, it is believed that the design conditions of first electrode 6a affect the frequency characteristics of elastic wave device 1. Therefore, by selecting appropriate design conditions for first electrode 6a, there is room for improving the frequency characteristics of elastic wave device 1. Therefore, the inventor of the present application (hereinafter abbreviated as "the inventor") conducted a simulation to study the relationship between the design conditions of first electrode 6a and the frequency characteristics of elastic wave device 1.

[0036] The simulation conditions in the first embodiment are as follows: Material of the piezoelectric body 2: LT p = 1 μm Number of electrode fingers 32: 150 Duty = 0.50 Height of the first end face TM1: 2 μm Width of the first recess GV1: 1 μm In this way, in the simulation, w is set to 0.5p, the height of the first end face TM1 is set to 2p, and the width of the first recess GV1 is set to p.

[0037] In a simulation, the inventors varied the above-described D and WF and derived the frequency characteristics of the acoustic wave device (in this example, the acoustic wave element) for each combination of D and WF. Figures 3 and 4 show examples of the simulation results derived by the inventors.

[0038] 3 and 4, the dotted line represents the phase characteristics of the elastic wave device, and the solid line represents the impedance characteristics of elastic wave device 1. In the graphs of FIGS. 3 and 4, the horizontal axis represents frequency. The left vertical axis represents the absolute value (magnitude) of the impedance of elastic wave device 1. In this specification, the absolute value of impedance will be abbreviated as impedance unless there is a contradiction in content.

[0039] In the graphs of Figures 3 and 4, the right vertical axis represents the phase of the impedance of the elastic wave device. In this specification, the maximum value of this phase is referred to as "MaxPhase." MaxPhase can be used as an index value that indicates the quality of the frequency characteristics of the elastic wave device. The theoretical maximum value of MaxPhase is 90°. Therefore, the closer MaxPhase is to 90°, the better the frequency characteristics of the elastic wave device can be said to be. Specifically, the closer MaxPhase is to 90°, the smaller the loss in the elastic wave device can be said to be.

[0040] 3 and 4, D and W are shown as values ​​normalized by p. For example, the notation "D=2.01, WF=1.26" in the example of FIG. 3 means that "D is 2.01p and WF is 1.26p."

[0041] In the example of Fig. 3, unlike the example of Fig. 4 described below, a simulation is performed for the case where the first electrode 6a is electrically connected to the IDT electrode 3. Therefore, the example of Fig. 3 is positioned as a comparative example for the example of Fig. 4. In the example of Fig. 3, unlike the example of Fig. 4, the second electrode 6b is also electrically connected to the IDT electrode 3.

[0042] In the example of Figure 3, the frequency characteristics of the comparative elastic wave device are shown for each of five combinations of D and W: D = 2.01, WF = 1.26 D = 2.02, WF = 1.27 D = 2.03, WF = 1.28 D = 2.04, WF = 1.29 D = 2.05, WF = 1.30

[0043] In the example of FIG. 3 , of the five frequency characteristics, the frequency characteristic when "D = 2.03, WF = 1.28" is the best. Hereinafter, the case of "D = 2.03, WF = 1.28" in FIG. 3 will be referred to as Comparative Example X. Specifically, of the five examples shown in FIG. 3 , Comparative Example X has the highest MaxPhase. Furthermore, of the five examples, Comparative Example X has the smallest spurious in the low-frequency and high-frequency regions.

[0044] 4, unlike the example of FIG. 3 described above, a simulation is performed for the case where the first electrode 6a is electrically isolated from the IDT electrode 3. Therefore, the example of FIG. 4 corresponds to an example of embodiment 1. In the example of FIG. 4, the second electrode 6b is also electrically isolated from the IDT electrode 3.

[0045] In the example of Figure 4, the frequency characteristics of the elastic wave device 1 are shown for each of five combinations of D and W: D = 2.04, WF = 1.29 D = 2.05, WF = 1.30 D = 2.06, WF = 1.31 D = 2.07, WF = 1.32 D = 2.08, WF = 1.33

[0046] In the example of Fig. 4, of the five frequency characteristics, the frequency characteristic when "D = 2.06, WF = 1.31" is the best. Hereinafter, the case of "D = 2.06, WF = 1.31" in Fig. 4 will be referred to as Example X. Specifically, of the five examples shown in Fig. 4, Example X has the highest MaxPhase. Furthermore, of the five examples, Example X has the smallest spurious in the low-frequency and high-frequency regions.

[0047] The inventors further compared the frequency characteristics of Comparative Example X and Example X. FIG. 5 shows the frequency characteristics of Comparative Example X and Example X. In FIG. 5, reference numeral 510 indicates the impedance characteristics of Comparative Example X and Example X, and reference numeral 520 indicates the phase characteristics of Comparative Example X and Example X. In the example of FIG. 5, Comparative Example X is indicated by a dotted line, and Example X is indicated by a solid line.

[0048] Fig. 6 shows enlarged views of each graph in Fig. 5. In Fig. 6, reference numeral 610 indicates an enlarged view of the graph indicated by reference numeral 510 near the resonant frequency. The resonant frequency is defined as the frequency at which the impedance of the elastic wave device 1 is minimum. As indicated by reference numeral 610, the minimum impedance value in Example X is smaller than the minimum impedance value in Comparative Example X. This indicates that Example X has smaller loss than Comparative Example X.

[0049] 6, reference numeral 620 denotes an enlarged view of the graph of reference numeral 520 near the resonant frequency. As shown by reference numeral 620, MaxPhase in Example X is larger than MaxPhase in Comparative Example X. This also indicates that Example X has smaller loss than Comparative Example X. Reference numeral 630 denotes an enlarged view of the graph of reference numeral 520 near a frequency slightly lower than the resonant frequency.

[0050] As described above, the inventors have confirmed through simulations that the frequency characteristics of the acoustic wave device 1 can be improved by electrically isolating the first electrode 6 a from the IDT electrode 3 .

[0051] (Further Example of Study Results on Frequency Characteristics of Elastic Wave Device 1) Next, the inventors conducted further simulation studies on the frequency characteristics of the elastic wave device 1 in which the first electrode 6 a is electrically isolated from the IDT electrode 3. Specifically, the inventors derived the frequency characteristics of the elastic wave device 1 for each of further combinations of D and W in the elastic wave device 1.

[0052] 7 to 9 show examples of simulation results derived by the inventors. In the graphs of FIGS. 7 to 9, as in the examples of FIGS. 3 and 4 described above, the dotted line represents the phase characteristics of the elastic wave device 1, and the solid line represents the impedance characteristics of the elastic wave device 1. The left vertical axis represents the absolute value of the impedance of the elastic wave device 1, and the right vertical axis represents the phase of the impedance of the elastic wave device 1. In the examples of FIGS. 7 to 9, D and W are also shown as values ​​normalized by p.

[0053] In the example of Figure 7, the frequency characteristics of the elastic wave device 1 are shown for each of the eight combinations of D and W: D = 1.60, WF = 0.85 D = 1.65, WF = 0.90 D = 1.70, WF = 0.95 D = 1.75, WF = 1.00 D = 1.80, WF = 1.05 D = 1.85, WF = 1.10 D = 1.90, WF = 1.15 D = 1.95, WF = 1.20

[0054] In the example of Figure 8, the frequency characteristics of the elastic wave device 1 are shown for each of the eight combinations of D and W: D = 2.00, WF = 1.25 D = 2.05, WF = 1.30 D = 2.10, WF = 1.35 D = 2.15, WF = 1.40 D = 2.20, WF = 1.45 D = 2.25, WF = 1.50 D = 2.30, WF = 1.55 D = 2.35, WF = 1.60

[0055] In the example of Figure 9, the frequency characteristics of the elastic wave device 1 are shown for each of three combinations of D and W: D = 2.40, WF = 1.65, D = 2.45, WF = 1.70, and D = 2.50, WF = 1.75.

[0056] 7 to 9, the frequency characteristics of elastic wave device 1 can vary depending on D and W. Therefore, the inventors further studied the relationship between D and the frequency characteristics of elastic wave device 1.

[0057] Fig. 10 shows an example of the relationship between D and the frequency characteristics of the elastic wave device 1. In Fig. 10, reference numeral 1010 indicates the relationship between D and MaxPhase in the examples of Figs. 7 to 9. In the example of Fig. 10, D is also shown as a value normalized by p. In the graph indicated by reference numeral 1010, the horizontal axis represents D, and the vertical axis represents MaxPhase.

[0058] 10, reference numeral 1020 indicates the relationship between D and Qa in the examples of FIGS. 7 to 9. Qa represents the Q value at the anti-resonance frequency of elastic wave device 1. The anti-resonance frequency of elastic wave device 1 is defined as the frequency at which the impedance of elastic wave device 1 is maximized. In the graph of reference numeral 1020, the horizontal axis represents D and the vertical axis represents Qa. It can be said that the higher the Qa, the better the frequency characteristics of elastic wave device 1.

[0059] As shown in the graph with reference numeral 1010, when D is 2 to 2.35 (corresponding to the case shown in FIG. 8 above), a high MaxPhase is obtained. Specifically, when D is 2 to 2.35, MaxPhase is 89.5° or greater. In addition, as shown in the graph with reference numeral 1020, when D is 2 to 2.35, a high Qa is obtained. Specifically, when D is 2 to 2.35, Qa exceeds 1500.

[0060] Referring again to Figure 8, among the eight examples shown in Figure 8, the following four examples provide particularly good frequency characteristics: D = 2.00, WF = 1.25; D = 2.05, WF = 1.30; D = 2.10, WF = 1.35; and D = 2.15, WF = 1.40. Specifically, in these four examples, the maximum value of the phase spurious in the frequency range below the resonant frequency is less than 60°.

[0061] As described above, for example, by setting D to 2p to 2.35p, good frequency characteristics can be obtained, and by setting D to 2p to 2.15p, even better frequency characteristics can be obtained.

[0062] [Embodiment 2] In Embodiment 2, various configuration examples of elastic wave devices according to one aspect of the present disclosure will be described. Various configuration examples of elastic wave devices according to Embodiment 2 will be described below with reference to Fig. 11 to Fig. 14. Fig. 11 to Fig. 14 are all counterparts to Fig. 2 described above.

[0063] (1) FIG. 11 illustrates a configuration example of an elastic wave device according to Embodiment 2. The elastic wave device in the example of FIG. 11 is referred to as elastic wave device 1A. Unlike the example of FIG. 2, the example of FIG. 11 illustrates a non-zero distance between the first end surface TM1 and the first electrode 6a. In this manner, the first electrode 6a may be spaced apart from the first end surface TM1. As illustrated in FIG. 11, the second electrode 6b may also be spaced apart from the second end surface TM2.

[0064] (2) Fig. 12 shows another example configuration of the elastic wave device according to the second embodiment. The elastic wave device in the example shown in Fig. 12 is referred to as elastic wave device 1B. As shown in Fig. 12, elastic wave device 1B includes a first reflector 4a located between the IDT electrode 3 and the first electrode 6a in the direction D1. The first reflector 4a may be configured to reflect a portion of the elastic wave arriving from the IDT electrode 3.

[0065] 12 , elastic wave device 1B may include second reflector 4b located between IDT electrode 3 and second electrode 6b in direction D1. Second reflector 4b is a reflector that pairs with first reflector 4a. By providing at least one reflector in this manner, the frequency characteristics of the elastic wave device can be further adjusted.

[0066] (3) Fig. 13 shows yet another example configuration of the elastic wave device according to Embodiment 2. The elastic wave device in the example shown in Fig. 13 is referred to as elastic wave device 1C. In the example shown in Fig. 13, unlike the example shown in Fig. 2, first electrode 6a is grounded.

[0067] Therefore, the elastic wave device 1C may include, for example, a first ground pattern GP1. The first ground pattern GP1 may be grounded by any method. In the example of Fig. 13, the first electrode 6a is electrically connected to the first ground pattern GP1. In this manner, the first electrode 6a in the example of Fig. 13 is grounded via the first ground pattern GP1.

[0068] In the example of Fig. 13 , the second electrode 6b may also be grounded. Therefore, the elastic wave device 1C may include a second ground pattern GP2. The second ground pattern GP2 is a ground pattern that pairs with the first ground pattern GP1. In the example of Fig. 13 , the second electrode 6b is electrically connected to the second ground pattern GP2. In this way, the second electrode 6b in the example of Fig. 13 is grounded via the second ground pattern GP2.

[0069] As described above, the first electrode 6 a and the second electrode 6 b in one aspect of the present disclosure only need to be electrically isolated from the IDT electrode 3 , and do not necessarily have to be floating electrodes.

[0070] (4) FIG. 14 illustrates yet another exemplary configuration of the elastic wave device according to Embodiment 2. The elastic wave device in the example of FIG. 14 is referred to as elastic wave device 1D. As shown in FIG. 14 , elastic wave device 1D includes a non-floating electrode 5 instead of second electrode 6b. In the example of FIG. 14 , non-floating electrode 5 extends from second bus bar 31b toward first bus bar 31a. Therefore, unlike second electrode 6b in the example of FIG. 2 , non-floating electrode 5 is electrically connected to IDT electrode 3.

[0071] As such, an acoustic wave device according to one aspect of the present disclosure does not necessarily have a pair of electrodes (e.g., first electrode 6 a and second electrode 6 b) that are electrically isolated from the IDT electrode 3. The acoustic wave device may have a first electrode 6 a that is electrically isolated from the IDT electrode 3 between the IDT electrode 3 and the first end face TM1.

[0072] 14 , the width of the non-float electrode 5 is smaller than the width w of the electrode fingers 32. However, the width of the non-float electrode 5 is not limited to this example. For example, the width of the non-float electrode 5 may be the same as w. Alternatively, the width of the non-float electrode 5 may be larger than w. Therefore, as an example, the width of the non-float electrode 5 may be the same as the width WF of the first electrode 6a. By changing the width of the non-float electrode 5, the frequency characteristics of the elastic wave device 1D can be further adjusted.

[0073] (5) An acoustic wave device according to an aspect of the present disclosure may have a laminated structure in which a layer of another material that is thinner than the piezoelectric body 2 is laminated to the piezoelectric body 2. An example of the other material is Si.

[0074] In this specification, for example, a layer structure in which the IDT electrode 3, the piezoelectric body 2, and Si are arranged in this order from the top is referred to as "IDT / piezoelectric body / Si." As described above, the material of the piezoelectric body 2 may be, for example, LT. Therefore, an acoustic wave device according to one aspect of the present disclosure may have a layer structure of "IDT / LT / Si."

[0075] As another example, an acoustic wave device according to an aspect of the present disclosure may include a low acoustic velocity layer between the piezoelectric body 2 and Si. Examples of materials for the low acoustic velocity layer include SiO. ２ Therefore, an acoustic wave device according to an aspect of the present disclosure may be, for example, an "IDT / LT / SiO ２ / Si" layer structure.

[0076] As yet another example, an acoustic wave device according to an aspect of the present disclosure may have a laminated structure of a low acoustic impedance layer and a high acoustic impedance layer between the piezoelectric body 2 and Si. In this specification, a multilayer reflective film in which one low acoustic impedance layer and one high acoustic impedance layer are alternately laminated is referred to as a [low acoustic impedance layer / high acoustic impedance layer].

[0077] Examples of materials for the low acoustic impedance layer include SiO ２ Examples of materials for the high acoustic impedance layer include HfO ２ Therefore, the layer structure of the above-mentioned multilayer reflective film can be, for example, [SiO ２ / HfO ２ ].

[0078] The laminated structure of the low acoustic impedance layer and the high acoustic impedance layer may be formed by a plurality of multilayer reflective films. For example, the laminated structure may be formed by four multilayer reflective films. Therefore, an acoustic wave device according to one aspect of the present disclosure may be formed by, for example, an "IDT / LT / [SiO ２ / HfO ２ ]×4 / Si”.

[0079] 15 illustrates a configuration example of a communication device 151 according to a third embodiment. The communication device 151 performs wireless communication using radio waves. The communication device 151 may include an elastic wave device according to an aspect of the present disclosure (e.g., the elastic wave device 1). For example, the transmission filter 109T and the reception filter 111R in FIG. 15 may each include the elastic wave device 1 as a frequency filter.

[0080] In the communication device 151, a transmission information signal TIS containing information to be transmitted may be modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency-Integrated Circuit) 153, and converted into a transmission signal TS. A bandpass filter 155 may remove unnecessary components from the TS outside the transmission passband. Next, the TS after removing the unnecessary components may be amplified by an amplifier 157 and then input to a transmission filter 109T.

[0081] The transmission filter 109T may remove unnecessary components outside the transmission passband from the transmission signal TS input via the transmission terminal. The transmission filter 109T may output the TS after removing the unnecessary components to the antenna 159 via the antenna terminal ANT. The antenna 159 can convert the TS, which is an electrical signal input to itself, into radio waves as a wireless signal and transmit the radio waves to the outside of the communication device 151.

[0082] The antenna 159 can also convert received external radio waves into a received signal RS, which is an electrical signal. The antenna 159 may input the RS to the receive filter 111R via the antenna terminal ANT. The receive filter 111R may remove unnecessary components outside the receive passband from the input RS. The receive filter 111R may output the received signal RS after the unnecessary components have been removed to the amplifier 161 via the receive terminal. The output RS may be amplified by the amplifier 161. The bandpass filter 163 may remove unnecessary components outside the receive passband from the amplified RS. The RS after the unnecessary components have been removed may be frequency-downshifted and demodulated by the RF-IC 153, and converted into a received information signal RIS.

[0083] The TIS and RIS may be low-frequency signals (baseband signals) containing appropriate information. For example, the TIS and RIS may be analog or digitized audio signals. The passband of the radio signals may be set appropriately and may comply with any of various standards.

[0084] [Summary] An elastic wave device according to aspect 1 of the present disclosure includes a piezoelectric body having a first surface, an IDT electrode located on the first surface and having a plurality of electrode fingers spaced apart in a first direction, and a first electrode different from the IDT electrode, wherein each of the plurality of electrode fingers extends in a second direction intersecting the first direction, the piezoelectric body has a first end face on one side of the first direction, and the first electrode is located between the IDT electrode and the first end face in the first direction, extends in the second direction, and is electrically isolated from the IDT electrode.

[0085] In an elastic wave device according to aspect 2 of the present disclosure, in aspect 1, the IDT electrode may have an intersection region in which each of the plurality of electrode fingers overlaps when viewed from the first direction, and the first electrode may have a uniform width in the range in which the intersection region and the first electrode overlap when viewed from the first direction.

[0086] In an elastic wave device according to a third aspect of the present disclosure, in addition to the first or second aspect, the width of the first electrode may be greater than the width of each of the plurality of electrode fingers.

[0087] An elastic wave device according to aspect 4 of the present disclosure may be any one of aspects 1 to 3, and may further include a second electrode different from the IDT electrode and the first electrode, the piezoelectric body may have a second end face on the other side of the first direction, and the second electrode may be located between the IDT electrode and the second end face in the first direction, extend in the second direction, and be electrically isolated from the IDT electrode.

[0088] In an elastic wave device according to aspect 5 of the present disclosure, in any one of aspects 1 to 4, the distance between the first end face and the first electrode in the first direction may be smaller than the distance between the first end face and the IDT electrode.

[0089] In an elastic wave device according to a sixth aspect of the present disclosure, in any one of the first to fifth aspects, a side surface of the first electrode may be continuous with the first end surface.

[0090] In an elastic wave device according to a seventh aspect of the present disclosure, in any one of the first to sixth aspects, the first electrode may be grounded.

[0091] In an elastic wave device according to aspect 8 of the present disclosure, in any one of aspects 1 to 7, when the pitch of the plurality of electrode fingers in the first direction is denoted as p and the electrode finger among the plurality of electrode fingers that is located closest to the first end face is referred to as the target electrode finger, the distance in the first direction between the center of the target electrode finger and the first end face may be 2p or more and 2.35p or less.

[0092] According to a ninth aspect of the present disclosure, in the elastic wave device of the eighth aspect, the distance between the center of the target electrode finger in the first direction and the first end face may be equal to or greater than 2p and equal to or less than 2.15p.

[0093] An elastic wave device according to a tenth aspect of the present disclosure is any one of the first to ninth aspects, and may further include a first reflector positioned between the IDT electrode and the first electrode in the first direction.

[0094] In an elastic wave device according to aspect 11 of the present disclosure, when the pitch of the electrode fingers in the first direction in any one of aspects 1 to 10 is denoted as p, the height of the first end face may be 2p or more.

[0095] In the elastic wave device according to Aspect 12 of the present disclosure, in any one of Aspects 1 to 11, the material of the piezoelectric body may be LT or LN.

[0096] A communication device according to a thirteenth aspect of the present disclosure may include the acoustic wave device according to any one of the first to twelfth aspects.

[0097] [Additional Notes] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art could easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0098] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D Acoustic wave device 2 Piezoelectric body 3 IDT electrode 4a First reflector 6a First electrode 6b Second electrode 32 Electrode finger 32t Target electrode finger 151 Communication device S1 First surface TM1 First end surface TM2 Second end surface CR Intersection region

Claims

1. An elastic wave device comprising: a piezoelectric body having a first surface; an IDT electrode located on the first surface and having a plurality of electrode fingers spaced apart in a first direction; and a first electrode different from the IDT electrode, wherein each of the plurality of electrode fingers extends in a second direction intersecting the first direction; the piezoelectric body having a first end face on one side of the first direction; and the first electrode located between the IDT electrode and the first end face in the first direction, extending in the second direction, and being electrically isolated from the IDT electrode.

2. The elastic wave device according to claim 1, wherein the IDT electrode has an intersection region where each of the plurality of electrode fingers overlaps when viewed from the first direction, and the first electrode has a uniform width in the area where the intersection region and the first electrode overlap when viewed from the first direction.

3. The acoustic wave device according to claim 1, wherein the width of the first electrode is greater than the width of each of the plurality of electrode fingers.

4. The elastic wave device according to any one of claims 1 to 3, wherein the elastic wave device comprises a second electrode different from the IDT electrode and the first electrode, the piezoelectric body has a second end face on the other side of the first direction, and the second electrode is located between the IDT electrode and the second end face in the first direction, extends in the second direction, and is electrically isolated from the IDT electrode.

5. An elastic wave device according to claim 1, wherein the distance between the first end face and the first electrode in the first direction is smaller than the distance between the first end face and the IDT electrode.

6. The acoustic wave device according to claim 1, wherein a side surface of the first electrode is continuous with the first end surface.

7. The acoustic wave device according to claim 1, wherein the first electrode is grounded.

8. An elastic wave device according to any one of claims 1 to 7, wherein the pitch of the plurality of electrode fingers in the first direction is denoted by p, and the electrode finger among the plurality of electrode fingers that is located closest to the first end face is referred to as the target electrode finger, and the distance in the first direction between the center of the target electrode finger and the first end face is 2p or more and 2.35p or less.

9. The acoustic wave device according to claim 8, wherein the distance in the first direction between the center of the target electrode finger and the first end face is not less than 2p and not more than 2.15p.

10. The acoustic wave device according to claim 1, further comprising a first reflector positioned between the IDT electrode and the first electrode in the first direction.

11. The elastic wave device according to claim 1, wherein, when the pitch of the plurality of electrode fingers in the first direction is denoted as p, the height of the first end face is 2p or more.

12. The acoustic wave device according to claim 1, wherein the piezoelectric material is LT or LN.

13. A communication device comprising the acoustic wave device according to any one of claims 1 to 12.

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