Elastic wave device

Abstract

The present invention suppresses fluctuations in frequency characteristics. The piezoelectric device includes: a piezoelectric layer having a first main surface and a second main surface facing each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes. The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component in a surface layer. The insulating film of the first component has higher moisture resistance than the insulating film of the second component. The insulating film of the second component has higher plasma resistance than the insulating film of the first component.

Description

Technical Field

[0001] The present disclosure relates to elastic wave devices. Background Art

[0002] Patent Document 1 describes an elastic wave device.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-257019 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the elastic wave device disclosed in Patent Document 1, a protective film may be laminated on the functional electrode to obtain desired frequency characteristics. In this case, the frequency characteristics may change due to moisture absorption of the protective film or deterioration of the protective film due to exposure to plasma in the manufacturing process of the elastic wave device.

[0008] The present disclosure is to solve the above-mentioned problems, and an object of the present disclosure is to suppress the variation in frequency characteristics.

[0009] Means for solving problems

[0010] An elastic wave device involved in one embodiment comprises: a piezoelectric layer, which has a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes, which are arranged on at least one of the first main surface and the second main surface; and a protective film, which covers at least a portion of the pair of electrodes, the protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component has higher moisture resistance than the insulating film of the second component, and the insulating film of the second component has higher plasma resistance than the insulating film of the first component.

[0011] The elastic wave device involved in other embodiments comprises: a piezoelectric layer, which has a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes, which are arranged on at least one of the first main surface and the second main surface; and a protective film, which covers at least a portion of the pair of electrodes, the protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon nitride oxide film.

[0012] The elastic wave device involved in other embodiments comprises: a piezoelectric layer having a first principal surface and a second principal surface opposite to each other in a first direction; at least one pair of electrodes arranged on at least one of the first principal surface and the second principal surface; and a protective film covering at least a portion of the pair of electrodes, the protective film including an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon oxide film.

[0013] The elastic wave device involved in other embodiments comprises: a piezoelectric layer, which has a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes, which are arranged on at least any one of the first main surface and the second main surface; and a protective film, which covers at least a portion of the pair of electrodes, the protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component and the insulating film of the second component are silicon nitride oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0014] The elastic wave device involved in other embodiments comprises: a piezoelectric layer, which has a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes, which are arranged on at least one of the first main surface and the second main surface; and a protective film, which covers at least a portion of the pair of electrodes, the protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component is a silicon nitride oxide film, and the insulating film of the second component is a silicon oxide film.

[0015] The elastic wave device involved in other embodiments comprises: a piezoelectric layer, which has a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes, which are arranged on at least any one of the first main surface and the second main surface; and a protective film, which covers at least a portion of the pair of electrodes, the protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component and the insulating film of the second component are aluminum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0016] The elastic wave device involved in other embodiments comprises: a piezoelectric layer, which has a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes, which are arranged on at least any one of the first main surface and the second main surface; and a protective film, which covers at least a portion of the pair of electrodes, the protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component and the insulating film of the second component are titanium oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0017] The elastic wave device involved in other embodiments comprises: a piezoelectric layer having a first main surface and a second main surface opposite to each other in a first direction; at least one pair of electrodes arranged on at least any one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, the protective film including an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface, the insulating film of the first component and the insulating film of the second component are tantalum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0018] Effects of the Invention

[0019] According to the present disclosure, it is possible to suppress the variation in frequency characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A It is a perspective view showing the elastic wave device according to the first embodiment.

[0021] Figure 1B It is a plan view showing the electrode structure of the first embodiment.

[0022] Figure 2 It is along Figure 1A A partial cross-sectional view of line II-II.

[0023] Figure 3A It is a schematic cross-sectional view for explaining Lamb waves propagating through the piezoelectric layer of the comparative example.

[0024] Figure 3B Schematic cross-sectional view for explaining a bulk wave of a thickness shear first-order mode propagating through the piezoelectric layer in the first embodiment.

[0025] Figure 4 Schematic cross-sectional view for explaining the amplitude direction of a bulk wave of a thickness shear first-order mode propagating through the piezoelectric layer in the first embodiment.

[0026] Figure 5 It is an explanatory diagram showing an example of the resonance characteristics of the elastic wave device according to the first embodiment.

[0027] Figure 6 This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average distance between the centers of adjacent electrodes is set to p and the average thickness of the piezoelectric layer is set to d in the elastic wave device of the first embodiment.

[0028] Figure 7 This is a schematic plan view showing an example in which a pair of electrodes is provided in the elastic wave device according to the first embodiment.

[0029] Figure 8 This is a reference diagram showing an example of the resonance characteristics of the elastic wave device according to the first embodiment.

[0030] Fig. 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the impedance of the spurious normalized by 180 degrees, which is the magnitude of the spurious, when the elastic wave device according to the first embodiment is configured with a large number of elastic wave resonators.

[0031] Fig.10 It is an explanatory diagram showing the relationship among d / 2p, metallization ratio MR, and relative bandwidth.

[0032] Fig.11 This is an explanatory diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible.

[0033] Fig.12 This is a partially cutaway perspective view for explaining an elastic wave device according to an embodiment of the present disclosure.

[0034] Fig.13 This is a schematic plan view showing an example of the elastic wave device according to the first embodiment.

[0035] Fig.14 It is along Fig.13 A cross-sectional view of line XIV-XIV.

[0036] Fig.15 It is along Fig.13 A cross-sectional view of line XV-XV.

[0037] Fig.16 yes Fig.14 An enlarged cross-sectional view of area E.

[0038] Fig.17 This is a schematic cross-sectional view for explaining a sacrificial layer forming step in the method for manufacturing the elastic wave device according to the first embodiment.

[0039] Fig.18This is a schematic cross-sectional view for explaining the intermediate layer forming step in the method for manufacturing the elastic wave device according to the first embodiment.

[0040] Fig.19 This is a schematic cross-sectional view for explaining a bonding step in the method for manufacturing the elastic wave device according to the first embodiment.

[0041] Fig. 20 This is a schematic cross-sectional view for explaining a thinning step in the method for manufacturing the elastic wave device according to the first embodiment.

[0042] Fig.21 This is a schematic cross-sectional view for explaining an electrode forming step in the method for manufacturing the elastic wave device according to the first embodiment.

[0043] Fig. 22 This is a schematic cross-sectional view for explaining a step of forming an insulating film of a first component in the method for manufacturing the elastic wave device according to the first embodiment.

[0044] Fig.23 This is a schematic cross-sectional view for explaining the step of forming the insulating film of the second component in the method for manufacturing the elastic wave device according to the first embodiment.

[0045] Fig.24 This is a schematic cross-sectional view for explaining a through-hole forming step in the method for manufacturing the elastic wave device according to the first embodiment.

[0046] Fig.25 This is a schematic cross-sectional view for explaining an etching step in the method for manufacturing the elastic wave device according to the first embodiment.

[0047] Fig.26 This is a schematic cross-sectional view showing an example of an elastic wave device according to the second embodiment. DETAILED DESCRIPTION

[0048] Hereinafter, the embodiments of the present disclosure are described in detail based on the accompanying drawings. In addition, the present disclosure is not limited by the embodiments. In addition, the various embodiments described in the present disclosure are illustrative contents, and partial replacement or combination of structures can be performed between different embodiments. After the modified example and the second embodiment, the description of matters common to the first embodiment is omitted, and only the differences are described. In particular, the same effects produced by the same structure are not mentioned one by one in each embodiment.

[0049] (First embodiment)

[0050] Figure 1A It is a perspective view showing the elastic wave device according to the first embodiment. Figure 1BIt is a plan view showing the electrode structure of the first embodiment.

[0051] The elastic wave device 1 of the first embodiment has a piezoelectric layer 2 including LiNbO3. The piezoelectric layer 2 may also include LiTaO3. The cutting angle of LiNbO3 and LiTaO3 is Z-cut in the first embodiment. The cutting angle of LiNbO3 and LiTaO3 may also be a rotated Y-cut or an X-cut. Preferably, the propagation direction of Y propagation and X propagation is ±30°.

[0052] The thickness of the piezoelectric layer 2 is not particularly limited, but is preferably 50 nm to 1000 nm in order to effectively excite the thickness shear first-order mode. In addition, the electrode fingers 3 and 4 may be provided on the second main surface 2 b.

[0053] The piezoelectric layer 2 has a first main surface 2a and a second main surface 2b that are opposed to each other in the Z direction. The electrode fingers 3 and the electrode fingers 4 are provided on the first main surface 2a.

[0054] Here, electrode finger 3 is an example of a "first electrode finger", and electrode finger 4 is an example of a "second electrode finger". Figure 1A and Figure 1B In the figure, the plurality of electrode fingers 3 are a plurality of "first electrode fingers" connected to the first bus bar 5. The plurality of electrode fingers 4 are a plurality of "second electrode fingers" connected to the second bus bar 6. The plurality of electrode fingers 3 and the plurality of electrode fingers 4 are interlaced with each other. Thus, an IDT (Interdigital Transducer) electrode having electrode fingers 3, electrode fingers 4, first bus bar 5, and second bus bar 6 is formed.

[0055] The electrode finger 3 and the electrode finger 4 have a rectangular shape and have a length direction. In a direction orthogonal to the length direction, the electrode finger 3 is opposed to the electrode finger 4 adjacent to the electrode finger 3. The length direction of the electrode fingers 3 and 4 and the direction orthogonal to the length direction of the electrode fingers 3 and 4 are directions intersecting the thickness direction of the piezoelectric layer 2. Therefore, the electrode finger 3 and the electrode finger 4 adjacent to the electrode finger 3 can also be said to be opposed in a direction intersecting the thickness direction of the piezoelectric layer 2. In the following description, the thickness direction of the piezoelectric layer 2 is sometimes set as the Z direction (or the first direction), the length direction of the electrode fingers 3 and the electrode fingers 4 is set as the Y direction (or the second direction), and the direction orthogonal to the electrode fingers 3 and the electrode fingers 4 is set as the X direction (or the third direction) for description.

[0056] In addition, the length direction of electrode finger 3 and electrode finger 4 can also be replaced with Figure 1A and Figure 1B The length direction of the electrode fingers 3 and 4 shown in the figure is perpendicular to each other. Figure 1A and Figure 1B In this case, the first bus bar 5 and the second bus bar 6 extend in the direction in which the first bus bar 5 and the second bus bar 6 extend. Figure 1A and Figure 1B The electrode fingers 3 and 4 extend in the direction in which the electrode fingers 3 and 4 extend. In addition, a plurality of pairs of adjacent electrode fingers 3 connected to one potential and electrode fingers 4 connected to another potential are provided in a direction orthogonal to the length direction of the electrode fingers 3 and 4.

[0057] Here, the electrode finger 3 and the electrode finger 4 are adjacent to each other, which does not mean that the electrode finger 3 and the electrode finger 4 are arranged in direct contact, but means that the electrode finger 3 and the electrode finger 4 are arranged with a gap therebetween. In addition, when the electrode finger 3 and the electrode finger 4 are adjacent to each other, no electrode connected to the signal (hot) electrode and the ground electrode including other electrode fingers 3 and electrode fingers 4 is arranged between the electrode finger 3 and the electrode finger 4. The number of pairs does not need to be an integer pair, and may be 1.5 pairs or 2.5 pairs, etc.

[0058] The center-to-center distance, i.e., the spacing, between electrode fingers 3 and 4 is preferably in the range of 1 μm or more and 10 μm or less. In addition, the center-to-center distance between electrode fingers 3 and 4 is the distance obtained by connecting the center of the width dimension of electrode finger 3 in a direction perpendicular to the length direction of electrode finger 3 and the center of the width dimension of electrode finger 4 in a direction perpendicular to the length direction of electrode finger 4.

[0059] Furthermore, when at least one of the electrode fingers 3 and the electrode fingers 4 has multiple electrodes (when the electrode fingers 3 and the electrode fingers 4 are set as a pair of electrode groups and there are more than 1.5 pairs of electrode groups), the center-to-center distance of the electrode fingers 3 and the electrode fingers 4 refers to the average value of the center-to-center distances of adjacent electrode fingers 3 and the electrode fingers 4 in the more than 1.5 pairs of electrode fingers 3 and the electrode fingers 4.

[0060] In addition, the width of the electrode finger 3 and the electrode finger 4, that is, the dimension of the electrode finger 3 and the electrode finger 4 in the opposing direction, is preferably in the range of 150 nm or more and 1000 nm or less. In addition, the center-to-center distance between the electrode finger 3 and the electrode finger 4 is the distance obtained by connecting the center of the dimension (width dimension) of the electrode finger 3 in the direction orthogonal to the length direction of the electrode finger 3 and the center of the dimension (width dimension) of the electrode finger 4 in the direction orthogonal to the length direction of the electrode finger 4.

[0061] In the first embodiment, a Z-cut piezoelectric layer is used, so the direction orthogonal to the length direction of the electrode fingers 3 and 4 is the direction orthogonal to the polarization direction of the piezoelectric layer 2. This is not limited to the case where a piezoelectric body with another cutting angle is used as the piezoelectric layer 2. Here, "orthogonal" is not limited to the case of being strictly orthogonal, but may be approximately orthogonal (the angle formed by the direction orthogonal to the length direction of the electrode fingers 3 and 4 and the polarization direction is, for example, 90°±10°).

[0062] On the second main surface 2b side of the piezoelectric layer 2, a support substrate 8 is stacked via an intermediate layer 7. The intermediate layer 7 and the support substrate 8 form a support member. The intermediate layer 7 and the support substrate 8 have a frame-like shape, such as Figure 2 As shown, the support substrate 8 has openings 7a and 8a. Thus, a space portion (air gap) 9 is formed. In addition, the support substrate 8 may also have a shape having a recessed portion. In addition, the space portion 9 may also be formed by a recessed portion provided in the intermediate layer.

[0063] The space portion 9 is provided so as not to hinder the vibration of the excitation region C of the piezoelectric layer 2. Therefore, the support substrate 8 is laminated on the second main surface 2b via the intermediate layer 7 at a position that does not overlap with the portion where at least one pair of electrode fingers 3 and electrode fingers 4 are provided. In addition, the support substrate 8 can be laminated directly or indirectly on the second main surface 2b of the piezoelectric layer 2. That is, the intermediate layer 7 may not be provided. In this case, the support substrate 8 forms a support member.

[0064] The intermediate layer 7 is made of silicon oxide. However, the intermediate layer 7 may be made of a suitable insulating material other than silicon oxide, such as silicon nitride or alumina.

[0065] The supporting substrate 8 is formed of Si. The surface orientation of the Si on the piezoelectric layer 2 side can be (100), (110), or (111). Preferably, high-resistance Si with a resistivity of more than 4 kΩ is suitable. However, the supporting substrate 8 can also be composed of appropriate insulating materials or semiconductor materials. As the material of the supporting substrate 8, for example, piezoelectrics such as aluminum oxide, lithium tantalate, lithium niobate, and quartz, alumina, magnesium oxide, sapphire, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, forsterite, various ceramics, dielectrics such as diamond and glass, semiconductors such as gallium nitride, etc. can be used.

[0066] The plurality of electrode fingers 3, electrode fingers 4, first bus bar 5, and second bus bar 6 include appropriate metals or alloys such as Al and AlCu alloy. In the first embodiment, the electrode fingers 3, electrode fingers 4, first bus bar 5, and second bus bar 6 have a structure in which an Al film is stacked on a Ti film. Alternatively, a bonding layer other than a Ti film may be used.

[0067] During driving, an AC voltage is applied between the electrode fingers 3 and the electrode fingers 4. More specifically, an AC voltage is applied between the first bus bar 5 and the second bus bar 6. This can obtain resonance characteristics using bulk waves of the thickness shear first-order mode excited in the piezoelectric layer 2.

[0068] In the elastic wave device 1, when the thickness of the piezoelectric layer 2 is d and the center-to-center distance between any adjacent electrode fingers 3 and 4 in the plurality of pairs of electrode fingers 3 and 4 is p, d / p is set to be 0.5 or less. Therefore, the bulk wave of the thickness shear first-order mode can be effectively excited, and good resonance characteristics can be obtained. More preferably, d / p is 0.24 or less, in which case, even better resonance characteristics can be obtained.

[0069] In addition, when at least one of the electrode fingers 3 and the electrode fingers 4 has multiple electrodes as in the first embodiment, that is, when the electrode fingers 3 and the electrode fingers 4 are set as a pair of electrode groups and the electrode fingers 3 and the electrode fingers 4 have more than 1.5 pairs, the distance between the centers of adjacent electrode fingers 3 and the electrode fingers 4 becomes the average distance between the centers of each adjacent electrode finger 3 and the electrode finger 4.

[0070] In the elastic wave device 1 of the first embodiment, since it has the above-mentioned structure, even if the number of pairs of electrode fingers 3 and 4 is reduced for miniaturization, the Q value is unlikely to decrease. This is because the resonator does not require reflectors on both sides and the propagation loss is small. In addition, the reflectors are not required because the bulk wave of the thickness shear first-order mode is used.

[0071] Figure 3A It is a schematic cross-sectional view for explaining Lamb waves propagating through the piezoelectric layer of the comparative example. Figure 3B Schematic cross-sectional view for explaining a bulk wave of a thickness shear first-order mode propagating through the piezoelectric layer in the first embodiment. Figure 4 Schematic cross-sectional view for explaining the amplitude direction of a bulk wave of a thickness shear first-order mode propagating through the piezoelectric layer in the first embodiment.

[0072] exist Figure 3A In the elastic wave device described in Patent Document 1, Lamb waves propagate in the piezoelectric layer. Figure 3A As shown, the wave propagates in the piezoelectric layer 201 as shown by the arrow. Here, the piezoelectric layer 201 has a first main surface 201a and a second main surface 201b, and the thickness direction connecting the first main surface 201a and the second main surface 201b is the Z direction. The X direction is the direction in which the electrode fingers 3 and 4 of the IDT electrode are arranged. Figure 3AAs shown in the figure, for Lamb waves, the waves propagate in the X direction as shown in the figure. Since it is a plate wave, although the piezoelectric layer 201 vibrates as a whole, since the wave propagates in the X direction, reflectors are arranged on both sides to obtain resonance characteristics. Therefore, wave propagation loss occurs, and when miniaturization is achieved, that is, when the number of pairs of electrode fingers 3 and 4 is reduced, the Q value decreases.

[0073] In contrast, Figure 3B As shown, in the elastic wave device of the first embodiment, the vibration displacement is in the thickness shear direction, so the wave propagates and resonates roughly along the direction connecting the first main surface 2a and the second main surface 2b of the piezoelectric layer 2, that is, the Z direction. That is, the X-direction component of the wave is significantly smaller than the Z-direction component. Moreover, the resonance characteristic is obtained by the propagation of the wave in the Z direction, so a reflector is not required. Therefore, no propagation loss is generated when propagating to the reflector. Therefore, even if the number of pairs of electrode pairs including electrode fingers 3 and electrode fingers 4 is reduced in order to promote miniaturization, it is difficult to cause a decrease in the Q value.

[0074] In addition, if Figure 4 As shown, the amplitude direction of the body wave of the thickness shear first-order mode is in the excitation region C of the piezoelectric layer 2 (refer to Figure 1B ) and the second area 252 contained in the excitation area C are opposite. Figure 4 , a body wave is schematically shown when a voltage is applied between electrode finger 3 and electrode finger 4 so that electrode finger 4 has a higher potential than electrode finger 3. The first region 251 is a region between the first principal surface 2a and the imaginary plane VP1 that is orthogonal to the thickness direction of the piezoelectric layer 2 and divides the piezoelectric layer 2 into two parts in the excitation region C. The second region 252 is a region between the imaginary plane VP1 and the second principal surface 2b in the excitation region C.

[0075] In elastic wave device 1 , at least one pair of electrodes including electrode fingers 3 and electrode fingers 4 is provided. However, since the wave is not propagated in the X direction, the number of electrode pairs including electrode fingers 3 and electrode fingers 4 does not necessarily need to be plural. In other words, at least one pair of electrodes is sufficient.

[0076] For example, the electrode finger 3 is an electrode connected to the signal potential, and the electrode finger 4 is an electrode connected to the ground potential. However, the electrode finger 3 may be connected to the ground potential, and the electrode finger 4 may be connected to the signal potential. In the first embodiment, as described above, at least one pair of electrodes is an electrode connected to the signal potential or an electrode connected to the ground potential, and no floating electrode is provided.

[0077] Figure 5 is an explanatory diagram showing an example of the resonance characteristics of the elastic wave device according to the first embodiment. Figure 5The design parameters of elastic wave device 1 showing the resonance characteristics are as follows.

[0078] Piezoelectric layer 2: LiNbO3 with Euler angles (0°, 0°, 90°)

[0079] Thickness of piezoelectric layer 2: 400nm

[0080] Excitation area C (refer to Figure 1B ) length: 40μm

[0081] Number of pairs of electrodes including electrode finger 3 and electrode finger 4: 21 pairs

[0082] Center-to-center distance (pitch) between electrode finger 3 and electrode finger 4: 3 μm

[0083] Width of electrode finger 3 and electrode finger 4: 500nm

[0084] d / p:0.133

[0085] Intermediate layer 7: 1 μm thick silicon oxide film

[0086] Support substrate 8: Si

[0087] In addition, the excitation area C (refer to Figure 1B ) refers to the region where the electrode finger 3 overlaps the electrode finger 4 when viewed along the X direction orthogonal to the length direction of the electrode finger 3 and the electrode finger 4. The length of the excitation region C refers to the dimension of the excitation region C along the length direction of the electrode finger 3 and the electrode finger 4. Here, the excitation region C is an example of an “intersection region”.

[0088] In the first embodiment, the center-to-center distances of the electrode pairs including the electrode fingers 3 and the electrode fingers 4 are all equal in a plurality of pairs. That is, the electrode fingers 3 and the electrode fingers 4 are arranged at equal intervals.

[0089] according to Figure 5 It is clear that good resonance characteristics with a relative bandwidth of 12.5% ​​are obtained despite the absence of a reflector.

[0090] In addition, when the thickness of the piezoelectric layer 2 is d and the center-to-center distance between the electrode fingers 3 and 4 is p, in the first embodiment, d / p is 0.5 or less, and more preferably 0.24 or less. Figure 6 This is explained.

[0091] and get Figure 5 The elastic wave devices having the same resonance characteristics as shown above are obtained by changing d / 2p to obtain a plurality of elastic wave devices. Figure 6This is an explanatory diagram showing the relationship between d / 2p and the relative bandwidth of the resonator when the center-to-center distance or the average distance between the centers of adjacent electrodes is set to p and the average thickness of the piezoelectric layer 2 is set to d in the elastic wave device of the first embodiment.

[0092] like Figure 6 As shown, when d / 2p exceeds 0.25, that is, when d / p>0.5, even if d / p is adjusted, the relative bandwidth is less than 5%. In contrast, when d / 2p≤0.25, that is, d / p≤0.5, if d / p is changed within this range, the relative bandwidth can be made greater than 5%, that is, a resonator with a high coupling coefficient can be constructed. In addition, when d / 2p is less than 0.12, that is, when d / p is less than 0.24, the relative bandwidth can be increased to more than 7%. In addition, if d / p is adjusted within this range, a resonator with a wider relative bandwidth can be obtained, and a resonator with a higher coupling coefficient can be realized. Therefore, it can be seen that by setting d / p to less than 0.5, a resonator with a high coupling coefficient that utilizes the body wave of the above-mentioned thickness shear first-order mode can be constructed.

[0093] Furthermore, at least one pair of electrodes may be a pair, and in the case of a pair of electrodes, the above p is the distance between the centers of adjacent electrode fingers 3 and 4. In the case of more than 1.5 pairs of electrodes, the average distance between the centers of adjacent electrode fingers 3 and 4 may be set to p.

[0094] In addition, regarding the thickness d of the piezoelectric layer 2 , even when the piezoelectric layer 2 has thickness variations, a value obtained by averaging the thicknesses may be used.

[0095] Figure 7 1 is a schematic top view showing an example in which a pair of electrodes is provided in the elastic wave device of the first embodiment. In the elastic wave device 101, a pair of electrodes including electrode fingers 3 and electrode fingers 4 are provided on the first principal surface 2a of the piezoelectric layer 2. Figure 7 K in is the crossing width. As described above, in the elastic wave device of the present disclosure, the number of pairs of electrodes may be one pair. Even in this case, if the above d / p is 0.5 or less, the bulk wave of the thickness shear first-order mode can be effectively excited.

[0096] In the elastic wave device 1, it is preferred that the metallization ratio MR of any adjacent electrode fingers 3 and electrode fingers 4 among the plurality of electrode fingers 3 and electrode fingers 4 relative to the excitation region C satisfies MR≤1.75(d / p)+0.075, and the excitation region C is a region where the adjacent electrode fingers 3 and electrode fingers 4 overlap when viewed in opposite directions. In this case, the stray can be effectively reduced. Figure 8 and Fig. 9This is explained.

[0097] Figure 8 This is a reference diagram showing an example of the resonance characteristics of the elastic wave device of the first embodiment. Spurious signals indicated by arrow B appear between the resonance frequency and the antiresonance frequency. In addition, d / p=0.08 and the Euler angles of LiNbO3 are set to (0°, 0°, 90°). In addition, the metallization ratio MR is set to 0.35.

[0098] Reference Figure 1B The metallization ratio MR is described below. Figure 1B In the electrode structure, when focusing on a pair of electrode fingers 3 and electrode fingers 4, it is assumed that only the pair of electrode fingers 3 and electrode fingers 4 are provided. In this case, the portion surrounded by the single-dot chain line becomes the excitation region C. The excitation region C refers to the region where the electrode finger 3 overlaps with the electrode finger 4, the region where the electrode finger 4 overlaps with the electrode finger 3, and the region where the electrode finger 3 and the electrode finger 4 overlap with each other when the electrode finger 3 and the electrode finger 4 are observed along the direction orthogonal to the length direction of the electrode finger 3 and the electrode finger 4, that is, the opposing direction. And the area of ​​the electrode finger 3 and the electrode finger 4 in the excitation region C relative to the area of ​​the excitation region C is the metallization ratio MR. That is, the metallization ratio MR is the ratio of the area of ​​the metallized portion to the area of ​​the excitation region C.

[0099] When a plurality of pairs of electrode fingers 3 and electrode fingers 4 are provided, the ratio of the total area of ​​the metallized portions included in all the excitation regions C to the excitation regions C may be defined as MR.

[0100] Fig. 9 This is an explanatory diagram showing the relationship between the relative bandwidth and the phase rotation amount of the impedance of the stray normalized by 180 degrees, which is the magnitude of the stray, when the elastic wave device of the first embodiment is composed of a plurality of elastic wave resonators. In addition, the relative bandwidth is adjusted by making various changes to the film thickness of the piezoelectric layer 2 and the dimensions of the electrode fingers 3 and 4. In addition, Fig. 9 These are the results obtained when the piezoelectric layer 2 including Z-cut LiNbO 3 is used, but the same tendency is observed when the piezoelectric layer 2 having other cut angles is used.

[0101] exist Fig. 9 In the area enclosed by the ellipse J in the figure, the spurious signal increases to 1.0. Fig. 9 It is clear that when the relative bandwidth exceeds 0.17, that is, exceeds 17%, even if the parameters constituting the relative bandwidth are changed, large spurious signals with a spurious level of 1 or more appear in the passband. Figure 8As shown in the resonance characteristics, large spurious signals indicated by arrow B appear in the frequency band. Therefore, the relative bandwidth is preferably 17% or less. In this case, spurious signals can be reduced by adjusting the film thickness of the piezoelectric layer 2, the size of the electrode fingers 3 and 4, and the like.

[0102] Fig.10 1 is an explanatory diagram showing the relationship between d / 2p, metallization ratio MR, and relative bandwidth. In the elastic wave device 1 according to the first embodiment, various elastic wave devices 1 having different d / 2p and MR were constructed, and the relative bandwidth was measured. Fig.10 The hatched portion on the right side of the dotted line D is an area where the relative bandwidth is less than 17%. The boundary between the hatched area and the unhatched area is represented by MR=3.5(d / 2p)+0.075. That is, MR=1.75(d / p)+0.075. Therefore, it is preferred that MR≤1.75(d / p)+0.075. In this case, it is easy to make the relative bandwidth less than 17%. More preferred is Fig.10 The region to the right of MR=3.5(d / 2p)+0.05 indicated by the dashed line D1 in FIG. In other words, if MR≤1.75(d / p)+0.05, the relative bandwidth can be reliably made 17% or less.

[0103] Fig.11 This is an explanatory diagram showing a map of the relative bandwidth with respect to the Euler angle (0°, θ, ψ) of LiNbO 3 when d / p is made as close to 0 as possible. Fig.11 The hatched portion of is a region where a relative bandwidth of at least 5% is obtained. When the range of the region is approximated, it becomes a range represented by the following equations (1), (2), and (3).

[0104] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0105] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, {180°-60°(1-(θ-50) 2 / 900) 1 / 2}~180°) …Formula (2)

[0106] (0°±10°, {180°-30° (1-(ψ-90)) 2 / 8100) 1 / 2}~180°, arbitrary ψ) …Formula (3)

[0107] Therefore, in the case of the Euler angle range of the above-mentioned formula (1), formula (2) or formula (3), the relative bandwidth can be sufficiently widened, which is preferable.

[0108] Fig.12 FIG. 1 is a partially cutaway perspective view for explaining an elastic wave device according to an embodiment of the present disclosure. Fig.12 In FIG. 1 , the outer periphery of the space portion 9 is shown by a dotted line. The elastic wave device disclosed in the present invention may also utilize plate waves. In this case, Fig.12 As shown, the elastic wave device 301 has reflectors 310 and 311. The reflectors 310 and 311 are arranged on both sides of the elastic wave propagation direction of the electrode fingers 3 and 4 of the piezoelectric layer 2. In the elastic wave device 301, Lamb waves as plate waves are excited by applying an alternating electric field to the electrode fingers 3 and 4 on the space portion 9. At this time, since the reflectors 310 and 311 are arranged on both sides, the resonance characteristics based on the Lamb waves as plate waves can be obtained.

[0109] As described above, in the elastic wave devices 1 and 101, the bulk wave of the thickness shear first-order mode is used. In addition, in the elastic wave devices 1 and 101, the first electrode finger 3 and the second electrode finger 4 are adjacent electrodes, and when the thickness of the piezoelectric layer 2 is d and the center distance between the first electrode finger 3 and the second electrode finger 4 is p, d / p is set to be less than 0.5. Thus, even if the elastic wave device is miniaturized, the Q value can be improved.

[0110] In the elastic wave device 1, 101, the piezoelectric layer 2 is formed of lithium niobate or lithium tantalate. On the first principal surface 2a or the second principal surface 2b of the piezoelectric layer 2, there are first electrode fingers 3 and second electrode fingers 4 facing each other in a direction intersecting the thickness direction of the piezoelectric layer 2, and it is preferable to cover the first electrode fingers 3 and the second electrode fingers 4 with a protective film.

[0111] Fig.13 This is a schematic plan view showing an example of the elastic wave device according to the first embodiment. Fig.14 It is along Fig.13 A cross-sectional view of line XIV-XIV. Fig.15 It is along Fig.13 A cross-sectional view of line XV-XV. Fig.16 yes Fig.14 An enlarged cross-sectional view of region E. In addition, Fig.13 In the figure, the protective film 19 is omitted, and the range of the insulating film 19a of the first component described later is recorded with a double-dashed line. Figures 13 to 15 As shown, an elastic wave device 1A according to the first embodiment includes a supporting member 80 , a piezoelectric layer 2 , a functional electrode 30 , a wiring electrode 14 , and a protective film 19 .

[0112] The support member 80 has a support substrate 8. In the first embodiment, the support member 80 includes an intermediate layer 7 and a support substrate 8. The intermediate layer 7 is provided on the piezoelectric layer 2 side of the support substrate 8 in the Z direction.

[0113] The support member 80 has a space 9. The space 9 is a space that is open on the piezoelectric layer 2 side of the support member 80. In the first embodiment, the space 9 is located in the intermediate layer 7. Fig.14 and Fig.15 In the example, the space portion 9 is located on the piezoelectric layer side of the intermediate layer 7 in the Z direction. That is, the space portion 9 can be said to be a space located between the piezoelectric layer 2 and the supporting substrate 8. In addition, the space portion 9 may also be a space that penetrates the intermediate layer 7 in the Z direction.

[0114] like Fig.13 As shown in the first embodiment, the edge of the space portion 9 is a rectangular shape with both sides in the X direction protruding outward in the X direction. The edge of the space portion 9 refers to the boundary between the area overlapping with the space portion 9 and the area not overlapping with the space portion 9 when viewed from above in the Z direction. Fig.13 In the example, the edges of the space portion 9 on both sides of the Y direction are two straight lines extending in the X direction, and the edges of the space portion 9 on both sides of the X direction are shaped to protrude outward in the X direction. In the following description, the portion of the space portion 9 protruding outward in the X direction is described as a lead portion.

[0115] The piezoelectric layer 2 is disposed on the side of the space portion 9 in the Z direction of the support member 80. In the first embodiment, the piezoelectric layer 2 is disposed on the side of the intermediate layer 7 of the support member 80. In the following description, the surface of the piezoelectric layer 2 on the side of the support member 80 is sometimes set as the second principal surface 2b, and the surface on the side opposite to the second principal surface 2b in the Z direction is sometimes set as the first principal surface 2a for description.

[0116] The piezoelectric layer 2 has a through hole 2H. The through hole 2H is a hole that penetrates the piezoelectric layer 2 in the Z direction. The through hole 2H is provided at a position that does not overlap with the functional electrode 30 when viewed from above in the Z direction. In the first embodiment, the through hole 2H is provided at a position that does not overlap with the functional electrode 30 and the wiring electrode 14 when viewed from above in the Z direction, and is at a position that overlaps with the space portion 9. That is, the through hole 2H is connected to the space portion 9. Fig.13 In the example, the through hole 2H is provided at a position overlapping with the lead portion of the space portion 9 when viewed from above along the Z direction. In addition, the position of the through hole 2H is not limited thereto, and the through hole 2H may be provided along the Y direction of the electrode fingers 3 and 4 and surrounded by the wiring electrode 14.

[0117] The functional electrode 30 is an IDT electrode having electrode fingers 3, 4 and bus bars 5, 6. Fig.13In the example, the functional electrode 30 is arranged on the first principal surface 2a of the piezoelectric layer 2. The functional electrode 30 is an example of a pair of electrodes. A pair of electrodes refers to a group of electrodes including a first electrode and a second electrode that are opposite to each other in a direction intersecting the Z direction and are adjacently arranged on the principal surface of the piezoelectric layer 2. Here, the first electrode and the second electrode are adjacent to each other means that no other electrode is arranged between the first electrode and the second electrode on the same principal surface of the piezoelectric layer 2. In the first embodiment, the electrode finger 3 and the first bus bar 5 are equivalent to the first electrode, and the electrode finger 4 and the second bus bar 6 are equivalent to the second electrode. In addition, the number of functional electrodes 30 is not particularly limited, and at least one may be provided.

[0118] In the first embodiment, the bus bars 5 and 6 are arranged so as to overlap with the corner 9a of the space portion 9 when viewed from above in the Z direction. The corner 9a of the space portion 9 refers to the point on the edge of the space portion 9 closest to the intersection of the edge of the space portion 9 located on both sides of the X direction and the edge of the space portion 9 located on both sides of the Y direction, or the point on the edge of the space portion 9 closest to the intersection of the extension line of the edge of the space portion 9 located on both sides of the X direction and the extension line of the edge of the space portion 9 located on both sides of the Y direction. That is, the corner 9a is a point equivalent to the vertex of the edge of the space portion 9. Thereby, the concentration of stress on the piezoelectric layer 2 can be alleviated, and the generation of cracks in the piezoelectric layer 2 can be suppressed.

[0119] The wiring electrode 14 is provided on the first main surface 2 a side with respect to the piezoelectric layer 2 . In the first embodiment, the wiring electrode 14 is a metal layer, for example, an alloy including Al and Cu. The wiring electrode 14 is laminated on a part of the bus bars 5 , 6 of the functional electrode 30 .

[0120] The protective film 19 is a film provided on the functional electrode 30. Fig.14 In the example of FIG. 1 , the protective film 19 is provided over the entire first main surface 2a of the piezoelectric layer 2 so as to cover the functional electrode 30 and the wiring electrode 14. Fig.16 As shown, the protective film 19 includes an insulating film 19 a of a first component in contact with the functional electrode 30 and an insulating film 19 b of a second component as a surface layer.

[0121] The insulating film 19a of the first component is in contact with the functional electrode 30. Being in contact with the functional electrode 30 includes being in contact with a portion of the functional electrode 30. In the first embodiment, the insulating film 19a of the first component is provided at a position overlapping with the space portion 9 in a plan view along the Z direction. Fig.14 and Fig.15 In the example of FIG. 1 , the insulating film 19 a of the first component is provided to cover the functional electrode 30 and the wiring electrode 14 on the side opposite to the piezoelectric layer 2 .

[0122] The insulating film 19b of the second component is located on the surface layer of the protective film 19. That is, the insulating film 19b of the second component is provided to cover the insulating film 19a of the first component. In the first embodiment, the insulating film 19b of the second component is provided over the entire surface of the first principal surface 2a of the piezoelectric layer 2 so as to cover the insulating film 19a of the first component. In other words, the protective film 19 has a portion including the insulating film 19a of the first component and the insulating film 19b of the second component and a portion which is a single layer of the insulating film 19b of the second component when viewed from above along the Z direction. Fig.14 In the example, in the portion of the second component insulating film 19b being a single layer, the second component insulating film 19b is in contact with the first principal surface 2a of the piezoelectric layer 2. Thus, the first component insulating film 19a is protected by the second component insulating film 19b as a surface layer.

[0123] The first component insulating film 19a has higher moisture resistance than the second component insulating film 19b. That is, the first component insulating film 19a is less likely to absorb moisture in the air than the second component insulating film 19b. Thus, the first component insulating film 19a in contact with the electrode fingers 3 and 4 can be prevented from absorbing moisture in the air, thereby preventing the frequency characteristics from changing.

[0124] The level of moisture resistance can be determined by the following method. First, the insulating film 19a of the first component and the insulating film 19b of the second component are placed in an atmosphere of a temperature of 85°C and a humidity of 85% for 100 hours to allow them to absorb moisture. Then, the amount of moisture released by performing a temperature-increased degassing analysis on the insulating film 19a of the first component and the insulating film 19b of the second component is measured. At this time, if the insulating film 19b of the second component releases more moisture than the insulating film 19a of the first component, it can be said that the insulating film 19a of the first component has higher moisture resistance than the insulating film 19b of the second component.

[0125] The insulating film 19b of the second component has a higher plasma resistance than the insulating film 19a of the first component. That is, the insulating film 19b of the second component is less likely to be oxidized when exposed to plasma than the insulating film 19a of the first component. Thus, it is possible to suppress oxidation of the insulating film 19b of the second component on the surface when exposed to plasma during the manufacturing process of the elastic wave device, thereby suppressing fluctuations in frequency characteristics.

[0126] The level of plasma resistance can be determined by the following method. First, the insulating film 19a of the first component and the insulating film 19b of the second component are exposed to plasma. The plasma exposure is performed, for example, under the same conditions as the plasma ashing performed by removing the resists R1 and R2 in the through-hole forming process or etching process described later. Then, the composition ratio of oxygen contained in the insulating film 19a of the first component and the insulating film 19b of the second component is measured by TEM-EDX method, XPS method or RBS (Rutherford backscattering analysis method). At this time, if the increase in the composition ratio of oxygen before exposure to plasma is smaller in the insulating film 19b of the second component than in the insulating film 19a of the first component, it can be said that the insulating film 19b of the second component has higher plasma resistance than the insulating film 19a of the first component.

[0127] In the first embodiment, the insulating film 19b of the second component is thinner than the insulating film 19a of the first component. For example, the thickness of the insulating film 19a of the first component can be set to 15 nm, and the thickness of the insulating film 19b of the second component can be set to 5 nm. Thus, the insulating film 19a of the first component can be protected from plasma damage during the manufacturing process of the elastic wave device 1A while suppressing the change of the frequency characteristics caused by the moisture absorption of the insulating film 19b of the second component. In addition, when the elastic wave device 1A has a plurality of functional electrodes 30, the insulating film 19a of the first component can also be made to have a different thickness for each functional electrode 30 connected.

[0128] In the first embodiment, the insulating film 19a of the first component is a silicon nitride (SiN) film, and the insulating film 19b of the second component is a silicon nitride oxide (SiON) film. As a result, the insulating film 19a of the first component can have higher moisture resistance than the insulating film 19b of the second component, and the insulating film 19b of the second component can have higher plasma resistance than the insulating film 19a of the first component, so that the frequency characteristic fluctuation can be suppressed.

[0129] As mentioned above, the elastic wave device 1A according to the first embodiment has been described, but the elastic wave device according to the first embodiment is not limited to the elastic wave device described above.

[0130] For example, the combination of materials of the first component insulating film 19a and the second component insulating film 19b is not limited to the combination described above. In the following description, the oxygen content of the insulating film refers to the composition ratio of oxygen contained in the insulating film.

[0131] In the elastic wave device according to the first modification, the insulating film 19a of the first component is a silicon nitride (SiN) film, and the insulating film 19b of the second component is a silicon oxide (SiO2) film. In this case, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0132] In the elastic wave device according to the second modification, the insulating film 19a of the first component and the insulating film 19b of the second component are silicon oxynitride (SiON) films. Here, the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. In this case, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0133] In the elastic wave device according to the third modification, the insulating film 19a of the first component is a silicon nitride oxide (SiON) film, and the insulating film 19b of the second component is a silicon oxide (SiO2) film. In this case, the insulating film 19a of the first component can have higher moisture resistance than the insulating film 19b of the second component, and the insulating film 19b of the second component can have higher plasma resistance than the insulating film 19a of the first component, so that the frequency characteristic fluctuation can be suppressed.

[0134] In the elastic wave device according to the fourth modification, the insulating film 19a of the first component and the insulating film 19b of the second component are aluminum oxide films (Al2O3 films). Here, the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. In this case, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0135] In the elastic wave device according to the fifth modification, the insulating film 19a of the first component and the insulating film 19b of the second component are titanium oxide films (TiO2 films). Here, the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. In this case, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0136] In the elastic wave device according to the sixth modification, the insulating film 19a of the first component and the insulating film 19b of the second component are tantalum oxide films (Ta2O5 films). Here, the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. In this case, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0137] As described above, the elastic wave device 1A according to the first embodiment includes: the piezoelectric layer 2 having the first main surface 2a and the second main surface 2b facing each other in the first direction; at least one pair of electrodes (electrode fingers 3, 4) provided on at least one of the first main surface 2a and the second main surface 2b; and the protective film 19 covering at least a portion of the pair of electrodes. The protective film 19 includes an insulating film 19a of a first component in contact with the pair of electrodes and an insulating film 19b of a second component as a surface layer. The insulating film 19a of the first component has higher moisture resistance than the insulating film 19b of the second component. The insulating film 19b of the second component has higher plasma resistance than the insulating film 19a of the first component. Thus, the insulating film 19a of the first component in contact with the electrode fingers 3, 4 can be prevented from absorbing moisture in the air, and the insulating film 19b of the second component as a surface layer can be prevented from being oxidized when exposed to plasma during the manufacturing process of the elastic wave device, thereby preventing the frequency characteristics from changing.

[0138] As a desirable mode, the insulating film 19a of the first component is a silicon nitride film, and the insulating film 19b of the second component is a silicon nitride oxide film. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0139] As a desirable mode, the insulating film 19a of the first component is a silicon nitride film, and the insulating film 19b of the second component is a silicon oxide film. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0140] As a desirable mode, the insulating film 19a of the first component and the insulating film 19b of the second component are silicon nitride oxide films, and the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, so that the frequency characteristic fluctuation can be suppressed.

[0141] As a desirable mode, the insulating film 19a of the first component is a silicon nitride oxide film, and the insulating film 19b of the second component is a silicon oxide film. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, thereby suppressing the change in frequency characteristics.

[0142] As a desirable mode, the insulating film 19a of the first component and the insulating film 19b of the second component are aluminum oxide films, and the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, so that the frequency characteristic fluctuation can be suppressed.

[0143] As a desirable mode, the insulating film 19a of the first component and the insulating film 19b of the second component are titanium oxide films, and the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, so that the frequency characteristic fluctuation can be suppressed.

[0144] As a desirable mode, the insulating film 19a of the first component and the insulating film 19b of the second component are tantalum oxide films, and the insulating film 19b of the second component has a higher oxygen content than the insulating film 19a of the first component. Thus, the insulating film 19a of the first component can be made more resistant to moisture than the insulating film 19b of the second component, and the insulating film 19b of the second component can be made more resistant to plasma than the insulating film 19a of the first component, so that the frequency characteristic fluctuation can be suppressed.

[0145] As a desired mode, a pair of electrodes is an IDT electrode, which includes a first bus bar 5 and a second bus bar 6 facing each other in a second direction intersecting the first direction, at least one first electrode finger 3 whose base end is connected to the first bus bar 5 and extends in the second direction, and at least one second electrode finger 4 whose base end is connected to the second bus bar 6 and extends in the second direction. Thus, good resonance characteristics are obtained.

[0146] As a desired mode, a support member 80 having a support substrate 8 is further provided. The piezoelectric layer 2 is provided in a first direction of the support member 80, which is a thickness direction of the support substrate 8. A space portion 9 opened on the piezoelectric layer 2 side in the first direction is provided in the support member 80. In a plan view from the first direction, at least a portion of the pair of electrodes overlaps with the space portion 9. Thus, a good resonance characteristic is obtained.

[0147] As a more preferred embodiment, the protective film 19 in the region overlapping the space portion 9 in the first direction includes a first component insulating film 19a in contact with a pair of electrodes and a second component insulating film 19b on the surface. Thus, the frequency characteristics can be improved by adjusting the film thickness of the first component insulating film 19a.

[0148] As a further desirable embodiment, the protective film 19 includes a portion including the insulating film 19a of the first component and the insulating film 19b of the second component, and a portion including only the insulating film 19b of the second component. The portion including the insulating film 19a of the first component and the insulating film 19b of the second component overlaps with the space portion 9 in the first direction. In the portion including only the insulating film 19b of the second component, the insulating film 19b of the second component is in direct contact with the piezoelectric layer 2. Thus, the insulating film 19a of the first component is protected by the insulating film 19b of the second component on the surface, and therefore, the insulating film 19a of the first component can be protected from destruction by plasma during the manufacture of the elastic wave device 1A, and thus, the frequency characteristic fluctuation can be further suppressed.

[0149] As a further desirable embodiment, the protective film 19 in the region not overlapping with the space portion 9 in the first direction includes only the insulating film 19b of the second component, and the insulating film 19b of the second component in the non-overlapping region is in direct contact with the piezoelectric layer 2. Thus, the insulating film 19a of the first component is protected by the insulating film 19b of the second component on the surface, and therefore, the insulating film 19a of the first component can be protected from destruction by plasma during the manufacture of the elastic wave device 1A, and thus, the frequency characteristic fluctuation can be further suppressed.

[0150] As a desired mode, a pair of electrodes is an IDT electrode, which includes a first bus bar 5 and a second bus bar 6 facing each other in a second direction intersecting the first direction, at least one first electrode finger 3 whose base end is connected to the first bus bar 5 and extends in the second direction, and at least one second electrode finger 4 whose base end is connected to the second bus bar 6 and extends in the second direction. The first bus bar 5 or the second bus bar 6 is arranged to overlap with the corner 9a of the space portion 9 when viewed from above in the first direction. Thereby, the concentration of stress on the piezoelectric layer 2 can be alleviated, and the generation of cracks in the piezoelectric layer 2 can be suppressed.

[0151] As a preferred embodiment, the Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer 2 are within the range of the following formula (1), formula (2), or formula (3). In this case, the relative bandwidth can be reliably set to 17% or less.

[0152] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0153] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2)

[0154] (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, any ψ) …Formula (3)

[0155] As a desired mode, a pair of electrodes is an IDT electrode, which includes a first bus bar 5 and a second bus bar 6 facing each other in a second direction intersecting the first direction, at least one first electrode finger 3 whose base end is connected to the first bus bar 5 and extends in the second direction, and at least one second electrode finger 4 whose base end is connected to the second bus bar 6 and extends in the second direction. When the film thickness of the piezoelectric layer 2 is set to d and the center-to-center distance between adjacent first electrode fingers 3 and second electrode fingers 4 is set to p, d / p is less than 0.5. As a result, the bulk wave of the thickness shear first-order mode can be effectively excited.

[0156] As a more desirable aspect, d / p is 0.24 or less. This makes it possible to more effectively excite the bulk wave of the thickness shear first-order mode.

[0157] As a desired method, a pair of electrodes is an IDT electrode, which includes a first bus bar 5 and a second bus bar 6 facing each other in a second direction intersecting the first direction, at least one first electrode finger 3 whose base end is connected to the first bus bar 5 and extends in the second direction, and at least one second electrode finger 4 whose base end is connected to the second bus bar 6 and extends in the second direction. The area where the adjacent first electrode fingers 3 and second electrode fingers 4 overlap when viewed in the opposite direction is an excitation area, and when the metallization rate of the plurality of first electrode fingers 3 and second electrode fingers 4 relative to the excitation area is set to MR, MR≤1.75(d / p)+0.075 is satisfied. Thus, the stray can be effectively reduced.

[0158] As a desirable aspect, a configuration is adopted in which a thickness shear mode bulk wave can be utilized. Thus, an elastic wave device having a high coupling coefficient and good resonance characteristics can be provided.

[0159] As a desirable aspect, a configuration is adopted in which plate waves can be utilized. Thus, an elastic wave device having good resonance characteristics can be provided.

[0160] The following describes a method for manufacturing an elastic wave device according to the first embodiment. The method for manufacturing an elastic wave device 1A according to the first embodiment includes a sacrificial layer forming step, an intermediate layer forming step, a bonding step, a thinning step, an electrode forming step, a first component insulating film forming step, a second component insulating film forming step, a through hole forming step, and an etching step.

[0161] Fig.17 Schematic cross-sectional view for explaining the sacrificial layer forming step of the method for manufacturing the elastic wave device according to the first embodiment. Fig.17 As shown, the sacrificial layer forming step is a step of forming the sacrificial layer 7S on the second main surface 2b of the piezoelectric layer 2. For example, after the sacrificial layer 7S is formed on the entire surface of the second main surface 2b of the piezoelectric layer 2, a portion of the sacrificial layer 7S of the piezoelectric layer 2 is removed by patterning the resist, thereby forming the sacrificial layer 7S. The resist is removed after the formation of the sacrificial layer 7S.

[0162] Fig.18 Schematic cross-sectional view for explaining the intermediate layer forming step of the method for manufacturing the elastic wave device according to the first embodiment. Fig.18 As shown, the intermediate layer forming process is a process of forming the intermediate layer 7 on the second main surface 2b of the piezoelectric layer 2 so as to cover the sacrificial layer 7S. For example, the intermediate layer 7 is formed on the second main surface 2b of the piezoelectric layer 2, and the main surface of the intermediate layer 7 on the side opposite to the piezoelectric layer 2 in the Z direction is ground, thereby forming the intermediate layer 7.

[0163] Fig.19Schematic cross-sectional view for explaining the bonding step of the method for manufacturing the elastic wave device according to the first embodiment. Fig.19 As shown, the bonding step is a step of bonding the support substrate 8 to the side of the intermediate layer 7 opposite to the piezoelectric layer 2 in the Z direction. In this way, a support member 80 including the intermediate layer 7 and the support substrate 8 is formed.

[0164] Fig. 20 Schematic cross-sectional view for explaining the thinning step of the method for manufacturing the elastic wave device according to the first embodiment. Fig. 20 As shown, the thinning step is a step of grinding the piezoelectric layer 2 to thin the piezoelectric layer 2. Thus, the first main surface 2a of the piezoelectric layer 2 is formed.

[0165] Fig.21 Schematic cross-sectional view for explaining the electrode forming step of the method for manufacturing the elastic wave device according to the first embodiment. Fig.21 As shown, the electrode forming step is a step of forming the functional electrode 30 on the first main surface 2a of the piezoelectric layer 2. The functional electrode 30 is formed by, for example, a lift-off method. After the functional electrode 30 is formed, the wiring electrode 14 is provided on the functional electrode 30.

[0166] Fig. 22 Schematic cross-sectional view for explaining the step of forming the insulating film of the first component of the method for manufacturing the elastic wave device according to the first embodiment. Fig. 22 As shown, the first component insulating film forming step is a step of forming the first component insulating film 19a on the first main surface 2a of the piezoelectric layer 2 so as to cover the functional electrode 30. Fig. 22 In the example, the insulating film 19a of the first component is provided at a position overlapping with the space portion 9 when viewed from above along the Z direction. After the insulating film 19a of the first component is formed, the film thickness of the insulating film 19a of the first component is adjusted so that the frequency characteristics of the elastic wave device 1A become the desired frequency characteristics. Here, the insulating film 19a of the first component has higher moisture resistance than the insulating film 19b of the second component described later, so that moisture absorption of the protective film 19 can be suppressed in the subsequent process, and the frequency characteristics can be suppressed from changing.

[0167] Fig.23 Schematic cross-sectional view for explaining the step of forming the insulating film of the second component in the method for manufacturing the elastic wave device according to the first embodiment. Fig.23 As shown, the second component insulating film forming step is a step of forming the second component insulating film 19b on the first main surface 2a of the piezoelectric layer 2 so as to cover the first component insulating film 19a. Fig.23In the example of FIG. 1 , the insulating film 19 b of the second component is provided over the entire surface of the first principal surface 2 a of the piezoelectric layer 2. Thus, the insulating film 19 a of the first component is protected by the insulating film 19 b of the second component.

[0168] Fig.24 Schematic cross-sectional view for explaining the through-hole forming step of the method for manufacturing the elastic wave device according to the first embodiment. Fig.24 As shown, the through hole forming process is a process of providing a through hole 2H in the piezoelectric layer 2. The through hole 2H is formed by forming a resist R1 on the first main surface 2a of the piezoelectric layer 2 and removing a portion of the piezoelectric layer 2. The resist R1 is removed by plasma ashing after the formation of the through hole 2H. At this time, an insulating film 19b of a second component having higher plasma resistance than the insulating film 19a of the first component is provided, so that oxidation of the protective film 19 during plasma ashing can be suppressed, and changes in frequency characteristics can be suppressed.

[0169] Fig.25 Schematic cross-sectional view for explaining the etching step of the method for manufacturing the elastic wave device according to the first embodiment. Fig.25 As shown, the etching process is a process of etching the sacrificial layer 7S to form the space portion 9. The sacrificial layer 7S is removed by forming a resist R2 on the first main surface 2a of the piezoelectric layer 2 and injecting an etching solution from the through hole 2H to remove the sacrificial layer 7S. The resist R2 is removed by plasma ashing after the etching of the sacrificial layer 7S. At this time, an insulating film 19b of a second component having higher plasma resistance than the insulating film 19a of the first component is provided, so that oxidation of the protective film 19 during plasma ashing can be suppressed, and changes in frequency characteristics can be suppressed.

[0170] The elastic wave device 1A according to the first embodiment can be manufactured through the above steps. The method for manufacturing the elastic wave device 1A according to the first embodiment described above is an example and is not limited thereto.

[0171] For example, instead of adjusting the thickness of the insulating film 19a of the first component after the insulating film 19a of the first component is formed, the thickness of the insulating film 19b of the second component may be adjusted after the insulating film 19b of the second component is formed, so that the frequency characteristics of the elastic wave device 1A become the desired frequency characteristics.

[0172] (Second embodiment)

[0173] Fig.261 is a schematic cross-sectional view showing an example of an elastic wave device according to the second embodiment. The elastic wave device 1B according to the second embodiment is different from the first embodiment in that it is a device using bulk waves, that is, a BAW (Bulk Acoustic Wave) element. Fig.26 As shown, in the second embodiment, the functional electrode 30A includes a first electrode 31 and a second electrode 32. The first electrode 31 is an electrode provided on the first main surface 2a, also referred to as an upper electrode. The second electrode 32 is an electrode provided on the second main surface 2b, also referred to as a lower electrode. Fig.26 In the example, the protective film 19 is provided over the entire surface of the first principal surface 2a and the second principal surface 2b of the piezoelectric layer 2 so as to cover the functional electrode 30 and the wiring electrode not shown. In addition, the protective film 19 may be provided on either the first principal surface 2a or the second principal surface 2b. In addition, the structure of the protective film 19 may be different on the first principal surface 2a and the second principal surface 2b. For example, an insulating film 19a of the first component and an insulating film 19b of the second component may be provided on the first principal surface 2a, while only an insulating film 19b of the second component may be provided on the second principal surface 2b.

[0174] As described above, in the elastic wave device 1B according to the second embodiment, a pair of electrodes (functional electrodes 30A) includes the first electrode 31 provided on the first principal surface 2a of the piezoelectric layer 2 and the second electrode 32 provided on the second principal surface 2b. In this case, the frequency characteristic can also be suppressed from changing.

[0175] In addition, the above-mentioned embodiments are for facilitating the understanding of the present disclosure, and are not for limiting the present disclosure. The present disclosure can be changed / improved within the scope of the present disclosure, and the present disclosure also includes its equivalents.

[0176] In addition, the present invention can also take the following aspects.

[0177] <1>

[0178] An elastic wave device comprising:

[0179] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0180] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0181] a protective film covering at least a portion of the pair of electrodes,

[0182] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0183] The insulating film of the first component has higher moisture resistance than the insulating film of the second component.

[0184] The insulating film of the second component has higher plasma resistance than the insulating film of the first component.

[0185] <2>

[0186] According to the elastic wave device described in <1>,

[0187] The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon nitride oxide film.

[0188] <3>

[0189] According to the elastic wave device described in <1>,

[0190] The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon oxide film.

[0191] <4>

[0192] According to the elastic wave device described in <1>,

[0193] The insulating film of the first component and the insulating film of the second component are silicon nitride oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0194] <5>

[0195] According to the elastic wave device described in <1>,

[0196] The insulating film of the first component is a silicon nitride oxide film, and the insulating film of the second component is a silicon oxide film.

[0197] <6>

[0198] According to the elastic wave device described in <1>,

[0199] The insulating film of the first component and the insulating film of the second component are aluminum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0200] <7>

[0201] According to the elastic wave device described in <1>,

[0202] The insulating film of the first component and the insulating film of the second component are titanium oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0203] <8>

[0204] According to the elastic wave device described in <1>,

[0205] The insulating film of the first component and the insulating film of the second component are tantalum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0206] <9>

[0207] An elastic wave device comprising:

[0208] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0209] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0210] a protective film covering at least a portion of the pair of electrodes,

[0211] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0212] The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon nitride oxide film.

[0213] <10>

[0214] An elastic wave device comprising:

[0215] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0216] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0217] a protective film covering at least a portion of the pair of electrodes,

[0218] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0219] The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon oxide film.

[0220] <11>

[0221] An elastic wave device comprising:

[0222] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0223] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0224] a protective film covering at least a portion of the pair of electrodes,

[0225] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0226] The insulating film of the first component and the insulating film of the second component are silicon nitride oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0227] <12>

[0228] An elastic wave device comprising:

[0229] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0230] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0231] a protective film covering at least a portion of the pair of electrodes,

[0232] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0233] The insulating film of the first component is a silicon nitride oxide film, and the insulating film of the second component is a silicon oxide film.

[0234] <13>

[0235] An elastic wave device comprising:

[0236] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0237] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0238] a protective film covering at least a portion of the pair of electrodes,

[0239] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0240] The insulating film of the first component and the insulating film of the second component are aluminum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0241] <14>

[0242] An elastic wave device comprising:

[0243] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0244] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0245] a protective film covering at least a portion of the pair of electrodes,

[0246] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0247] The insulating film of the first component and the insulating film of the second component are titanium oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0248] <15>

[0249] An elastic wave device comprising:

[0250] The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction;

[0251] at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and

[0252] a protective film covering at least a portion of the pair of electrodes,

[0253] The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface.

[0254] The insulating film of the first component and the insulating film of the second component are tantalum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

[0255] <16>

[0256] The elastic wave device according to any one of <1> to <15>,

[0257] The pair of electrodes is an IDT electrode, which includes a first bus bar and a second bus bar opposite to each other in a second direction intersecting the first direction, at least one first electrode finger whose base end is connected to the first bus bar and extends along the second direction, and at least one second electrode finger whose base end is connected to the second bus bar and extends along the second direction.

[0258] <17>

[0259] The elastic wave device according to any one of <1> to <16>,

[0260] The elastic wave device further includes a support member having a support substrate.

[0261] The piezoelectric layer is provided in the first direction of the support member, which is the thickness direction of the support substrate.

[0262] The support member is provided with a space portion opened on the piezoelectric layer side in the first direction,

[0263] At least a portion of the pair of electrodes overlaps with the space portion in a plan view as viewed from the first direction.

[0264] <18>

[0265] According to the elastic wave device described in <17>,

[0266] The protective film in a region overlapping the space portion in the first direction includes an insulating film of the first component in contact with the pair of electrodes and an insulating film of the second component as a surface layer.

[0267] <19>

[0268] According to the elastic wave device described in <18>,

[0269] The protective film has:

[0270] a portion including an insulating film of the first component and an insulating film of the second component; and

[0271] a portion of the insulating film including only the second component,

[0272] A portion including the insulating film of the first component and the insulating film of the second component overlaps the space portion in the first direction,

[0273] In a portion including only the insulating film of the second component, the insulating film of the second component is in direct contact with the piezoelectric layer.

[0274] <20>

[0275] According to the elastic wave device described in <18>,

[0276] The protective film in a region not overlapping with the space portion in the first direction includes only the insulating film of the second component, and the insulating film of the second component in the non-overlapping region is in direct contact with the piezoelectric layer.

[0277] <21>

[0278] According to the elastic wave device described in <16>,

[0279] The pair of electrodes is an IDT electrode, the IDT electrode including a first bus bar and a second bus bar facing each other in a second direction intersecting the first direction, at least one first electrode finger having a base end connected to the first bus bar and extending in the second direction, and at least one second electrode finger having a base end connected to the second bus bar and extending in the second direction,

[0280] The first bus bar or the second bus bar is provided so as to overlap with a corner of the space portion in a plan view along the first direction.

[0281] <22>

[0282] The elastic wave device according to any one of <1> to <21>,

[0283] The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3),

[0284] (0°±10°, 0°~20°, arbitrary ψ) …Formula (1)

[0285] (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2)

[0286] (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, arbitrary ψ) …Formula (3).

[0287] <23>

[0288] The elastic wave device according to any one of <1> to <22>,

[0289] The pair of electrodes is an IDT electrode, the IDT electrode including a first bus bar and a second bus bar facing each other in a second direction intersecting the first direction, at least one first electrode finger having a base end connected to the first bus bar and extending in the second direction, and at least one second electrode finger having a base end connected to the second bus bar and extending in the second direction,

[0290] When the film thickness of the piezoelectric layer is denoted by d and the center-to-center distance between the adjacent first electrode fingers and the second electrode fingers is denoted by p, d / p is equal to or less than 0.5.

[0291] <24>

[0292] According to the elastic wave device described in <23>,

[0293] The d / p is 0.24 or less.

[0294] <25>

[0295] The elastic wave device according to any one of <1> to <24>,

[0296] The pair of electrodes is an IDT electrode, the IDT electrode including a first bus bar and a second bus bar facing each other in a second direction intersecting the first direction, at least one first electrode finger having a base end connected to the first bus bar and extending in the second direction, and at least one second electrode finger having a base end connected to the second bus bar and extending in the second direction,

[0297] An area where adjacent first and second electrode fingers overlap when viewed in opposing directions is an excitation area, and when a metallization ratio of the first and second electrode fingers to the excitation area is MR, MR≤1.75(d / p)+0.075 is satisfied.

[0298] <26>

[0299] The elastic wave device according to any one of <1> to <25>,

[0300] The elastic wave device is configured to utilize thickness shear mode bulk waves.

[0301] <27>

[0302] The elastic wave device according to any one of <1> to <20>,

[0303] The elastic wave device is configured to utilize plate waves.

[0304] <28>

[0305] The elastic wave device according to any one of <1> to <15>,

[0306] The pair of electrodes includes a first electrode provided on the first principal surface of the piezoelectric layer, and a second electrode provided on the second principal surface.

[0307] Description of Reference Numerals

[0308] 1, 1A, 1B, 101, 301 elastic wave device;

[0309] 2 Piezoelectric layer;

[0310] 2a first main surface;

[0311] 2b second main surface;

[0312] 2H through hole;

[0313] 3 electrode fingers (first electrode fingers);

[0314] 4 electrode fingers (second electrode fingers);

[0315] 5 First bus bar;

[0316] 6 Second bus bar;

[0317] 7 Middle layer;

[0318] 7a opening;

[0319] 8 support base plate;

[0320] 8a opening;

[0321] 80 Supporting member;

[0322] 9. Ministry of Space;

[0323] 9a corner;

[0324] 14 wiring electrodes;

[0325] 19 protective film;

[0326] 19a an insulating film of a first component;

[0327] 19b an insulating film of a second component;

[0328] 30, 30A functional electrode;

[0329] 31 first electrode;

[0330] 32 second electrode;

[0331] 201 piezoelectric layer;

[0332] 201a first main surface;

[0333] 201b second main surface;

[0334] 251 First Region;

[0335] 252 Second Region;

[0336] 310, 311 reflectors;

[0337] C excitation region (crossover region);

[0338] R1, R2 resist;

[0339] VP1 Imaginary plane.

Claims

1. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component has higher moisture resistance than the insulating film of the second component. The insulating film of the second component has higher plasma resistance than the insulating film of the first component.

2. The elastic wave device according to claim 1, wherein: The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon nitride oxide film.

3. The elastic wave device according to claim 1, wherein: The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon oxide film.

4. The elastic wave device according to claim 1, wherein: The insulating film of the first component and the insulating film of the second component are silicon nitride oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

5. The elastic wave device according to claim 1, wherein: The insulating film of the first component is a silicon nitride oxide film, and the insulating film of the second component is a silicon oxide film.

6. The elastic wave device according to claim 1, wherein: The insulating film of the first component and the insulating film of the second component are aluminum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

7. The elastic wave device according to claim 1, wherein: The insulating film of the first component and the insulating film of the second component are titanium oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

8. The elastic wave device according to claim 1, wherein: The insulating film of the first component and the insulating film of the second component are tantalum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

9. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon nitride oxide film.

10. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component is a silicon nitride film, and the insulating film of the second component is a silicon oxide film.

11. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component and the insulating film of the second component are silicon nitride oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

12. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component is a silicon nitride oxide film, and the insulating film of the second component is a silicon oxide film.

13. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component and the insulating film of the second component are aluminum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

14. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least a portion of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component and the insulating film of the second component are titanium oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

15. An elastic wave device comprising: The piezoelectric layer has a first main surface and a second main surface that are opposite to each other in a first direction; at least one pair of electrodes provided on at least one of the first main surface and the second main surface; and a protective film covering at least any part of the pair of electrodes, The protective film includes an insulating film of a first component in contact with the pair of electrodes and an insulating film of a second component on the surface. The insulating film of the first component and the insulating film of the second component are tantalum oxide films, and the insulating film of the second component has a higher oxygen content than the insulating film of the first component.

16. The elastic wave device according to any one of claims 1 to 15, wherein: The pair of electrodes is an IDT electrode, which includes a first bus bar and a second bus bar opposite to each other in a second direction intersecting the first direction, at least one first electrode finger whose base end is connected to the first bus bar and extends along the second direction, and at least one second electrode finger whose base end is connected to the second bus bar and extends along the second direction.

17. The elastic wave device according to any one of claims 1 to 16, wherein: The elastic wave device further includes a support member having a support substrate. The piezoelectric layer is provided in the first direction of the support member, which is the thickness direction of the support substrate. The support member is provided with a space portion opened on the piezoelectric layer side in the first direction, At least a portion of the pair of electrodes overlaps with the space portion in a plan view as seen from the first direction.

18. The elastic wave device according to claim 17, wherein: The protective film in a region overlapping the space portion in the first direction includes an insulating film of the first component in contact with the pair of electrodes and an insulating film of the second component as a surface layer.

19. The elastic wave device according to claim 18, wherein: The protective film has: a portion including an insulating film of the first component and an insulating film of the second component; and a portion of the insulating film including only the second component, A portion including the insulating film of the first component and the insulating film of the second component overlaps the space portion in the first direction, In a portion including only the insulating film of the second component, the insulating film of the second component is in direct contact with the piezoelectric layer.

20. The elastic wave device according to claim 18, wherein The protective film in a region not overlapping with the space portion in the first direction includes only the insulating film of the second component, and the insulating film of the second component in the non-overlapping region is in direct contact with the piezoelectric layer.

21. The elastic wave device according to claim 17, wherein: The pair of electrodes is an IDT electrode, the IDT electrode including a first bus bar and a second bus bar facing each other in a second direction intersecting the first direction, at least one first electrode finger having a base end connected to the first bus bar and extending in the second direction, and at least one second electrode finger having a base end connected to the second bus bar and extending in the second direction, The first bus bar or the second bus bar is provided so as to overlap with a corner of the space portion in a plan view along the first direction.

22. The elastic wave device according to any one of claims 1 to 21, wherein: The Euler angles (φ, θ, ψ) of lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (1), formula (2) or formula (3), (0°±10°, 0°~20°, arbitrary ψ) …Formula (1) (0°±10°, 20°~80°, 0°~60° (1-(θ-50) 2 / 900) 1 / 2 ) or (0°±10°, 20°~80°, [180°-60° (1-(θ-50) 2 / 900) 1 / 2 ]~180°) …Formula (2) (0°±10°, [180°-30°(1-(ψ-90) 2 / 8100) 1 / 2 ]~180°, arbitrary ψ) …Formula (3).

23. The elastic wave device according to any one of claims 1 to 22, wherein: The pair of electrodes is an IDT electrode, the IDT electrode including a first bus bar and a second bus bar facing each other in a second direction intersecting the first direction, at least one first electrode finger having a base end connected to the first bus bar and extending in the second direction, and at least one second electrode finger having a base end connected to the second bus bar and extending in the second direction, When the film thickness of the piezoelectric layer is denoted by d and the center-to-center distance between the adjacent first electrode fingers and the second electrode fingers is denoted by p, d / p is equal to or less than 0.

5.

24. The elastic wave device according to claim 23, wherein: The d / p is 0.24 or less.

25. The elastic wave device according to any one of claims 1 to 24, wherein: The pair of electrodes is an IDT electrode, the IDT electrode including a first bus bar and a second bus bar facing each other in a second direction intersecting the first direction, at least one first electrode finger having a base end connected to the first bus bar and extending in the second direction, and at least one second electrode finger having a base end connected to the second bus bar and extending in the second direction, An area where adjacent first and second electrode fingers overlap when viewed in opposing directions is an excitation area, and when a metallization ratio of the first and second electrode fingers to the excitation area is MR, MR≤1.75(d / p)+0.075 is satisfied.

26. The elastic wave device according to any one of claims 1 to 25, wherein: The elastic wave device is configured to utilize thickness shear mode bulk waves.

27. The elastic wave device according to any one of claims 1 to 20, wherein: The elastic wave device is configured to utilize plate waves.

28. The elastic wave device according to any one of claims 1 to 15, wherein: The pair of electrodes includes a first electrode provided on the first principal surface of the piezoelectric layer, and a second electrode provided on the second principal surface.

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