Elastic wave devices, filters, and multiplexers

Abstract

The present invention provides an elastic wave device capable of suppressing deviations from the conditions for establishing a piston mode. The elastic wave device (100) comprises: a piezoelectric layer (15); a pair of comb-shaped electrodes (21) disposed on the piezoelectric layer (15), each having a plurality of electrode fingers (22), the intersection region (30) of the plurality of electrode fingers (22) intersecting each other comprising an edge region (32) located at the edge of the long side direction of the plurality of electrode fingers (22) and a central region (31) located inside the edge region (32); a first insulating film (16) covering the pair of comb-shaped electrodes (21) disposed on the piezoelectric layer (15); a load film (40) covering the front ends (27) of the plurality of electrode fingers (22) on the first insulating film (16) disposed in the edge region (32) and not disposed in the central region (31); and a second insulating film (17) covering the load film (40) disposed on the first insulating film (16).

Description

Technical Field

[0001] This invention relates to elastic wave devices, filters, and multiplexers. Background Technology

[0002] Elastic wave devices are used in high-frequency communication systems, such as mobile phones. As an elastic wave device, a known type is an elastic wave device having a pair of comb-shaped electrodes, each having multiple electrode fingers. It is known that a piston mode is achieved by making the sound velocity of the elastic wave in the edge region located at the long side edge of the electrode fingers in the intersection region of the pair of comb-shaped electrodes slower than the sound velocity of the elastic wave in the central region located further inward than the edge region, thereby suppressing spurious signals (e.g., Patent Documents 1-3).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-171054

[0004] Patent Document 2: International Publication No. 2018 / 116680

[0005] Patent Document 3: Japanese Patent Application Publication No. 2023-173756

[0006] There exists a situation where a load film is placed in the edge region to cover the tip of the electrode finger, but not in the central region, thereby causing the sound velocity of the elastic wave in the edge region to be slower than that in the central region. However, in this case, the condition for the piston mode to hold may sometimes deviate. Summary of the Invention

[0007] The present invention was made in view of the above-mentioned problems, and its purpose is to suppress deviations from the conditions for the piston mode to be established.

[0008] The present invention is an elastic wave device comprising: a piezoelectric layer; a pair of comb-shaped electrodes disposed on the piezoelectric layer, each having a plurality of electrode fingers, wherein the intersection region of the plurality of electrode fingers includes an edge region located at the edge of the long side of the plurality of electrode fingers and a central region located inside the edge region; a first insulating film covering the pair of comb-shaped electrodes and disposed on the piezoelectric layer; a load film covering the front ends of the plurality of electrode fingers and disposed in the edge region but not in the central region; and a second insulating film covering the load film and disposed on the first insulating film.

[0009] In the above structure, the first insulating film and the second insulating film may be configured such that the first insulating film and the second insulating film contain the same material in their main components.

[0010] In the above structure, the load film may be configured such that the material is contained in the main component, and the density of the load film is smaller than the density of the first insulating film and the second insulating film.

[0011] In the above structure, the material can be silicon oxide.

[0012] In the above structure, the thickness of the second insulating film can be greater than the thickness of the first insulating film.

[0013] The present invention is a filter comprising the above-described elastic wave device.

[0014] This invention is a multiplexer, which includes the aforementioned filter.

[0015] According to the present invention, it is possible to suppress deviations from the conditions that enable the piston mode. Attached Figure Description

[0016] Figure 1 (a) is a plan view of the elastic wave device of Example 1. Figure 1 (b) is along Figure 1 (a) is a cross-sectional view of line AA.

[0017] Figure 2 (a) to Figure 2 (d) is an exploded plan view of the elastic wave device of Example 1.

[0018] Figure 3 This is a graph showing the sound velocity of the elastic wave in Example 1.

[0019] Figure 4 (a) is a plan view of the elastic wave device of the comparative example. Figure 4 (b) is along Figure 4 (a) is a cross-sectional view of line AA.

[0020] Figure 5 (a) to Figure 5 (c) is a plan view showing another example of the loaded film of Example 1.

[0021] Figure 6 This is a plan view showing another example of the second insulating film of Embodiment 1.

[0022] Figure 7 (a) is the circuit diagram of the filter in Example 2. Figure 7 (b) is a circuit diagram of the duplexer of a modified example of Example 2.

[0023] Label Explanation

[0024] 10: Substrate; 15: Piezoelectric layer; 16: First insulating film; 17: Second insulating film; 20: IDT; 21: Comb electrode; 22: Electrode finger; 23: Dummy electrode finger; 24: Busbar; 25: Reflector; 26: Metal film; 27: Front end; 30: Cross region; 31: Central region; 32: Edge region; 33: Gap region; 34: Dummy region; 35: Busbar region; 40: Load film; 50: Transmitting filter; 51: Receiving filter; 100, 500: Elastic wave device; 200: Filter; 210: Duplexer. Detailed Implementation

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0026]

Example 1

[0027] Figure 1 (a) is a plan view of the elastic wave device 100 of Embodiment 1. Figure 1 (b) is along Figure 1 (a) is a cross-sectional view of line AA. Figure 2 (a) to Figure 2 (d) is an exploded plan view of the elastic wave device 100 of Embodiment 1. Figure 1 In (a), the illustrations of the first insulating film 16 and the second insulating film 17 are omitted for clarity. Figure 2 (a) is a plan view of the second insulating film 17. Figure 2 (b) is a plan view of the supported film 40. Figure 2 (c) is a plan view of the first insulating film 16. Figure 2 (d) is a planar view of the piezoelectric layer 15. The arrangement direction of the electrode fingers 22 is defined as the X direction, the direction of the long side of the electrode fingers 22 as the Y direction, and the stacking direction of the substrate 10 and the piezoelectric layer 15 as the Z direction. The X, Y, and Z directions do not necessarily correspond to the X-axis direction of the crystal orientation of the piezoelectric layer 15. In the case where the piezoelectric layer 15 is a piezoelectric layer that rotates Y to cut X and propagates, the X direction is the X-axis direction of the crystal orientation.

[0028] like Figure 1 of (a) Figure 1 (b) and Figure 2 (a) to Figure 2As shown in (d), a piezoelectric layer 15 is disposed on the substrate 10. The substrate 10 is, for example, a sapphire substrate, an alumina substrate, a silicon substrate, a spinel substrate, a crystal substrate, a quartz substrate, or a silicon carbide substrate. The piezoelectric layer 15 is, for example, a single-crystal lithium tantalate layer, a single-crystal lithium niobate layer, or a single-crystal quartz layer. The piezoelectric layer 15 may be, for example, a rotary Y-cut X-propagated lithium tantalate layer or a rotary Y-cut X-propagated lithium niobate layer, for example, a 30° to 50° rotary Y-cut X-propagated lithium tantalate layer. A single or multiple insulating layers of silicon oxide, alumina, and / or aluminum nitride may also be disposed between the substrate 10 and the piezoelectric layer 15.

[0029] An IDT (Interdigital Transducer) 20 and a reflector 25 are disposed on the piezoelectric layer 15. The IDT 20 has a pair of comb-shaped electrodes 21. The comb-shaped electrodes 21 have multiple electrode fingers 22, multiple dummy electrode fingers 23, and a busbar 24 connected to the multiple electrode fingers 22 and the multiple dummy electrode fingers 23. The front end of the electrode finger 22 of one comb-shaped electrode 21 is opposite to the front end of the dummy electrode finger 23 of the other comb-shaped electrode 21. The IDT 20 and the reflector 25 are formed of a metal film 26 on the piezoelectric layer 15. The metal film 26 is, for example, a film mainly composed of aluminum, copper, molybdenum, iridium, platinum, rhenium, rhodium, ruthenium, tantalum, or tungsten. The IDT 20 and the reflector 25 may also have a close-fitting film such as a titanium film or a chromium film between the metal film 26 and the piezoelectric layer 15.

[0030] The area where the electrode fingers 22 of a pair of comb electrodes 21 intersect is a cross region 30. The length of the cross region 30 in the Y direction is the opening length. The pair of comb electrodes 21 are positioned such that, in at least a portion of the cross region 30, the electrode fingers 22 are approximately alternately positioned in the X direction. In the cross region 30, the dominant mode elastic wave (surface acoustic wave) excited by the electrode fingers 22 propagates primarily in the X direction. The spacing of the electrode fingers 22 of one comb electrode 21 is approximately equal to the wavelength λ of the surface acoustic wave. The average spacing D of the plurality of electrode fingers 22 is approximately twice the wavelength λ. The average spacing D can be calculated by dividing the width of the IDT 20 in the X direction by the number of electrode fingers 22. The reflector 25 reflects the surface acoustic wave excited by the electrode fingers 22 of the IDT 20. Thus, the surface acoustic wave is confined within the cross region 30 of the IDT 20.

[0031] The cross region 30 has an edge region 32 located at the edge in the Y direction and a central region 31 located inside the edge region 32 in the Y direction. The edge region 32 can also be described as the region where the front end 27 of the electrode finger 22 in the cross region 30 is located. The region between the front end of the electrode finger 22 of one comb electrode 21 and the front end of the dummy electrode finger 23 of the other comb electrode 21 is the gap region 33. That is, the gap region 33 is the region located in front of the front end of the electrode finger 22. The region where the dummy electrode finger 23 is located is the dummy region 34. The region where the busbar 24 is located is the busbar region 35.

[0032] Alternatively, the dummy electrode fingers 23 may not be present. In this case, the tip of the electrode finger 22 of one comb electrode 21 is opposite to the busbar 24 of the other comb electrode 21. Therefore, the area between the tip of the electrode finger 22 of one comb electrode 21 and the busbar 24 of the other comb electrode 21 is the gap region 33.

[0033] A first insulating film 16 is formed on the piezoelectric layer 15 such that it covers the IDT 20 and the reflector 25. The first insulating film 16 is formed over the entire surface of the piezoelectric layer 15. The first insulating film 16 is, for example, an insulating film with silicon oxide as the main component, such as a silicon oxide (SiO2) film with or without additives. The thickness of the first insulating film 16 is, for example, 5 nm to 10 nm.

[0034] A load film 40 is provided on the first insulating film 16, extending from the edge region 32 to a portion of the gap region 33, covering the front end 27 of the electrode finger 22. The load film 40 is, for example, arranged in a strip shape along the X direction. The load film 40 is not provided in the central region 31, the remaining portion of the gap region 33, the dummy region 34, or the busbar region 35. The load film 40 is, for example, an insulating film primarily composed of silicon oxide, such as a silicon oxide (SiO2) film with or without additives. The thickness of the load film 40 is, for example, greater than the thicknesses of the first insulating film 16 and the second insulating film 17, for example, 20 nm to 80 nm. The density of the load film 40 is less than the density of the first insulating film 16.

[0035] A second insulating film 17 is disposed on the first insulating film 16 in a manner that covers the load film 40. The second insulating film 17, for example, is disposed over the entire surface of the first insulating film 16. The second insulating film 17 is, for example, an insulating film with silicon oxide as its main component, such as a silicon oxide (SiO2) film with or without additives. The thickness of the second insulating film 17 is, for example, less than the thickness of the load film 40. The thickness of the second insulating film 17 is, for example, greater than the thickness of the first insulating film 16, for example, 10 nm to 15 nm. The density of the second insulating film 17 is greater than the density of the load film 40.

[0036] Thus, in Example 1, the first insulating film 16, the load film 40, and the second insulating film 17 contain the same material (silicon oxide) in their main components, and the density of the load film 40 is lower than that of the first insulating film 16 and the second insulating film 17. The load film 40 is covered by the first insulating film 16 and the second insulating film 17, which have a higher density than the load film 40. The load film 40 is in contact with the first insulating film 16 and the second insulating film 17.

[0037] Here, "a certain membrane is mainly composed of a certain element" allows for the presence of desired or undesirable impurities other than the main component in the membrane. When a certain element is the main component in a membrane, its concentration is, for example, 50 atomic percent or more, or 80 atomic percent or more. In the case where two or more elements are the main components, such as silicon oxide, the combined concentration of the two or more elements is 50 atomic percent or more, 80 atomic percent or more, or 90 atomic percent or more. Each of the two or more elements may have a concentration of 10 atomic percent or more, or 20 atomic percent or more.

[0038] [Speed ​​of sound of elastic waves]

[0039] Figure 3 This is a graph showing the sound velocity of the elastic wave in Example 1. Figure 3 As shown, because a load film 40 is provided in the edge region 32, the sound speed of the elastic wave propagating in the edge region 32 is slower than that of the elastic wave propagating in the central region 31. Compared to the central region 31, the region in the gap region 33 without the load film 40 has fewer electrode fingers 22, therefore the sound speed of the propagating elastic wave there is faster than that in the central region 31. For example, the sound speed of the elastic wave propagating in the region in the gap region 33 with the load film 40 is slower than that in the central region 31. The sound speed of the elastic wave propagating in the dummy region 34 is approximately the same as that in the central region 31. For example, the sound speed of the elastic wave propagating in the busbar region 35 is faster than that in the central region 31. By setting the regions in the edge region 32 and the gap region 33 where the load membrane 40 is provided as low-sound-speed regions where the sound speed of the elastic wave is slower than that of the elastic wave in the central region 31, and setting the regions in the gap region 33 where the load membrane 40 is not provided as high-sound-speed regions where the sound speed of the elastic wave is faster than that of the elastic wave in the central region 31, the piston mode can be realized.

[0040] [Manufacturing Method]

[0041] The manufacturing method of the elastic wave device 100 of Example 1 will be described. First, after bonding the piezoelectric layer 15 to the substrate 10 using, for example, a surface activation method, the piezoelectric layer 15 is polished to a desired thickness using, for example, CMP (Chemical Mechanical Polishing). Next, a metal film 26 is formed on the piezoelectric layer 15, and then the metal film 26 is patterned into a desired shape. Thus, an IDT 20 and a reflector 25 are formed on the piezoelectric layer 15. The metal film 26 is formed, for example, using sputtering, CVD (Chemical Vapor Deposition), or vacuum evaporation. The patterning of the metal film 26 is performed, for example, using photolithography and etching.

[0042] Next, a first insulating film 16 is formed on the piezoelectric layer 15 in such a way that it covers the IDT 20 and the reflector 25. The first insulating film 16 is formed, for example, by sputtering.

[0043] Next, a load film 40 covering the leading end portion 27 of the electrode finger 22 is formed on the first insulating film 16 from a portion of the edge region 32 to the gap region 33. The load film 40 is formed, for example, by forming a mask layer with openings in a portion of the edge region 32 and the gap region 33 on the first insulating film 16, then forming the load film 40 using the mask layer as a mask, and subsequently removing the mask layer. The load film 40 is not formed only in the edge region 32, but rather from the edge region 32 to the gap region 33, for alignment accuracy. A photoresist is used, for example, as the mask layer. The load film 40 is formed, for example, using vacuum evaporation.

[0044] Next, a second insulating film 17 is formed on the first insulating film 16 in a manner that covers the load film 40. The second insulating film 17 is formed, for example, by sputtering. Through the above, the elastic wave device 100 of Embodiment 1 is formed.

[0045] Thus, a silicon oxide film is formed using vacuum evaporation to form a load film 40, thereby achieving a low-density load film 40. A silicon oxide film is then formed using sputtering to form a first insulating film 16 and a second insulating film 17, thereby achieving a high-density first insulating film 16 and a second insulating film 17 with good film quality. Therefore, the density of the load film 40 is lower than the density of the first insulating film 16 and the second insulating film 17.

[0046] [Comparative Example]

[0047] Figure 4 (a) is a plan view of the comparative example elastic wave device 500. Figure 4 (b) is along Figure 4 A cross-sectional view of line AA in (a). Figure 4(a) and Figure 4 As shown in (b), in the comparative example, a second insulating film covering the load film 40 is not provided on the first insulating film 16. The other structures are the same as in Example 1, so the description is omitted.

[0048] If a second insulating film covering the load film 40 is not provided, as in the comparative example, moisture may seep into the load film 40 over time during and / or after manufacturing, causing a change in weight. To achieve the piston mode, the weight is adjusted by changing the film thickness of the load film 40; however, if the weight of the load film 40 changes, it may sometimes deviate from the conditions for the piston mode to be established.

[0049] In Example 1, as Figure 1 (b) and Figure 2 (a) to Figure 2 As in (c), the load film 40 is covered by the first insulating film 16 and the second insulating film 17. Therefore, moisture infiltration into the load film 40 can be suppressed both during manufacturing and over time. This also suppresses changes in the weight of the load film 40 and prevents deviations from the conditions required for the piston mode to be established.

[0050] Furthermore, to achieve the piston mode, the weight is adjusted by changing the thickness of the load film 40. However, if the thickness of the load film 40 increases, the film stress generated on the load film 40 increases. The load film 40 is only provided in the edge region 32 of the intersection region 30, not in the central region 31. Therefore, the contact area between the load film 40 and the first insulating film 16 is small. Therefore, if the film stress generated on the load film 40 increases, film peeling is more likely to occur on the load film 40. However, in Embodiment 1, the second insulating film 17 is provided to cover the load film 40, thus suppressing film peeling on the load film 40. The thickness of the load film 40 is, for example, more than 3 times, more than 7 times, or more than 10 times that of the first insulating film 16.

[0051] Furthermore, in Example 1, the first insulating film 16 and the second insulating film 17 contain the same material (silicon oxide) in their main components. This improves the adhesion between the first insulating film 16 and the second insulating film 17, thereby further suppressing moisture penetration into the load film 40. The first insulating film 16 and the second insulating film 17 are not limited to containing silicon oxide in their main components; they may also contain other insulating materials such as silicon nitride.

[0052] Furthermore, in Example 1, the supporting film 40 contains the same material (silicon oxide) as the first insulating film 16 and the second insulating film 17 in its main component, but the density of the supporting film 40 is lower than that of the first insulating film 16 and the second insulating film 17. To achieve the piston mode, the film thickness of the supporting film 40 is adjusted to control the weight. However, if a film with a high density is used for the supporting film 40, the change in sound velocity per unit thickness is large, which is not preferable from the perspective of achieving the piston mode. Therefore, in Example 1, a silicon oxide film with a lower density than the first insulating film 16 and the second insulating film 17 is used for the supporting film 40. In this case, although there is a concern that moisture can easily penetrate the supporting film 40, by covering the supporting film 40 with the high-density first insulating film 16 and the second insulating film 17, moisture penetration into the supporting film 40 can be suppressed. This suppresses changes in the weight of the supporting film 40 and prevents deviations from the conditions for the piston mode from being established. The densities of the first insulating film 16, the load film 40, and the second insulating film 17 can be determined, for example, by using the X-ray reflectance method (XRR method).

[0053] When the first insulating film 16, the load film 40, and the second insulating film 17 contain the same material (e.g., silicon oxide) in their main components, from the viewpoint of achieving a piston mode, the ratio A (A = (D1-D2) / D1) of the difference between the density D1 of the first insulating film 16 and the density D2 of the load film 40 relative to the density D1 of the first insulating film 16 is preferably 4% or more, more preferably 6% or more, and even more preferably 8% or more. Similarly, the ratio B (B = (D3-D2) / D3) of the difference between the density D3 of the second insulating film 17 and the density D2 of the load film 40 relative to the density D3 of the second insulating film 17 is preferably 4% or more, more preferably 6% or more, and even more preferably 8% or more. From the perspective of the film quality of the load film 40, the ratios A and B are preferably 15% or less, more preferably 13% or less, and even more preferably 11% or less.

[0054] Furthermore, by including the same material as the first insulating film 16 and the second insulating film 17 in its main component, the adhesion between the load film 40 and the first insulating film 16 and the second insulating film 17 is improved. Therefore, moisture absorption by the load film 40 can be further suppressed. Moreover, the coefficients of linear expansion of the first insulating film 16, the load film 40, and the second insulating film 17 are approximately the same, thus reducing the stress generated in each film. Furthermore, since the first insulating film 16, the load film 40, and the second insulating film 17 are all insulating films, leakage current generated between adjacent electrode fingers 22 can be suppressed.

[0055] Furthermore, in Example 1, the first insulating film 16, the load film 40, and the second insulating film 17 all contain silicon oxide in their main components. This allows for a situation where the first insulating film 16, the load film 40, and the second insulating film 17 all contain silicon oxide in their main components.

[0056] Furthermore, in Example 1, the thickness of the second insulating film 17 is greater than the thickness of the first insulating film 16. This further suppresses moisture absorption by the load film 40 and further suppresses peeling of the load film 40. The thickness of the second insulating film 17 can be 1.2 times or more, 1.5 times or more, or 1.8 times or more of the thickness of the first insulating film 16. It is believed that if the second insulating film 17 is too thick, it will adversely affect the realization of the piston mode; therefore, the thickness of the second insulating film 17 is preferably 2.5 times or less, more preferably 2.3 times or less, and even more preferably 2.0 times or less of the thickness of the first insulating film 16.

[0057] Furthermore, in Embodiment 1, the load film 40 is disposed from the edge region 32 to the gap region 33 located in front of the tip of the electrode finger 22. When the load film 40 is disposed from the edge region 32 to the gap region 33 in a manner that covers the tip of the electrode finger 22, if the film stress generated in the load film 40 increases, film peeling of the load film 40 is likely to occur. However, even in such a case, since the load film 40 is covered by the second insulating film 17, film peeling of the load film 40 can be suppressed.

[0058] Alternatively, the first insulating film 16 and the second insulating film 17 may contain different materials in their main components. The supporting film 40 may also be an insulating film or a metal film made of a material different from at least one of the first insulating film 16 and the second insulating film 17. For example, the supporting film 40 may be an insulating film with silicon oxide, tantalum oxide, or niobium oxide as its main components, or a metal film with aluminum or titanium as its main components. When the supporting film 40 is a metal film, although there is a possibility of increased corrosion and weight change after moisture infiltration, the covering of the supporting film 40 by the first insulating film 16 and the second insulating film 17 can inhibit moisture infiltration and thus suppress corrosion.

[0059] [Variation Example]

[0060] Figure 5 (a) to Figure 5 (c) is a plan view showing another example of the supported film 40 of Example 1. Alternatively, as... Figure 5 (a) to Figure 5 As shown in (c), the load film 40 is distributed in the edge region 32 such that it covers the front end portion 27 of the electrode finger 22. In this case, it can be as follows: Figure 5As in (a), the following situation applies: the length of the loaded film 40 in the X direction is approximately the same as the length of the electrode finger 22 in the X direction. Alternatively, it can be as follows: Figure 5 As in (b), the situation is as follows: the X-direction end of the load film 40 is located between it and the adjacent electrode finger 22, and the load film 40 does not overlap with the adjacent electrode finger 22. Alternatively, it can be as follows: Figure 5 As in (c), the situation is as follows: the X-direction end of the load film 40 overlaps with or partially overlaps with the end of the adjacent electrode finger 22. Regarding the planar shape of the load film 40 as observed from the +Z direction, it can be described as follows... Figure 5 (a) can be an oval or round shape with rounded corners, or it can be like... Figure 5 (b) and Figure 5 (c) is a rectangular shape.

[0061] Figure 6 This is a plan view showing another example of the second insulating film 17 of Embodiment 1. Figure 6 In the diagram, to make it clearer, the second insulating film 17 is marked with a shaded line. It can be seen as follows... Figure 6 As shown, the second insulating film 17 is configured as a strip extending along the Y direction, covering the electrode finger 22 and the dummy electrode finger 23.

[0062]

Example 2

[0063] Figure 7 (a) is a circuit diagram of filter 200 in Example 2. Figure 7 As shown in (a), one or more series resonators S1 to S4 are connected in series between the input terminal Tin and the output terminal Tout. One or more parallel resonators P1 to P3 are connected in parallel between the input terminal Tin and the output terminal Tout. At least one of the series resonators S1 to S4 and the parallel resonators P1 to P3 can use the elastic wave device of Embodiment 1 and its modifications. The number of series resonators and parallel resonators can be appropriately set. A trapezoidal filter is shown as a filter, but the filter can also be a multimode filter.

[0064] Figure 7 (b) is a circuit diagram of the duplexer 210 of a modified example of Embodiment 2. Figure 7As shown in (b), a transmit filter 50 is connected between the common terminal Ant and the transmit terminal Tx. A receive filter 51 is connected between the common terminal Ant and the receive terminal Rx. The transmit filter 50 allows signals in the transmit band of the high-frequency signal input from the transmit terminal Tx to be transmitted to the common terminal Ant as transmit signals, and suppresses signals of other frequencies. The receive filter 51 allows signals in the receive band of the high-frequency signal input from the common terminal Ant to be received to the receive terminal Rx as receive signals, and suppresses signals of other frequencies. At least one of the transmit filter 50 and the receive filter 51 can be the filter of Embodiment 2. A duplexer is exemplified as a multiplexer, but a tripplexer or a quadplexer can also be used.

[0065] The embodiments of the present invention have been described in detail above, but the present invention is not limited to this specific embodiment and various modifications and alterations can be made within the scope of the spirit of the present invention as described in the claims.

Claims

1. An elastic wave device, comprising: piezoelectric layer; A pair of comb-shaped electrodes are disposed on the piezoelectric layer, each having multiple electrode fingers. The intersection region of the multiple electrode fingers includes an edge region located at the edge of the long side of the multiple electrode fingers and a central region located inside the edge region. A first insulating film is disposed on the piezoelectric layer, covering the pair of comb-shaped electrodes; A load film is provided on the first insulating film, covering the front ends of the plurality of electrode fingers and disposed in the edge region, but not in the central region; as well as A second insulating film is disposed on the first insulating film, covering the load film.

2. The elastic wave device according to claim 1, wherein, The first insulating film and the second insulating film contain the same material in their main components.

3. The elastic wave device according to claim 2, wherein, The loaded film contains the material in its main components, and the density of the loaded film is less than that of the first insulating film and the second insulating film.

4. The elastic wave device according to claim 2 or 3, wherein, The material is silicon dioxide.

5. The elastic wave device according to claim 1 or 2, wherein, The thickness of the second insulating film is greater than the thickness of the first insulating film.

6. A filter comprising the elastic wave device of claim 1 or 2.

7. A multiplexer comprising the filter of claim 6.

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