JPH1056354A - Surface acoustic wave filter and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make high the frequency of a band-pass filter which utilizes a surface acoustic wave(SAW). SOLUTION: Metal layers 15 of Au and piezoelectric layers 12 of ZnO are laminated by turns and the end parts of alternate metal plates 15 are connected to constitute an inter-digital electrode 13. At an inter-digital electrode part 16, a couple of inter-digital electrodes 13 mesh each other. A SAW filter 101 has an inter-digital electrode part 16, a SAW propagation part 14, and the other inter-digital electrode part 16 laminated in order on a glass substrate 11. The metal layers 15 and piezoelectric layers 12 are, for example, 0.01μm thick respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave (hereinafter abbreviated as SAW) filter which is a kind of high frequency filter.

[0002]

2. Description of the Related Art A SAW filter is used as a band-pass filter in combination with another dielectric filter, a laminated ceramics filter, or the like according to the application and purpose. In recent years, these band-pass filters have been increased in frequency for mobile communications,
Miniaturization is required. In the current mobile communications field,
PDC (Personal Digital Cellular) method is 800M
Hz and 1.5 GHz, PHS (Personal Handyhone S
ystem) system is assigned to the frequency band of 1.895 to 1.918 GHz and used. In the future,
These filters have become higher in frequency and smaller in size, and
It would be necessary to develop a Hz bandpass filter.

FIG. 11 is a perspective view of an example of a conventional SAW filter 100. As shown in FIG. On the surface of the piezoelectric layer 2 formed on the substrate 1, two pairs of intricate comb-teeth electrodes 3 are formed. One pair of comb electrodes 3 is on the input side, and the other pair of comb electrodes 3 is on the output side. The SAW propagation section 4 is between the two pairs of comb electrodes 3. The wave input to the input-side comb-teeth electrode 3 propagates through the SAW propagation unit 4, and only the wave selected by the interval between the comb-teeth electrodes is output from the output-side comb-teeth electrode 3.

[0004]

In the SAW filter, the center frequency of the band pass is f ₀ , the center distance of the comb teeth is 2l ₀ ,
Assuming that the propagation speed of the SAW is v ₀ , the following relationship holds: v ₀ = f ₀ × 4l ₀ (1) From this equation, the following means can be considered to manufacture a high-frequency SAW filter.

[0005] to narrow the comb teeth interval l _0. A material having a high SAW propagation speed v ₀ is used. However, lithium niobate (LiNbO ₃ ) and lithium tantalate (Li
TaO ₃ ) A material having superior characteristics compared to a single crystal and having a high SAW propagation speed has not been found at present. Therefore, in order to manufacture a filter in the GHz band, a comb tooth interval l ₀
Is generally adopted.

[0006] Such a comb-shaped electrode is manufactured by using a photolithography technique. The minimum line width of the photolithography technique is substantially equal to the wavelength of the transfer light, and for example, an accuracy of about 0.05 μm is obtained by using electron beam exposure. However, mass production using this requires an electron beam exposure apparatus with a high throughput, and requires a large investment.

[0007] When a comb is formed with a line width of 0.05 μm as described above and used as a filter, transmission and reception in the 20 GHz band becomes possible. However, this requires an expensive electron beam exposure apparatus, and it is not possible to manufacture a filter satisfying the requirements of high-frequency millimeter-wave or quasi-millimeter-wave devices by photolithography using electron beam exposure. There is also an X-ray exposure method of short wavelength SOR (synchrotron exposure radiation), but it is still in the development stage and requires large-scale equipment.

In view of the above problems, an object of the present invention is to provide a SAW filter suitable for high frequency and easy to manufacture, and a method for manufacturing the same.

[0009]

In order to solve the above problems, a surface acoustic wave filter according to the present invention has a shape in which a pair of comb teeth in which a metal layer and a piezoelectric layer are alternately stacked on an insulating substrate are intertwined with each other. A comb electrode portion, a surface acoustic wave propagating portion formed thereon, and a comb electrode portion similar to the above formed thereon are further formed thereon.

[0010] A metal, a piezoelectric film, a metal, and a piezoelectric film are alternately deposited on a substrate to form comb teeth in the vertical direction. Since the deposition accuracy of the thin film is high and the deposition of a film having a thickness of 0.01 μm is also possible, the comb tooth spacing that determines the limit of the SAW filter is
0.05 which is the limit of current ordinary photolithography
Dimensions of μm or less can be realized. That is, a high-frequency SAW filter with a small comb tooth spacing, and thus a high frequency, can be formed.
The thickness of about 0.01 μm can be measured with a surface roughness meter, an atomic force microscope (AFM) or an ellipsometer.

In particular, it is assumed that the piezoelectric layer and the surface acoustic wave propagation layer are made of a c-axis oriented polycrystalline film of zinc oxide (ZnO) or aluminum nitride (AlN). When the piezoelectric material is thinned, the piezoelectric characteristics cannot be obtained unless the thin film is oriented or subjected to a polarization treatment after the thin film is formed. Therefore, it is preferable to use zinc oxide, aluminum nitride, and titanium oxide lead zirconate (hereinafter referred to as PZT), which can obtain orientation, as the piezoelectric substance.

In addition, with the above structure, the high speed S
The longitudinal wave of AW can be used, and the speed of SAW can be increased. Table 1 shows longitudinal waves in ZnO and AlN single crystals,
The difference of shear wave speed is described.

[0013]

[Table 1] From the above equation (1), it can be seen that even with the same comb tooth spacing (in this case, wavelength), propagation of a higher frequency wave using a transverse wave is possible.

That is, the SAW filter of the present invention can be used at a frequency two to three times higher than that of the conventional one even if the same pressure electrode body layer is used. The metal layer is made of gold (Au),
Composite film of gold / titanium (Au / Ti), aluminum (A
1) or platinum (Pt). On these metal layers, ZnO and AlN tend to be c-axis oriented.

Since the piezoelectric layer and the surface acoustic wave propagating layer are made of lead zirconate titanate (PZT), which becomes a polycrystalline film of c-axis orientation on Pt, the metal layer is preferably made of Pt. The substrate is
It shall be silicon or glass. These have a smooth surface and are easily available, and the metal film formed thereon has excellent crystal axis orientation.

For the same reason, a c-plane or an R-plane of sapphire is used as a substrate, and gold / chromium (A
u / Cr) composite film can also be used. It is preferable that a terminal electrode connected to the comb electrode is provided on the upper surface of the laminate. By doing so, it is possible to increase the size of the electrode, and if it is on the upper surface, the lead can be easily bonded.

It is assumed that the metal layers laminated with the piezoelectric layer interposed therebetween are connected by side electrodes formed on the side surfaces to form a comb electrode. By doing so, the number of photolithography and the number of masks at the time of forming the comb electrode portion can be reduced.
The side surfaces are preferably inclined at an obtuse angle with respect to the surface of the laminate.

In this case, the adhesive strength of the side electrode is increased, the contact area between the metal layer and the side electrode is increased, and the formation of the comb electrode is ensured. As a method for manufacturing a surface acoustic wave filter having a comb-teeth electrode portion in which a pair of comb teeth in which a metal layer and a piezoelectric layer are alternately stacked on an insulating substrate is formed by photo-forming on a first film deposited After applying a resist, forming a pattern on the first film, depositing a second film, the photoresist is removed, and the removed portion of the first film is filled with the second film.

If such a lift-off method is used, the number of times of photolithography can be reduced to half as compared with a method of forming each by photolithography.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A SAW filter according to the present invention has a comb-shaped electrode formed by alternately laminating a metal layer and a piezoelectric layer on a substrate. For this reason, a dimension smaller than the limit of the current photolithography can be realized as a comb tooth interval that determines the limit of the SAW filter, and thus the SAW filter is suitable for a high frequency.

In addition, since the SAW uses a longitudinal wave faster than a transverse wave, the SAW can be calculated from the above equation (1).
The speed of W can be increased, and the SAW filter is more suitable for high frequencies. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a SAW filter 101 according to a first embodiment of the present invention.

Au metal layer 15 and ZnO piezoelectric layer 12
Are alternately laminated, and every other metal layer 15 is connected at an end to form a comb electrode 13. Comb electrode section 16
Has a shape in which a pair of comb electrodes 13 are engaged with each other. In the SAW filter 101, a comb-tooth electrode portion 16, a ZnO SAW propagation portion 14, and another comb-tooth electrode portion 16 are laminated on a glass substrate 11 in this order.
The thickness of the SAW propagation section 14 is 1 μm, and the thicknesses of the metal layer 15 and the piezoelectric layer 12 are, for example, 0.01 μm, respectively.
The thickness was measured by AFM. The width and depth of the SAW filter 101 are about 0.2 mm. Note that the thickness of the metal layer 15 and the thickness of the piezoelectric layer 12 do not necessarily have to be the same.

FIGS. 3 (a) to 3 (g), 4 (a) to 4 (f) and FIG. 6 are cross-sectional views showing some steps for explaining a method of manufacturing the SAW filter of FIG. An Au layer 15a to be a metal layer is deposited on the glass substrate 11 by high frequency sputtering [FIG. 3 (a)]. This Au
The layer 15a has a (111) -oriented surface.

A photoresist 20a is applied, and a pattern of the Au layer 15a is formed using a first photomask [FIG. 2 (b)]. However, the photoresist 20a does not peel off immediately. ZnO which becomes the piezoelectric layer 12 thereon
The layer 12a is deposited by high-frequency sputtering [FIG.

Next, the photoresist 20a is peeled off, and the ZnO layer 12a thereon is lifted off (FIG. 2D). The ZnO layer 12 is located between the patterns of the Au layer 15a.
is filled, and a substantially flat surface is obtained. Z on it
An nO layer 12b is deposited by high frequency sputtering [FIG. The ZnO layer 12b is a film having good c-axis orientation.

A photoresist 20b is applied, and a pattern of the ZnO layer 12b is formed using a second photomask [FIG. However, the photoresist 20b does not peel off immediately. An Au layer 15b is deposited thereon by high frequency sputtering, the photoresist 20b is peeled off, and the Au layer 15b thereon is lifted off [FIG. The Au layer 15 is placed between the patterns of the ZnO layer 12b.
b is buried and a substantially flat surface is obtained.

Au layer 15c by high frequency sputtering
Is deposited, a photoresist 20c is applied thereon, and a pattern of the Au layer 15c is formed using a third photomask [FIG. 4A]. However, the photoresist 20
c does not peel off immediately. A ZnO layer 12c is deposited thereon by high frequency sputtering, and a photoresist 2
0c is peeled off, and the ZnO layer 12c thereon is lifted off [FIG. Zn between the patterns of the Au layer 15c
The O layer 12c is buried, and a substantially flat surface is obtained.

A ZnO layer 12d to be a piezoelectric layer is deposited thereon by sputtering, and a photoresist 20d
And using a second photomask, a ZnO layer 1
A 2d pattern is formed [FIG. However, the photoresist 20d does not peel off immediately. Au on top
The layer 15d is deposited by high-frequency sputtering, the photoresist 20d is stripped, and the Au layer 15d thereon is lifted off (FIG. 2D). The Au layer 15d is buried between the patterns of the ZnO layer 12d, and a substantially flat surface is obtained.

Au layer 15e by high frequency sputtering
Is deposited, a photoresist 20e is applied, and a pattern of the Au layer 15e is formed using the first photomask [FIG. However, the photoresist 20e does not peel off immediately. A ZnO layer 12e is deposited thereon by high-frequency sputtering, the photoresist 20e is peeled off, and the ZnO layer 12e thereon is lifted off [FIG. The ZnO layer 12 is located between the patterns of the Au layer 15e.
e is filled, and a substantially flat surface is obtained.

By using the lift-off method as described above, the number of times of photolithography can be reduced to half as compared with a method of forming each by photolithography. While changing the photomask, the deposition of both the Au layer 15 and the ZnO layer 12 is repeated to form a complicated comb-tooth electrode portion 16. Further, the SAW propagation section 14 is laminated on the comb electrode section 16 to form another comb electrode section 16 (FIG. 6). The minimum number of the ZnO layers of the comb-teeth electrode section 16 is four, but if ten or more layers are stacked, the propagation characteristics are improved.

In FIG. 6, if a portion corresponding to the back of the comb-tooth electrode 13 is cut by a dicer to form a chip, FIG.
Is obtained. In the steps described above, the ZnO layer thickness (comb-tooth electrode interval) is set to 0.0
Filters from 1 μm to 0.1 μm were made. In the SAW filter 101 shown in FIG. 1, an example is shown in which the metal layer 15 laminated on the end face is exposed, but it is not necessary to expose the metal layer 15 and this face may be covered with an insulator. In addition, it can be prevented from being exposed by devising a pattern. FIG. 2 is a perspective view of a SAW filter 102 according to a second embodiment of the present invention.

On both sides of the SAW propagation portion 24 made of ZnO, there are comb-teeth-shaped comb-teeth electrode portions 26a and 26b in which Au layers 25 and ZnO layers 22 are alternately laminated and intertwined with each other. The ends of the layer 25 are connected to form a comb electrode 23. The difference from the first embodiment shown in FIG. 1 is that the end of the laminated Au layer 25 is formed on the side electrode 27 formed on the side surface.
And a comb electrode 23, and a side electrode 27 is extended to the upper surface of the SAW filter and a terminal electrode 28 is provided. The Au layer 25 of the upper comb-tooth electrode portion 26b is connected to the side electrode 27 on the near side.
Although it is not in contact with the terminal electrode 28, it is in contact with the side electrode 27 at the back, and is also extended to the upper surface, and the terminal electrode 28 is provided. 21 is a glass substrate, and 29 is a protective film of a silicon oxide film.

FIGS. 5A to 5H and FIG.
(A), (b) is sectional drawing of some processes for demonstrating the manufacturing method of the SAW filter of FIG. An Au layer 25a is deposited on the glass substrate by sputtering [FIG. 5 (a)]. The Au layer 25a becomes a (111) oriented film. A photoresist 30a is applied, and a pattern of the Au layer 25a is formed using a first photomask [FIG. However, the photoresist 30a does not peel off.

A ZnO layer 22a is deposited thereon by sputtering [FIG. 3 (c)]. Next, the photoresist 30a is peeled off, and the ZnO layer 22a thereon is lifted off [FIG. The ZnO layer 22a is buried between the patterns of the Au layer 25a, and a substantially flat surface is obtained. A ZnO layer 22b serving as a piezoelectric body is deposited thereon by sputtering [FIG. ZnO layer 22b
Is a film having good c-axis orientation.

An Au layer 25b is deposited by sputtering, a photoresist 30b is applied, and a pattern of the Au layer 25b is formed using a second photomask [FIG. However, the photoresist 30b does not peel off. A ZnO layer 22c is deposited thereon by sputtering, and the photoresist 30b is peeled off.
The nO layer 22c is lifted off [FIG. The ZnO layer 22c is buried between the patterns of the Au layer 25b, and a substantially flat surface is obtained.

The deposition of these two layers is repeated while changing the photomask to form an intricate comb-tooth electrode portion 26a. Further, ZnO to be the SAW propagation section 24 is laminated, and the other comb electrode section 26b and the uppermost silicon oxide layer 29 are formed (FIG. 7A). In the figure, the Au layer 25 of the upper comb electrode portion 26b does not reach the planned dicing portion indicated by the dotted line, but reaches the planned dicing portion in another section in the depth direction of the paper.

A groove 50 reaching the glass substrate 21 is formed from the laminated surface by a dicer, and three layers of Au / Ti / Ni are vapor-deposited on the upper surface and the inner surface of the groove 50 by sputtering to form a side electrode 27. Au layer 25
Are connected to form a comb-tooth electrode 23, and a pattern is formed by photolithography to form a terminal electrode 28 [FIG. When depositing three layers of Au / Ti / Ni on the inner surface of the groove 50, the glass substrate 21 may be tilted and rotated.

In the figure, the side electrode 27 is connected only to the metal layer 25 of the lower comb-teeth electrode portion 26a, but the metal layer 25 of the upper comb-teeth electrode 26b is formed on another side formed on the back side of the drawing. It is connected to the side electrode 27. In this manner, each of the comb-tooth electrodes 23 of the upper and lower comb-tooth electrode portions 26a, 26b can be taken out from the upper surface. Thereafter, the glass substrate 21 is cut into a predetermined size and formed into chips, whereby the SAW filter 102 is completed.

Through the steps described above, a SAW filter having a ZnO layer thickness (comb-tooth electrode interval) of 0.01 μm to 0.1 μm was manufactured. FIG. 8 is a graph showing propagation loss characteristics of a prototype SAW filter. The horizontal axis represents frequency, and the vertical axis represents propagation loss. It can be seen that it can be used at 30 GHz even if the propagation loss is within a practical 20 dB. This is because the SAW filter of the present invention has a multi-layer structure to realize a comb-tooth electrode spacing of 0.01 μm, which exceeds the limit of transfer light by photolithography, and utilizes longitudinal vibration of a piezoelectric body. It depends.

In the case of the present invention, the critical dimension of the interval between the comb teeth is a film thickness at which the piezoelectric layer exhibits piezoelectricity, which is generally about the same as the particle diameter of the thin film. Therefore, if a flat piezoelectric layer having a small particle size is formed, a SAW filter with a higher frequency can be manufactured.
In addition, if a flat particle shape can be obtained, SAW of higher frequency can be achieved.
A filter could be made. As a piezoelectric material, Zn
The same effect can be obtained by using AlN instead of O. Also, instead of Au, Au / Ti, Al,
The same effect can be obtained by using Pt. When PZT is used as the piezoelectric body, the metal layer exhibits c-axis orientation only when the metal layer is Pt (111). Therefore, in the case of PZT, Pt is preferably used as the metal layer.

In the SAW filter of the embodiment 102, since the comb electrodes 23 are formed by the side electrodes 27, the number of times of photolithography is half that of the SAW filter of the embodiment 101, and the SAW filter is easy to manufacture. Filter. Further, the side electrode 27 is extended to the upper surface to form a large terminal electrode 28, so that assembly is easy. Third Embodiment FIG. 9 is a perspective view of a SAW filter 103 according to a third embodiment of the present invention.

One of the two sets of comb electrode portions 36 constituting the SAW filter can be common. In the SAW filter 103 according to the third embodiment, the side electrode 37 on the front side is connected to one of the comb electrodes 33 of the upper and lower comb electrodes 36.
, And the side electrode 37 on the back side is the extraction of the other comb electrode. The metal layer that is not exposed is sandwiched between the metal layers 35 that are exposed on the side surfaces. Thus, the terminal electrode 3
8 may be three, and the side electrodes 37 may be formed on different side surfaces, respectively. Fourth Embodiment FIG. 10 is a perspective view of a SAW filter 104 according to a fourth embodiment of the present invention.

The point that the laminated Au layer 45 is formed as the comb-teeth electrode 43 by the side electrode 47 formed on the side surface,
The point that the side electrode 47 extends to the upper surface of the SAW filter and is a terminal electrode 48 is the same as that of the tenth embodiment in FIG.
Same as 2. The difference from the SAW filter of Example 102 is that the side surface is inclined and forms an obtuse angle with the upper surface.

Therefore, the adhesive strength of the side electrode 47 is increased, and the contact area between the Au layer 45 and the side electrode 47 is increased, so that the comb-shaped electrode 43 can be formed reliably. The inclined side surface is realized by forming a V-shaped groove reaching the substrate 41 with a dicing wheel having a V-shaped tip. The prototype SAW filter showed almost the same propagation loss characteristics as the SAW filter of Example 102. Example 5 A SAW filter having the shape shown in FIG. 2 was manufactured by using the c-plane of sapphire (Al ₂ O ₃ ) instead of the glass substrate of Example 2. Au / Cr is used as the metal layer,
ZnO was epitaxially grown as the piezoelectric layer.

FIG. 8 also shows the propagation loss of the SAW filter thus manufactured. The propagation loss is smaller than that of the second embodiment. This is particularly noticeable on the high frequency side, and
It shows that it can be used up to GHz. this is,
This is because a ZnO layer close to a single crystal having almost no crystal grain boundaries can be obtained on sapphire, so that scattering of SAW due to the grain boundaries is suppressed and high-frequency characteristics are improved.

As a substrate, instead of c-plane of sapphire, R
The same effect can be obtained by using a surface. Z as piezoelectric layer
The same effect can be obtained by using AlN instead of nO.

[0047]

As described above, the SAW filter of the present invention has a comb electrode formed by alternately stacking metal layers and piezoelectric layers on a substrate. Therefore, S
As a comb-tooth spacing that determines the frequency limit of the AW filter, for example, a size smaller than the limit of conventional photolithography of 0.01 μm can be realized, and the SAW filter is suitable for high frequencies.

Furthermore, since the SAW has a structure utilizing a longitudinal wave faster than a transverse wave, the SAW can be operated at a higher speed, and a SAW filter suitable for a higher frequency can be obtained. . As a result, 30-
A 120-GHz high-frequency SAW filter can be easily realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a SAW filter according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a SAW filter according to a second embodiment of the present invention.

3 (a) to 3 (g) are cross-sectional views in a process order for explaining a method of manufacturing the SAW filter of FIG. 1;

4 (a) to 4 (f) are cross-sectional views in the order of steps following FIG. 3 (g).

5 (a) to 5 (h) are cross-sectional views in a process order for explaining a method of manufacturing the SAW filter of FIG. 2;

FIG. 6 is a sectional view of a step following FIG. 4 (f);

7A and 7B are cross-sectional views of a step following FIG. 5H.

FIG. 8 is a graph showing propagation loss characteristics of SAW filters according to Embodiments 2 and 5 of the present invention.

FIG. 9 is a perspective view of a SAW filter according to a third embodiment of the present invention.

FIG. 10 is a perspective view of a SAW filter according to Embodiment 4 of the present invention.

FIG. 11 is a perspective view of an example of a conventional SAW filter.

[Explanation of symbols]

1, 11, 21, 31, 41 Substrate 2, 12, 12a-e, 22, 22a-d, 32 Piezoelectric layer or ZnO layer 3, 13, 23, 33, 43 Comb electrode 4, 14, 24, 34 SAW propagation unit 5, 15, 15a-e, 25, 25a-b, 35, 45
Metal layer or Au layer 16, 26a, 26b, 36 Comb electrode portion 27, 37, 47 Side electrode 28, 38, 48 Terminal electrode 29, 39 Protective layer 20a-e, 30a-b Photoresist 50 Groove 100, 101, 102, 103, 104 SAW filter

Claims (10)

[Claims] 1. A comb-teeth electrode part in which a pair of comb teeth in which a metal layer and a piezoelectric layer are alternately laminated on an insulating substrate are intertwined with each other, a surface acoustic wave propagation part formed thereon, and A surface acoustic wave filter having a comb-shaped electrode portion formed thereon as described above. 2. The surface acoustic wave filter according to claim 1, wherein the piezoelectric layer and the surface acoustic wave propagation portion are made of a c-axis oriented polycrystalline film of zinc oxide or aluminum nitride. 3. The surface acoustic wave filter according to claim 2, wherein the metal layer is one of gold, a composite film of gold / titanium, aluminum, and platinum. 4. The surface acoustic wave filter according to claim 1, wherein the piezoelectric layer and the surface acoustic wave propagation portion are made of a c-axis oriented polycrystalline film of lead zirconate titanate, and the metal layer is platinum. . 5. The surface acoustic wave filter according to claim 1, wherein the substrate is made of silicon or glass. 6. The surface acoustic wave filter according to claim 2, wherein a c-plane or an R-plane of sapphire is used as the substrate, and a gold / chromium composite film is used as the metal layer. 7. The surface acoustic wave filter according to claim 1, wherein a terminal electrode connected to the comb electrode is provided on an upper surface of the laminate. 8. The elasticity according to claim 1, wherein the metal layers laminated with the piezoelectric layer interposed therebetween are connected by a metal film formed on a side surface to form a comb-shaped electrode. Surface wave filter. 9. The surface acoustic wave filter according to claim 8, wherein the side surface is inclined at an obtuse angle with respect to the surface of the laminate. 10. A comb-teeth electrode part in which a pair of comb teeth in which a metal layer and a piezoelectric layer are alternately laminated on an insulating substrate are intertwined with each other, a surface acoustic wave propagation part formed thereon. Further, in the method for manufacturing a surface acoustic wave filter having the same comb-shaped electrode portion formed thereon as described above, a photoresist is applied on the deposited first film, and a pattern of the first film is formed. A method of manufacturing a surface acoustic wave filter, comprising: removing the photoresist after depositing two films, and filling a removed portion of the first film with a second film.