Surface acoustic wave (SAW) filter with dielectric material disposed in piezoelectric layer

Abstract

An apparatus for implementing a surface acoustic wave (SAW) filter having a dielectric material (134) disposed in a piezoelectric layer (132) is disclosed. In an example aspect, the apparatus includes a surface acoustic wave filter having a piezoelectric layer (132), an electrode structure (306-1, 306-2), and a dielectric material (134). The piezoelectric layer has at least one channel (134). The dielectric material is disposed in the at least one channel of the piezoelectric layer and at least partially covered by the electrode structure.

Description

Technical Field

[0001] The present disclosure relates generally to wireless transceivers and other components employing filters, and more particularly to surface acoustic wave (SAW) filters having a dielectric material disposed in at least one channel of a piezoelectric layer. Background Art

[0002] Electronic devices use radio frequency (RF) signals to communicate information. These RF signals enable users to talk with friends, download information, share pictures, remotely control home devices, and receive global positioning information. In order to send or receive RF signals within a given frequency band, electronic devices may use filters to pass signals within the band and suppress (e.g., attenuate) interference or noise with frequencies outside the band. However, designing filters that provide filtering for RF applications, including those utilizing frequencies above 2 gigahertz (GHz), can be challenging. Summary of the invention

[0003] A device for implementing a surface acoustic wave (SAW) filter having a dielectric material disposed in a piezoelectric layer is disclosed. Instead of increasing the mass of an electrode structure within a trap region of the surface acoustic wave filter, an example technique uses a piezoelectric layer having at least one channel present within the trap region. The dielectric material is disposed in the channel and enables the surface acoustic wave filter to operate in a piston mode. Compared to other stray mode suppression techniques, the surface acoustic wave filter can attenuate stray modes over a wider frequency range by utilizing a dielectric material at least partially embedded within the piezoelectric layer. Additionally, disposing the dielectric material within the channel of the piezoelectric layer can be easier to manufacture, particularly for high frequency applications, compared to other stray mode suppression techniques.

[0004] In an example aspect, a device for filtering is disclosed. The device includes a surface acoustic wave filter having a piezoelectric layer, an electrode structure, and a dielectric material. The piezoelectric layer has at least one channel. The dielectric material is disposed in the at least one channel of the piezoelectric layer and is at least partially covered by the electrode structure.

[0005] In an example aspect, a device for filtering is disclosed. The device includes a surface acoustic wave filter configured to generate a filtered signal from a radio frequency signal. The surface acoustic wave filter includes a component for converting the radio frequency signal into an acoustic wave and converting the propagated acoustic wave into the filtered signal. The surface acoustic wave filter also includes a component for propagating the acoustic wave across a flat surface to produce the propagated acoustic wave. The surface acoustic wave filter additionally includes a component for operating according to a piston mode. The component for operating is disposed in the component for propagating and is at least partially covered by the component for converting.

[0006] In an example aspect, a method for manufacturing a surface acoustic wave filter is disclosed. The method includes providing a piezoelectric layer. The method also includes etching at least one channel in a surface of the piezoelectric layer. Additionally, the method includes depositing a dielectric material in at least one channel. The method also includes providing an electrode structure at least partially covering the dielectric material.

[0007] In an example aspect, a device is disclosed. The device includes a piezoelectric layer and a dielectric material. The piezoelectric layer is configured to propagate an acoustic wave along a first axis. The piezoelectric layer has at least one recessed region having a longitudinal axis substantially parallel to the first axis. The dielectric material is positioned in the recessed region and has at least one surface exposed. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 An example operating environment for a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0009] Figure 2 An example wireless transceiver including at least one surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0010] Figure 3 An example component of a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0011] Figure 4-1 Example implementations of thin film surface acoustic wave filters having a dielectric material disposed in a piezoelectric layer are illustrated.

[0012] Figure 4-2 Example implementations of high quality temperature compensated surface acoustic wave filters having a dielectric material disposed in a piezoelectric layer are illustrated.

[0013] Figure 5 Example electrode structures for surface acoustic wave filters having a dielectric material disposed in a piezoelectric layer are illustrated.

[0014] Figure 6 A first example implementation of a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0015] Figure 7 A second example implementation of a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0016] Figure 8 A third example implementation of a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0017] Fig. 9A fourth example implementation of a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated.

[0018] Fig.10 Example frequency responses of specific implementations of surface acoustic wave filters including and not including a dielectric material disposed in a piezoelectric layer are illustrated.

[0019] Fig.11 is a flow chart illustrating an example process for fabricating a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer. DETAILED DESCRIPTION

[0020] In order to send or receive radio frequency signals within a given frequency band, electronic devices may use filters to pass signals within the frequency band and suppress (e.g., attenuate) interference or noise with frequencies outside the frequency band. Electroacoustic devices (e.g., "acoustic filters") may be used to filter high-frequency signals (such as those with frequencies greater than 100 megahertz (MHz)) in many applications. Acoustic filters are tuned to pass certain frequencies (e.g., frequencies within their passband) and attenuate other frequencies (e.g., frequencies outside their passband). Using piezoelectric materials as vibrating media, acoustic filters operate by transforming electrical signal waves propagating along electrical conductors into acoustic waves (e.g., acoustic signal waves) formed on piezoelectric materials. The acoustic waves are then converted back into electrical filter signals. Acoustic filters may include electrode structures that transform or convert between electrical waves and acoustic waves.

[0021] Acoustic waves propagate through piezoelectric materials at a speed whose magnitude is significantly less than the magnitude of the propagation speed of electromagnetic waves. Generally speaking, the magnitude of the propagation speed of a wave is proportional to the size of the wavelength of the wave. Therefore, after converting the electrical signal wave into an acoustic signal wave, the wavelength of the acoustic signal wave is significantly smaller than the wavelength of the electrical signal wave. The resulting smaller wavelength of the acoustic signal wave enables the use of smaller filter devices to perform filtering. This permits the use of acoustic filters in space-constrained devices, including portable electronic devices such as cellular phones.

[0022] However, it may be challenging to design an acoustic filter that provides filtering for high frequency applications (including those utilizing frequencies above 2 gigahertz (GHz)) while maintaining or reducing spurious modes (e.g., spurious wave modes) below a certain level within the passband. Spurious modes are undesirable modes that can reduce the performance of the acoustic filter. Some filter designs customize the geometry of the electrode structure of the acoustic filter to attenuate spurious modes. As an example, the fingers within the electrode structure may have a varying width or height across the length of the fingers. Specifically, the fingers may have a wider and / or higher profile (e.g., including hammers and points, respectively) in the trap region of the acoustic filter compared to the active track region of the acoustic filter. In the trap region and the active track region, the projections of adjacent fingers of the acoustic filter overlap. The trap region is adjacent to the active track region and may include the ends of the fingers. Adding hammers and points to the fingers increases the mass of the electrode structure in the trap region relative to the active track region. Customizing the electrode structure in this way can attenuate (e.g., suppress) some types of spurious modes.

[0023] Although this technique enables the suppression of spurious modes, applying this technique to acoustic filters supporting higher frequencies (such as in bands 7, 40, 41, n77 and n79; at 2.4 GHz In some cases, the size of the hammerhead or dot within the trap region may become too small for the manufacturing equipment or may be less practical or cost-prohibitive to produce accurately due to photolithographic constraints.

[0024] To overcome these difficulties, another technique applies dielectric rods across the fingers of the electrode structure to suppress stray modes. In some implementations, the dielectric rods have a thickness of about tens of nanometers, such as about 20 nanometers. However, the dielectric rods may be affected by subsequent manufacturing processes (such as trimming or passivation). Moreover, the dielectric rods may not provide sufficient stray mode suppression within the desired frequency range.

[0025] To address these challenges, example techniques for implementing a surface acoustic wave (SAW) filter having a dielectric material disposed in a piezoelectric layer are described. Instead of or in addition to increasing the mass of an electrode structure within a trap region of a surface acoustic wave filter, the example techniques use a piezoelectric layer having at least one channel present within the trap region. The dielectric material is disposed in the channel and enables the surface acoustic wave filter to operate in a piston mode.

[0026] Certain specific implementations of surface acoustic wave filters having a dielectric material disposed in a piezoelectric layer yield several benefits. These benefits may include operational improvements, manufacturing advantages, or both. One operational benefit is the suppression of spurious modes. Specifically, the dielectric material causes the acoustic waves in the trap region to have a lower velocity than in the active track region. The lower velocity in the trap region suppresses spurious modes, such as transverse modes. By tailoring the geometry of the dielectric material in the trap region, the dielectric material can attenuate spurious modes over a wider frequency range than other technologies.

[0027] From a manufacturing perspective, techniques for disposing a dielectric material within a piezoelectric layer may be easier to implement than techniques for applying a hammer head or point, particularly for high frequency applications. Moreover, in contrast to dielectric rods, the dielectric material is embedded within the piezoelectric layer to form an acoustic wave confinement prior to implementing metallization of the electrode structure. Because the electrode structure at least partially covers the dielectric material, the dielectric material is less exposed to subsequent manufacturing processes, such as trimming and passivation, than a dielectric rod. In this way, a surface acoustic wave filter having a dielectric material disposed in the piezoelectric layer may experience less performance degradation to the piston mode through subsequent processing steps compared to another surface acoustic wave filter having a dielectric rod. Moreover, a surface acoustic wave filter having a dielectric material disposed in the piezoelectric layer may experience less electrical losses than other surface acoustic wave filters having a dielectric rod due to fewer subsequent manufacturing steps after depositing the electrode structure.

[0028] Figure 1 An example environment 100 for operating a surface acoustic wave filter having a dielectric material disposed in a piezoelectric layer is illustrated. In the environment 100, a computing device 102 communicates with a base station 104 via a wireless communication link 106 (wireless link 106). In this example, the computing device 102 is depicted as a smart phone. However, the computing device 102 can be implemented as any suitable computing or electronic device, such as a modem, a cellular base station, a broadband router, an access point, a cellular phone, a gaming device, a navigation device, a media device, a laptop computer, a desktop computer, a tablet computer, a wearable computer, a server, a network attached storage (NAS) device, a smart appliance or other Internet of Things (IoT) device, a medical device, a vehicle-based communication system, a radar, a radio, and the like.

[0029] Base station 104 communicates with computing device 102 via wireless link 106, which may be implemented as any suitable type of wireless link. Although depicted as a cellular network tower, base station 104 may represent or be implemented as another device, such as a satellite, a server device, a terrestrial television broadcast tower, an access point, a peer device, a mesh network node, etc. Thus, computing device 102 may communicate with base station 104 or another device via a wireless connection.

[0030] Wireless link 106 may include a downlink of data or control information communicated from base station 104 to computing device 102, an uplink of other data or control information communicated from computing device 102 to base station 104, or both. Wireless link 106 may be implemented using any suitable communication protocol or standard, such as second generation (2G), third generation (3G), fourth generation (4G), or fifth generation (5G) cellular; IEEE 802.11 (e.g., ); IEEE 802.15 (e.g., ); IEEE 802.16 (e.g., ); etc. In some implementations, the wireless link 106 can provide power wirelessly, and the base station 104 or the computing device 102 can include a power source.

[0031] As shown, computing device 102 includes an application processor 108 and a computer-readable storage medium 110 (CRM 110). Application processor 108 may include any type of processor, such as a multi-core processor, that executes processor executable code stored by CRM 110. CRM 110 may include any suitable type of data storage medium, such as volatile memory (e.g., random access memory (RAM)), non-volatile memory (e.g., flash memory), optical media, magnetic media (e.g., disk), etc. In the context of the present disclosure, CRM 110 is implemented to store instructions 112, data 114, and other information for computing device 102, and therefore does not include transient propagating signals or carrier waves.

[0032] The computing device 102 may also include input / output ports 116 (I / O ports 116) and a display 118. The I / O ports 116 enable data exchange or interaction with other devices, networks, or users. The I / O ports 116 may include serial ports (e.g., universal serial bus (USB) ports), parallel ports, audio ports, infrared (IR) ports, user interface ports such as a touch screen, and the like. The display 118 presents graphics of the computing device 102, such as a user interface associated with an operating system, program, or application. Alternatively or additionally, the display 118 may be implemented as a display port or a virtual interface through which the graphical content of the computing device 102 is presented.

[0033] The wireless transceiver 120 of the computing device 102 provides connectivity to a corresponding network and other electronic devices connected thereto. The wireless transceiver 120 may facilitate communication over any suitable type of wireless network, such as a wireless local area network (WLAN), a peer-to-peer (P2P) network, a mesh network, a cellular network, an ultra-wideband (UWB) network, a wireless wide area network (WWAN), and / or a wireless personal area network (WPAN). In the context of the example environment 100, the wireless transceiver 120 enables the computing device 102 to communicate with the base station 104 and the network connected thereto. However, the wireless transceiver 120 may also enable the computing device 102 to communicate "directly" with other devices or networks.

[0034] The wireless transceiver 120 includes circuits and logic for sending and receiving communication signals via the antenna 122. The components of the wireless transceiver 120 may include amplifiers, switches, mixers, analog-to-digital converters, filters, etc. for conditioning communication signals (e.g., for generating or processing signals). The wireless transceiver 120 may also include logic for performing in-phase / quadrature (I / Q) operations such as synthesis, encoding, modulation, decoding, demodulation, etc. In some cases, the components of the wireless transceiver 120 are implemented as separate transmitter and receiver entities. Additionally or alternatively, the wireless transceiver 120 may be implemented using multiple or different parts to implement corresponding transmission and reception operations (e.g., separate transmission chains and reception chains). In general, the wireless transceiver 120 processes data and / or signals associated with data communicated to the computing device 102 via the antenna 122.

[0035] exist Figure 1 In the example shown, the wireless transceiver 120 includes at least one surface acoustic wave filter 124 (SAW filter 124). In some implementations, the wireless transceiver 120 includes a plurality of surface acoustic wave filters 124, which may be formed by surface acoustic wave resonators arranged in series, in parallel, in a ladder structure, in a lattice structure, or some combination thereof. The surface acoustic wave filter 124 may be a thin film surface acoustic wave filter 126 (TFSAW filter 126) or a high quality temperature compensated surface acoustic wave filter (HQ-TC SAW filter) or another type of surface acoustic wave filter not shown.

[0036] The surface acoustic wave filter 124 includes at least one electrode structure 130, at least one piezoelectric layer 132 (or piezoelectric material), and a dielectric material 134 (e.g., a dielectric or at least one dielectric layer). The dielectric material 134 is at least partially embedded in the piezoelectric layer 132 and at least partially covered by the electrode structure 130. With such a dielectric material 134, the surface acoustic wave filter 124 can operate in a piston mode and attenuate stray modes, such as transverse modes. In general, the piston mode is characterized by a transverse direction (e.g., along the direction with respect to the direction of the wave). Figure 4-1 to Figure 9 The piston mode reduces energy losses by reducing acoustic wave propagation outside the active track region of the SAW filter 124 in the lateral direction and by reducing lateral standing waves within the active track region. Figure 2 The surface acoustic wave filter 124 is further described.

[0037] Figure 2 An example wireless transceiver 120 is illustrated. In the depicted configuration, the wireless transceiver 120 includes a transmitter 202 and a receiver 204, which are coupled to a first antenna 122-1 and a second antenna 122-2, respectively. In other specific implementations, the transmitter 202 and the receiver 204 can be connected to the same antenna through a duplexer (not shown). The transmitter 202 is shown to include at least one digital-to-analog converter 206 (DAC 206), at least one first mixer 208-1, at least one amplifier 210 (e.g., a power amplifier), and at least one first surface acoustic wave filter 124-1. The receiver 204 includes at least one second surface acoustic wave filter 124-2, at least one amplifier 212 (e.g., a low noise amplifier), at least one second mixer 208-2, and at least one analog-to-digital converter 214 (ADC 214). The first mixer 208-1 and the second mixer 208-2 are coupled to a local oscillator 216. Although not explicitly shown, the digital-to-analog converter 206 of the transmitter 202 and the analog-to-digital converter 214 of the receiver 204 may be coupled to ( Figure 1 ) application processor 108 or another processor associated with the wireless transceiver 120 (e.g., a modem).

[0038] In some implementations, wireless transceiver 120 is implemented using multiple circuits (e.g., multiple integrated circuits) such as transceiver circuit 236 and radio frequency front end (RFFE) circuit 238. Thus, the components that form transmitter 202 and receiver 204 are distributed across these circuits. Figure 2As shown, the transceiver circuit 236 includes the digital-to-analog converter 206 of the transmitter 202, the mixer 208-1 of the transmitter 202, the mixer 208-2 of the receiver 204, and the analog-to-digital converter 214 of the receiver 204. In other specific implementations, the digital-to-analog converter 206 and the analog-to-digital converter 214 can be implemented on another separate circuit including the application processor 108 or the modem. The RF front-end circuit 238 includes the amplifier 210 of the transmitter 202, the surface acoustic wave filter 124-1 of the transmitter 202, the surface acoustic wave filter 124-2 of the receiver 204, and the amplifier 212 of the receiver 204.

[0039] During transmission, the transmitter 202 generates a radio frequency transmit signal 218 that is transmitted using the antenna 122-1. To generate the radio frequency transmit signal 218, the digital-to-analog converter 206 provides a pre-up-converted transmit signal 220 to the first mixer 208-1. The pre-up-converted transmit signal 220 may be a baseband signal or an intermediate frequency signal. The first mixer 208-1 uses a local oscillator (LO) signal 222 provided by the local oscillator 216 to up-convert the pre-up-converted transmit signal 220. The first mixer 208-1 generates an up-converted signal, which is referred to as a pre-filter transmit signal 224. The pre-filter transmit signal 224 may be a radio frequency signal and include some noise or unwanted frequencies, such as harmonic frequencies. The amplifier 210 amplifies the pre-filter transmit signal 224 and passes the amplified pre-filter transmit signal 224 to the first surface acoustic wave filter 124-1.

[0040] The first surface acoustic wave filter 124-1 filters the amplified pre-filter transmit signal 224 to generate a filtered transmit signal 226. As part of the filtering process, the first surface acoustic wave filter 124-1 attenuates noise or unwanted frequencies within the pre-filter transmit signal 224. The transmitter 202 provides the filtered transmit signal 226 to the antenna 122-1 for transmission. The transmitted filtered transmit signal 226 is represented by the RF transmit signal 218.

[0041] During reception, the antenna 122-2 receives the RF receive signal 228 and passes the RF receive signal 228 to the receiver 204. The second surface acoustic wave filter 124-2 accepts the received RF receive signal 228, which is represented by the pre-filter receive signal 230. The second surface acoustic wave filter 124-2 filters any noise or unwanted frequencies within the pre-filter receive signal 230 to generate a filtered receive signal 232.

[0042] The amplifier 212 of the receiver 204 amplifies the filtered received signal 232 and passes the amplified filtered received signal 232 to the second mixer 208-2. The second mixer 208-2 downconverts the amplified filtered received signal 232 using the local oscillator signal 222 to generate a downconverted received signal 234. The analog-to-digital converter 214 converts the downconverted received signal 234 into a digital signal that can be processed by the application processor 108 or another processor associated with the wireless transceiver 120 (e.g., a modem).

[0043] Figure 2 One example configuration of the wireless transceiver 120 is illustrated. Other configurations of the wireless transceiver 120 may support multiple frequency bands and share the antenna 122 across multiple transceivers. A person of ordinary skill in the art may appreciate various other configurations that may include the surface acoustic wave filter 124. For example, the surface acoustic wave filter 124 may be integrated into a duplexer or a diplexer of the wireless transceiver 120. Figures 3 to 9 An example implementation of the surface acoustic wave filter 124 - 1 or 124 - 2 is further described.

[0044] Figure 3 An example component of a surface acoustic wave filter 124 is illustrated. In the depicted configuration, the surface acoustic wave filter 124 includes an electrode structure 130, a piezoelectric layer 132, a dielectric material 134, and at least one substrate layer 302. The electrode structure 130 includes a conductive material (such as a metal) and may include one or more layers. The one or more layers may include one or more metal layers and may optionally include one or more adhesion layers. As an example, the metal layer may be composed of aluminum (Al), copper (Cu), silver (Ag), gold (Au), tungsten (W), platinum (Pt), or some combination or doping thereof. The adhesion layer may be composed of chromium (Cr), titanium (Ti), molybdenum (Mo), or some combination thereof.

[0045] The electrode structure 130 may include one or more IDTs 304. The IDTs 304 convert electrical signals into acoustic waves and convert acoustic waves into filtered electrical signals. The IDTs 304 include at least two comb structures 306-1 and 306-2. Each comb structure 306-1 and 306-2 includes a busbar 308 (e.g., a conductive segment or conductive rail) and a plurality of fingers 310 (e.g., electrode fingers). Figure 4-1 and Figure 4-2 An example IDT 304 is further described. Although not explicitly shown, the electrode structure 130 may also include two or more reflectors. In an example implementation, the IDT 304 is disposed between two reflectors that reflect sound waves back toward the IDT 304.

[0046] In an example implementation, the piezoelectric layer 132 may be implemented using a variety of different materials that exhibit piezoelectric properties (e.g., can convert mechanical energy into electrical energy or convert electrical energy into mechanical energy). Example types of materials include lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz, aluminum nitride (AlN), aluminum scandium nitride (AlScN), or some combination thereof. Generally speaking, the material forming the piezoelectric layer 132 has a crystalline structure. This crystalline structure is defined by an ordered arrangement of particles (e.g., atoms, ions, or molecules).

[0047] The piezoelectric layer 132 has at least one channel 312 (e.g., at least one recessed area or at least one groove) on the surface facing the electrode structure 130. The channel 312 may be adjacent to the beginning and / or end of the finger 310 of the electrode structure 130. The term "adjacent" may mean that the channel 312 is closer to the beginning or end of the finger 310 than to the middle or center portion of the finger 310. Explained in another way, the channel 312 is aligned with the beginning and / or end of the finger 310 so that it is disposed within the trap region of the surface acoustic wave filter 124, which will be related to Figure 5 Generally speaking, the channel 312 may pass “underneath” one or more fingers 310 of the electrode structure 130 .

[0048] In some implementations, the channel 312 includes a channel adjacent to a boundary of an active track region of the SAW filter 124, such as with respect to Figure 6 In other embodiments, channel 312 is implemented using two or more channels that are substantially parallel and adjacent to the boundary of the active track area, such as Figure 7 In some further implementations, the channel 312 includes a plurality of segmented channels aligned along axes substantially parallel to the direction of acoustic wave propagation and adjacent to the boundaries of the active track region. The segmented channels may be partially covered by the electrode structure 130, as described with respect to Figure 8 As described, it is completely covered by the electrode structure 130, as described with respect to Fig. 9 In some implementations, the longitudinal axis of the channel 312 is substantially orthogonal to the longitudinal axis of the finger 310. Furthermore, the longitudinal axis of the channel 312 can be substantially parallel to the direction of sound wave propagation, such as with respect to Figure 4-1 and Figure 4-2 as further described.

[0049] The dielectric material 134 may be formed using a variety of different types of dielectric materials, such as tantalum oxide (Ta2O5), silicon oxide (SiO), silicon dioxide (SiO2), silicon nitride (SiN), hafnium oxide (HfO2), aluminum oxide (Al2O3), tungsten trioxide (WO3), niobium pentoxide (Nb2O5), or some combination or doping thereof. In some implementations, the dielectric material 134 is implemented using multiple layers formed using the same material or different materials. The dielectric material 134 may be at least partially buried or embedded within the piezoelectric layer 132. Specifically, the dielectric material 134 is disposed in (or positioned in) one or more channels 312 of the piezoelectric layer 132. Generally, the surface of the dielectric material 134 facing the electrode structure 130 is exposed or not covered by the piezoelectric layer 132. In some implementations, at least a portion of the surface of the dielectric material 134 may be in direct contact with the electrode structure 130. In an alternative implementation, a dielectric layer (not shown) is present between the electrode structure 130 and the dielectric material 134. In an example implementation, the dielectric layer has a thickness of about 10 nanometers or less (e.g., 10 nanometers, 8 nanometers, 5 nanometers, or 2 nanometers). Generally, the dielectric material 134 is at least partially covered by the electrode structure 130.

[0050] The substrate layer 302 includes one or more sub-layers that may support passivation, temperature compensation, power handling, mode suppression, etc. As an example, the substrate layer 302 may include at least one compensation layer 314, at least one charge trapping layer 316, at least one support layer 318, or some combination thereof. These sub-layers may be considered part of the substrate layer 302 or their own separate layers.

[0051] The compensation layer 314 can provide temperature compensation so that the surface acoustic wave filter 124 can achieve a target frequency temperature coefficient based on the thickness of the piezoelectric layer 132. In some implementations, the thickness of the compensation layer 314 can be tailored to provide mode suppression (e.g., suppress stray plate modes). In an example implementation, the compensation layer 314 can be implemented using at least one silicon dioxide (SiO2) layer, at least one doped silicon dioxide layer, at least one silicon nitride layer, at least one silicon oxynitride layer, or some combination thereof. In some applications, the substrate layer 302 may not include, for example, the compensation layer 314 to reduce the cost of the surface acoustic wave filter 124.

[0052] The charge trapping layer 316 can trap induced charges at the interface between the compensation layer and the support layer, for example, to suppress nonlinear substrate effects. The charge trapping layer 316 can include at least one polycrystalline silicon (poly-Si) layer (e.g., a polycrystalline silicon layer or a multicrystalline silicon layer), at least one amorphous silicon layer, at least one silicon nitride (SiN) layer, at least one silicon oxynitride (SiON) layer, at least one aluminum nitride (AlN) layer, diamond-like carbon (DLC), diamond, or some combination thereof.

[0053] The support layer 318 can enable acoustic waves to form across the surface of the piezoelectric layer 132 and reduce the amount of energy that leaks into the substrate layer 302. In some implementations, the support layer 318 can also serve as the compensation layer 314. Generally speaking, the support layer 318 is composed of a material that is non-conductive and provides isolation. For example, the support layer 318 can be formed using a silicon (Si) material (e.g., a doped high-resistance silicon material), a sapphire material (e.g., aluminum oxide (Al2O3)), a silicon carbide (SiC) material, a fused silica material, quartz, glass, diamond, or some combination thereof. In some implementations, the support layer 318 has a relatively similar thermal expansion coefficient (TEC) as the piezoelectric layer 132. The support layer 318 can also have a specific crystal orientation to support the suppression or attenuation of stray modes.

[0054] In some aspects, the surface acoustic wave filter 124 can be considered a resonator. Sometimes, the surface acoustic wave filter 124 can be connected to other resonators associated with a layer stack different from the surface acoustic wave filter 124. In other aspects, the surface acoustic wave filter 124 can be implemented as multiple interconnected resonators using the same layer (e.g., the piezoelectric layer 132 and / or the substrate layer 302). Figure 4-1 and Figure 4-2 The electrode structure 130, the piezoelectric layer 132, and the dielectric material 134 are further described.

[0055] Figure 4-1 An example implementation of a thin film surface acoustic wave filter 126 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Figure 4-1 A three-dimensional perspective view 400-1 of the thin film surface acoustic wave filter 126 is shown at the top of Figure 4-1 The bottom portion of FIG. 4 shows a two-dimensional cross-sectional view 400 - 2 of the thin film surface acoustic wave filter 126 .

[0056] The thin film surface acoustic wave filter 126 includes at least one electrode structure 130, at least one piezoelectric layer 132, and at least one substrate layer 302. The electrode structure 130 may include one or more interdigital transducers 304. In the depicted configuration shown in the two-dimensional cross-sectional view 400-2, the piezoelectric layer 132 is disposed between the electrode structure 130 and the substrate layer 302.

[0057] In the three-dimensional perspective view 400-1, the interdigital transducer 304 is shown as having two comb structures 306-1 and 306-2, in which fingers 310 extend from two busbars 308 toward each other. The fingers 310 are arranged in an interlocking manner between the two busbars 308 of the interdigital transducer 304 (e.g., arranged in an interdigitated manner). In other words, the fingers 310 connected to the first busbar 308 extend toward the second busbar 308 but are not connected to the second busbar 308. Therefore, there is a barrier region 402 (e.g., a lateral gap region) between the ends of these fingers and the second busbar 308. Similarly, the fingers 310 connected to the second busbar 308 extend toward the first busbar 308 but are not connected to the first busbar 308. Therefore, there is a barrier region 402 between the ends of these fingers 310 and the first busbar 308, as shown in FIG. Figure 5 as further described.

[0058] In a direction along the busbar 308, there is an overlap region that includes a central region 404 where a portion of one finger 310 overlaps a portion of an adjacent finger 310. This central region 404 including the overlap may be referred to as an orifice, track, or active region where an electric field is generated between the fingers 310 to cause an acoustic wave 406 to form in at least this region of the piezoelectric layer 132.

[0059] The physical periodicity of the fingers 310 is referred to as the spacing 408 of the interdigital transducer 304. The spacing 408 can be indicated in various ways. For example, in some aspects, the spacing 408 can correspond to the magnitude of the distance between adjacent fingers 310 of the interdigital transducer 304 in the central area 404. For example, the distance can be defined as the distance between the center points of each finger in the fingers 310. When the fingers 310 have a uniform width, the distance can usually be measured between the right (or left) edge of one finger 310 and the right (or left) edge of the adjacent finger 310. In some aspects, the average value of the distance between adjacent fingers 310 of the interdigital transducer 304 can be used for the spacing 408. The frequency at which the piezoelectric layer 132 vibrates is the main resonant frequency of the electrode structure 130. This frequency is determined at least in part by the spacing 408 of the interdigital transducer 304 and other properties of the thin film surface acoustic wave filter 126.

[0060] In the three-dimensional perspective view 400-1, the thin film surface acoustic wave filter 126 is defined by a first (X) axis 410, a second (Y) axis 412, and a third (Z) axis 414. The first axis 410 and the second axis 412 are parallel to the planar surface of the piezoelectric layer 132, and the second axis 412 is perpendicular to the first axis 410. The third axis 414 is perpendicular to the planar surface of the piezoelectric layer 132 (e.g., perpendicular or orthogonal). The busbars 308 of the interdigital transducer 304 are oriented parallel to the first axis 410. The fingers 310 of the interdigital transducer 304 are oriented parallel to the second axis 412. Moreover, the orientation of the piezoelectric layer 132 causes the acoustic wave 406 to be formed primarily in the direction of the first axis 410. Therefore, the acoustic wave 406 is formed in a direction that is substantially perpendicular or orthogonal to the direction of the fingers 310 of the interdigital transducer 304.

[0061] At least one channel 312 is formed or etched in the surface of the piezoelectric layer 132 that faces the electrode structure 130. Figure 4-1 In the example implementation shown, piezoelectric layer 132 has two channels 312 that are located adjacent to the outer boundaries or outer edges of central region 404. Dielectric material 134 is disposed in both channels 312. The surface of dielectric material 134 that faces electrode structure 130 can be substantially flush with the surface of piezoelectric layer 132 that also faces electrode structure 130. In some cases, the surface of dielectric material 134 that faces away from electrode structure 130 is adhered to the surface of piezoelectric layer 132 that faces electrode structure 130. Figure 4-2 Another example type of surface acoustic wave filter 124 is further described.

[0062] Figure 4-2 An example implementation of a high quality temperature compensated surface acoustic wave filter 128 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Figure 4-2 A three-dimensional perspective view 400-3 of the high quality temperature compensated surface acoustic wave filter 128 is shown at the top of Figure 4-2 The bottom portion of FIG. 4 shows a two-dimensional cross-sectional view 400 - 4 of the high-quality temperature-compensated surface acoustic wave filter 128 .

[0063] The high-quality temperature-compensated surface acoustic wave filter 128 includes at least one electrode structure 130, at least one piezoelectric layer 132, and at least one compensation layer 314. The compensation layer 314 can provide temperature compensation to enable the high-quality temperature-compensated surface acoustic wave filter 128 to achieve a target frequency temperature coefficient. In an example implementation, the compensation layer 314 can be implemented using at least one silicon dioxide layer.

[0064] In the depicted configuration shown in the two-dimensional cross-sectional view 400-4, the electrode structure 130 is disposed between the piezoelectric layer 132 and the compensation layer 314. The piezoelectric layer 132 may form a substrate for the high quality temperature compensated surface acoustic wave filter 128.

[0065] The electrode structure 130 of the high quality temperature compensated surface acoustic wave filter 128 may be similar to that described above with respect to Figure 4-1 Similarly, the piezoelectric layer 132 of the high quality temperature compensated surface acoustic wave filter 128 can be similar to the electrode structure 130 described above with respect to the thin film surface acoustic wave filter 126. Figure 4-1 The piezoelectric layer 132 of the thin film surface acoustic wave filter 126 is described. However, with Figure 4-1 The piezoelectric layer 132 of the high-quality temperature-compensated surface acoustic wave filter 128 can be thicker than the piezoelectric layer 132 of the thin-film surface acoustic wave filter 126. Figure 4-1 Thin film surface acoustic wave filter 126, Figure 4-2 The high-quality temperature-compensated surface acoustic wave filter 128 may also include a barrier region 402 and a central region 404 .

[0066] The high quality temperature compensated surface acoustic wave filter 128 may have at least one channel 312 formed or etched in the surface of the piezoelectric layer 132 facing the electrode structure 130. Figure 4-2 In the example implementation shown, the piezoelectric layer 132 has two channels that are located adjacent to the outer boundary or outer edge of the central region 404. The dielectric material 134 is disposed in the two channels 312. The surface of the dielectric material 134 that faces the electrode structure 130 can be substantially flush with the surface of the piezoelectric layer 132 that also faces the electrode structure 130. In some cases, the surface of the dielectric material 134 that faces away from the electrode structure 130 is adhered to the surface of the piezoelectric layer 132 that faces the electrode structure 130.

[0067] For both the thin film surface acoustic wave filter 126 and the high quality temperature compensated surface acoustic wave filter 128, various properties associated with the dielectric material 134 (and the channel 312) can be tailored to achieve a target level of spurious mode suppression for a particular frequency range. For example, the density and / or stiffness of the dielectric material 134, the location of the dielectric material 134 (and the channel 312 or multiple channels 312) within the central region 404, the length of the dielectric material 134 (and the channel 312) along the first (X) axis 410, the width of the dielectric material 134 (and the channel 312) along the second (Y) axis 412, and / or the thickness of the dielectric material 134 (e.g., the depth of the channel 312) along the third (Z) axis 414 can be designed to attenuate the transverse modes across the frequency range by a specific amount. Specifically, the width of the dielectric material 134 can be based at least in part on the frequency range. Additionally, these properties can be tailored to provide a geometry that produces a velocity distribution according to a piston mode. For example, the thickness and / or width of the dielectric material 134 may be designed to achieve a particular velocity within the trap region 506 .

[0068] The thickness of the dielectric material 134 along the third (Z) axis 414 may be between approximately 5% and 100% of twice the length of the spacing 408. For the example thin film surface acoustic wave filter 126 or the example high quality temperature compensated surface acoustic wave filter 128, the thickness of the dielectric material 134 may be approximately 5%, 10%, 25%, 50%, 75%, 80%, or 100% of twice the length of the spacing 408. In the event that the thickness of the piezoelectric layer 132 is less than twice the spacing 408, the thickness of the dielectric material 134 may be less than or equal to the thickness of the piezoelectric layer 132. In general, the term "approximately" may mean that any thickness may be within + / -10% or less of a specified value (e.g., within + / -5%, + / -3%, or + / -2% of a specified value). In general, increasing the thickness of the dielectric material 134 reduces the velocity of the acoustic waves 406 within the trap region 506. With respect to Figures 6 to 9 Various implementations of the channel 312 and the dielectric material 134 are further described. Figure 4-1 Thin film surface acoustic wave filter 126 and Figure 4-2 The high quality temperature compensated surface acoustic wave filter 128 may have similar operations generally described below with respect to the surface acoustic wave filter 124 .

[0069] During operation, the surface acoustic wave filter 124 (eg, Figure 4-1 Thin film surface acoustic wave filter 126 or Figure 4-2 The high quality temperature compensated surface acoustic wave filter 128) receives RF signals such as Figure 2, or the pre-filtered transmit signal 224 or the pre-filtered receive signal 230 shown in . The electrode structure 130 excites the acoustic wave 406 on the piezoelectric layer 132 using the inverse piezoelectric effect. For example, the interdigital transducers 304 in the electrode structure 130 generate an alternating electric field based on the received radio frequency signal. The piezoelectric layer 132 enables the acoustic wave 406 to be formed in response to the alternating electric field generated by the interdigital transducers 304. In other words, the piezoelectric layer 132 at least partially enables the acoustic wave 406 to be formed in response to the electrical stimulation performed by one or more interdigital transducers 304.

[0070] Acoustic wave 406 propagates across piezoelectric layer 132 and interacts with IDT 304 or another IDT within electrode structure 130 ( Figure 4-1 or Figure 4-2 The propagating acoustic wave 406 may be a standing wave. In some implementations, two reflectors within the electrode structure 130 cause the acoustic wave 406 to be formed as a standing wave across a portion of the piezoelectric layer 132. In other implementations, the acoustic wave 406 propagates from the interdigital transducer 304 across the piezoelectric layer 132 to another interdigital transducer (not shown).

[0071] Using the piezoelectric effect, the electrode structure 130 generates a filtered RF signal based on the propagating surface acoustic wave 406. Specifically, due to the mechanical stress generated by the propagation of the acoustic wave 406, the piezoelectric layer 132 generates an alternating electric field. The alternating electric field induces an alternating current in another interdigital transducer or the interdigital transducer 304. The alternating current forms a filtered RF signal provided at the output of the surface acoustic wave filter 124. The filtered RF signal may include Figure 2 The filtered transmit signal 226 or the filtered receive signal 232 .

[0072] It should be understood that although Figure 4-1 and Figure 4-2 A certain number of fingers are illustrated in the example, but the actual number of fingers and the length and width of the fingers and busbars may be different in actual implementations. Such parameters depend on the specific application and the desired filter characteristics. In addition, the thin film surface acoustic wave filter 126 or the high quality temperature compensated surface acoustic wave filter 128 may include a plurality of interconnected electrode structures, each of which includes a plurality of interdigital transducers 304 to achieve a desired passband (e.g., a plurality of interconnected resonators or interdigital transducers 304 connected in series or in parallel to form a desired filter transfer function).

[0073] Although not explicitly shown, the electrode structure 130 may also include two or more reflectors. In an example implementation, the interdigital transducer 304 is arranged between two reflectors (not shown), which reflect the sound waves back to the interdigital transducer 304. Each reflector in the electrode structure 130 may have a grating structure with two busbars and conductive fingers connected to the two busbars. In some implementations, the spacing of the reflectors may be similar or the same as the spacing 408 of the interdigital transducer 304 to reflect the sound waves 406 within the resonant frequency range.

[0074] Figure 5 An example electrode structure 130 of a surface acoustic wave filter 124 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Figure 5 The surface acoustic wave filter 124 may be Figure 4-1 Thin film surface acoustic wave filter 126 or Figure 4-2 High quality temperature compensated surface acoustic wave filter 128.

[0075] As shown in the two-dimensional top-down view 500 of the surface acoustic wave filter 124, the electrode structure 130 of the surface acoustic wave filter 124 includes a first busbar 308-1, a second busbar 308-2, and fingers 310-1, 310-2, 310-3, and 310-4. The first busbar 308-1 and the fingers 310-1 and 310-3 form at least a portion of the first comb structure 306-1. The fingers 310-1 and 310-3 are connected to the first busbar 308-1 and extend toward the second busbar 308-2 along the second (Y) axis 412 without being connected to the second busbar 308-2. The second busbar 308-2 and the fingers 310-2 and 310-4 form at least a portion of the second comb structure 306-2. The fingers 310 - 2 and 310 - 4 are connected to the second bus bar 308 - 2 and extend along the second (Y) axis 412 toward the first bus bar 308 - 1 without being connected to the first bus bar 308 - 1 .

[0076] The surface acoustic wave filter 124 includes a plurality of different regions along the second (Y) axis 412. These regions are defined based at least in part on the physical layout of the electrode structure 130. These regions include a busbar region 502, a barrier region 402, and a central region 404. The busbar region 502 includes busbars 308-1 and 308-2 and extends along a portion of the second (Y) axis 412 corresponding to the width of the busbars 308-1 and 308-2. In this case, two busbar regions 502 are shown as being associated with the two busbars 308-1 and 308-2, respectively.

[0077] The barrier region 402 exists between the central region 404 and the busbar region 502. Specifically, the barrier region 402 includes a portion of the second (Y) axis 412 that extends between one busbar 308 and the ends of the fingers 310 associated with another busbar 308 (e.g., an opposing busbar). For example, a first barrier region 402 exists between a first busbar 308-1 and the ends of the fingers 310-2 and 310-4 associated with the second busbar 308-2. A second barrier region 402 exists between the second busbar 308-2 and the ends of the fingers 310-1 and 310-3 associated with the first busbar 308-1.

[0078] The central region 404 is defined by the overlap of the fingers 310-1 to 310-4 across the first (X) axis 410. As depicted in the top-down view 500, the central region 404 includes at least one active track region 504 and at least one trap region 506. The trap region 506 exists between the barrier region 402 and the active track region 504. In this way, the trap region 506 exists at the outer boundary or outer edge of the central region 404. The channel 312 and the dielectric material 134 are located within the trap region 506. In this way, the fingers 310-1 to 310-4 of the electrode structure 130 at least partially cover the dielectric material 134 and the channel 312. Generally speaking, the main mode or fundamental mode of the surface acoustic wave filter 124 is designed to propagate within the active track region 504. The active track region 504 may also be referred to as a central excitation region.

[0079] In the case where the dielectric material 132 is disposed in the piezoelectric layer 132, the structural characteristics of the piezoelectric layer 132 in the trap region 506 may be different from other regions including the active track region 504. This change makes ( Figure 4-1 or Figure 4-2 The acoustic wave 406 has a lower velocity (e.g., lower transverse velocity) in the trap region 506. By providing the dielectric material 132 within the piezoelectric layer 132, the velocity profile of the surface acoustic wave filter 124 can be designed to reduce (suppress) stray transverse modes and promote the excitation of the main wave mode or fundamental wave mode.

[0080] The velocity profile indicates the velocity (e.g., wave speed) of each region of the surface acoustic wave filter 124. In an example implementation, the velocity of the acoustic wave 406 is higher in the busbar region 502 and the barrier region 402 compared to the center region 404. Generally speaking, the acoustic wave 406 can easily propagate in regions with lower velocities, such as in the center region 404. The relatively high velocities in the barrier region 402 and the busbar region 502 effectively form a barrier that isolates the center region 404 and reduces leakage (e.g., loss) within the surface acoustic wave filter 124.

[0081] In the central region 404, the velocity in the trap region 506 is lower than the active track region 504. The lower velocity in the trap region 506 can shape the lateral profile (e.g., amplitude) of the fundamental mode. As an example, the velocity difference between the active track region 504 and the trap region 506 can be on the order of tens or hundreds of meters per second (m / s).

[0082] The mode distribution of the surface acoustic wave filter indicates the amplitude of the fundamental mode across different regions. In this example implementation, the mode distribution has a rectangular or pulse shape that corresponds to a piston mode in which stray transverse modes are substantially suppressed (e.g., attenuated). The piston mode is characterized by an amplitude that is substantially flat (e.g., the same) on the active track region 504 and higher within the active track region 504 compared to the busbar region 502 and the barrier region 402. In order to achieve the piston mode and suppress the stray transverse mode, the provision of the dielectric material 134 in the piezoelectric layer 132 increases the mass load applied to the piezoelectric layer 132 within the trap region 506.

[0083] In some implementations, the width of the trap region 506 along the second (Y) axis 412 (e.g., the lateral dimension or transverse size of the trap region 506) can be between about 10% and 300% of the wavelength of the acoustic wave 406 along the first (X) axis 410. For example, the width of the trap region 506 can be between about 25% and 100% of the wavelength of the acoustic wave 406. The width of the trap region 506 along the second (Y) axis 412 can also be relative to the pitch 408 ( Figure 4-1 or Figure 4-2 In an example implementation, the width of the trap region 506 may be the width of the electrode structure 130 at a pitch 408 ( Figure 4-1 or Figure 4-2 408). For example, the width of the trap region 506 can be about 30%, 50%, 100%, or 200% of the pitch 408. As another example, the width of the trap region 506 can be between about 30% and 70% of the pitch 408. In general, the term "about" can mean that any width can be within + / - 10% or less of a specified value (e.g., within + / - 5%, + / - 3%, or + / - 2% of a specified value).

[0084] For clarity, in the top-down view 500, the various regions of the surface acoustic wave filter 124 are not necessarily drawn to scale. In addition, each region may have some variability from the illustrated proportions or widths, including variability caused by the constraints of a given manufacturing technology. For example, the trap region 506 may extend beyond the end of the finger on which the trap region 506 is disposed. It will be appreciated by those of ordinary skill in the art that these dimensions may vary for other example implementations of the surface acoustic wave filter 124.

[0085] In some aspects, the surface acoustic wave filter 124 is implemented using an additional piston mode technique that customizes the geometry of the electrode structure 130. As an example, the fingers 310 within the electrode structure 130 can have a varying width or height across the length of the fingers 310. Specifically, the fingers 310 can have a wider and / or taller profile (e.g., including a hammerhead or a point, respectively) within the trap region 506 relative to the active track region 504. The wider and / or taller profile can be achieved by applying a conductive material (such as a metal) and / or a dielectric material. Such additional material increases the mass of the fingers 310 within the trap region 506 relative to the active track region 504.

[0086] about Figures 6 to 9 Various embodiments of the dielectric material 134 in the further description of the portion 508 of the electrode structure 130. Figure 5 As shown, portion 508 comprises the “lower” portion of the surface acoustic wave filter 124 (as depicted on the drawing). Specifically, portion 508 includes the portion of the trap region 506, the barrier region 402, and the busbar region 502 that is “below” the active track region 504 (as depicted on the drawing). Although portion 508 is Figures 6 to 9 508, but the "upper" portion of the SAW filter 124 (e.g., the trap region 506, the barrier region 402, and a portion of the busbar region 502 "above" the active track region 504) may have a similar configuration as portion 508. Figures 6 to 9 Example configurations of the channel 312 and the dielectric material 134 are further described.

[0087] Figure 6 A first example implementation of a surface acoustic wave filter 124 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Figure 6 The top of the figure shows a three-dimensional perspective view 600-1 of the portion 508 of the surface acoustic wave filter 124. Figure 6 A two-dimensional cross-sectional view 600-2 of the surface acoustic wave filter 124 is shown in the middle, and Figure 6 The bottom of FIG. 6 shows a two-dimensional top-down view 600 - 3 of the surface acoustic wave filter 124 .

[0088] In the portion 508 illustrated in the three-dimensional perspective view 600-1, the piezoelectric layer 132 has a portion 508 positioned within the trap region 506 (e.g., Figure 5 The piezoelectric layer 132 includes a channel 312 (in one of the trap regions 506) of the electrode structure 130. Specifically, the channel 312 is positioned adjacent to the end of the finger 310-3 and the beginning of the finger 310-2. The channel 312 is filled with the dielectric material 134. As shown in the cross-sectional view 600-2 and the top-down view 600-3, the piezoelectric layer 132 may also include another channel 312 in another trap region 506. Each channel 312 has a longitudinal axis that is substantially parallel to the first (X) axis (e.g., the direction of acoustic wave propagation) and substantially perpendicular to the longitudinal axis of the finger 310. As shown in the top-down view 600-3, the fingers 310 of the electrode structure 130 partially cover the dielectric material 134. Therefore, some of the dielectric material 134 is exposed.

[0089] Figure 6 The specific implementations shown in can achieve a target amount of spurious mode suppression for some frequency ranges (such as a low-band frequency range, a mid-band frequency range, or a high-band frequency range). The low-band frequency range may include frequencies below one gigahertz (e.g., Long Term Evolution (LTE) bands 28 or 71). The mid-band and high-band frequency ranges may include frequencies between one gigahertz and three gigahertz (e.g., LTE band 41). As described with respect to Figure 7 As further described, multiple channels 312 in the piezoelectric layer 312 within the trap region 506 can also be implemented to achieve target levels of spurious mode suppression for higher frequency bands, for example, frequencies between three gigahertz and six gigahertz (e.g., fifth generation new radio (5G NR) bands n77 and n79).

[0090] Figure 7 A second example implementation of a surface acoustic wave filter 124 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Figure 7 The top of the figure shows a three-dimensional perspective view 700-1 of the portion 508 of the surface acoustic wave filter 124. Figure 7 A two-dimensional cross-sectional view 700-2 of the surface acoustic wave filter 124 is shown in the middle, and Figure 7 The bottom of FIG. 7 shows a two-dimensional top-down view 700 - 3 of the surface acoustic wave filter 124 .

[0091] In the portion 508 illustrated in the three-dimensional perspective view 700-1, the piezoelectric layer 132 has a portion 508 positioned within the trap region 506 (e.g., positioned within the Figure 5The two channels 312-1 and 312-2 are located in one of the trap regions 506 of the active track region 504 or adjacent to the same boundary of the active track region 504. The two channels 312-1 and 312-2 may be substantially parallel to each other. The channels 312-1 and 312-2 are filled with the dielectric material 134.

[0092] As shown in the cross-sectional view 700-2 and the top-down view 700-3, the piezoelectric layer 132 may also include another set of parallel channels 312 within another trap region 506. Each channel 312 has a longitudinal axis that is substantially parallel to the first (X) axis (e.g., the direction of acoustic wave propagation) and substantially perpendicular to the longitudinal axis of the finger 310. As shown in the top-down view 700-3, the finger 310 of the electrode structure 130 partially covers the dielectric material 134 disposed in each channel 312. Some of the dielectric material 134 is exposed.

[0093] In general, the piezoelectric layer 132 can be implemented with any number of channels 312 (e.g., one, two, three, or four channels 312) within each trap region 506. Each channel 312 provides another degree of freedom to achieve a desired level of spurious mode suppression performance. With this design, the surface acoustic wave filter 124 can achieve a desired level of spurious mode suppression performance for challenging frequency bands including ultra-high frequency bands.

[0094] exist Figure 6 and Figure 7 , the channel 312 is implemented as a continuous channel across the length of the track of the surface acoustic wave filter 124 (e.g., between the outer fingers 310 of the electrode structure 130 along the first (X) axis 410). In an alternative implementation, instead, the channel 312 is implemented using a plurality of segmented channels approximately parallel to the first (X) axis 410, as shown in FIG. Figure 8 and Fig. 9 as further described.

[0095] Figure 8 A third example implementation of a surface acoustic wave filter 124 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Figure 8 The top of the figure shows a three-dimensional perspective view 800-1 of the portion 508 of the surface acoustic wave filter 124. Figure 8 A two-dimensional cross-sectional view 800-2 of the surface acoustic wave filter 124 is shown in the middle, and Figure 8 The bottom of FIG. 8 shows a two-dimensional top-down view 800 - 3 of the surface acoustic wave filter 124 .

[0096] In the portion 508 shown in the three-dimensional perspective view 800-1, the piezoelectric layer 132 has a portion 508 positioned within the trap region 506 (e.g., positioned within the first (X) axis 410). Figure 5 The piezoelectric layer 132 may include a plurality of segmented channels 802 (in one of the trap regions 506 of the electrode structure 130 or positioned near the same boundary of the active track region 504). For example, the piezoelectric layer 132 includes a first segmented channel 802-1, which is positioned "under" the finger 310-3, and a second segmented channel 802-2, which is positioned "under" the finger 310-2. In some cases, the segmented channels 802 are positioned adjacent to the ends of the fingers 310. Optionally, additional segmented channels 802 may be placed adjacent to the beginning of the fingers 310. Generally speaking, each segmented channel 802 may be at least partially covered by a corresponding finger 310 of the electrode structure 130. Adjacent segmented channels 802 are physically separated from each other along the first (X) axis 410. The longitudinal axis of the segmented channel 802 may be substantially parallel to the first (X) axis (e.g., the direction of acoustic wave propagation) and substantially perpendicular to the longitudinal axis of the finger 310.

[0097] As shown in the top-down view 800-3, the piezoelectric layer 132 may also include other segmented channels 802 within another trap region 506. The fingers 310 of the electrode structure 130 partially cover the dielectric material 134. Therefore, some of the dielectric material 134 is exposed. In other words, the length of the segmented channel 802 along the first (X) axis 410 is greater than the width of the fingers 310 along the first (X) axis 410. In other specific implementations, the fingers 310 of the electrode structure 130 completely cover the dielectric material 134, such as with respect to FIG. Fig. 9 as further described.

[0098] Fig. 9 A fourth example implementation of a surface acoustic wave filter 124 having a dielectric material 134 disposed in a piezoelectric layer 132 is illustrated. Fig. 9 The top of the figure shows a three-dimensional perspective view 900-1 of the portion 508 of the surface acoustic wave filter 124. Fig. 9 A two-dimensional cross-sectional view 900-2 of the surface acoustic wave filter 124 is shown in the middle, and Fig. 9 The bottom of FIG. 1 shows a two-dimensional top-down view 900 - 3 of the surface acoustic wave filter 124 .

[0099] In the portion 508 shown in the three-dimensional perspective view 900-1, the piezoelectric layer 132 has a portion 508 positioned within the trap region 506 (e.g., positioned within the first (X) axis 410). Figure 5The piezoelectric layer 132 may include a plurality of segmented channels 802 (in one of the trap regions 506 of the piezoelectric layer 132 or positioned near the same boundary of the active track region 504). For example, the piezoelectric layer 132 includes a first segmented channel 802-1, which is positioned "under" the finger 310-3, and a second segmented channel 802-2, which is positioned "under" the finger 310-2. In some cases, the segmented channels 802 are positioned adjacent to the ends of the fingers 310. Optionally, additional segmented channels 802 may be placed adjacent to the beginning of the fingers 310. Adjacent segmented channels 802 are physically separated from each other along the first (X) axis 410. The longitudinal axis of the segmented channel 802 may be substantially parallel to the first (X) axis (e.g., the direction of acoustic wave propagation) and substantially perpendicular to the longitudinal axis of the finger 310.

[0100] As shown in the three-dimensional perspective view 900-1 and the top-down view 900-3, the fingers 310 of the electrode structure 130 completely cover the dielectric material 134. Therefore, the dielectric material 134 is not exposed. In other words, the length of the segmented channel 802 along the first (X) axis 410 is less than the width of the fingers 310 along the first (X) axis 410.

[0101] One of ordinary skill in the art will appreciate that the dielectric material 134 may be partially embedded in various other configurations of the piezoelectric layer 132. Some specific implementations of the piezoelectric layer 132 may have Figures 6 to 9 For example, the surface acoustic wave filter 124 may include a Figure 8 or Fig. 9 4 and the trap region 506 of the first group of segmented channels 802 and the second group of segmented channels 802 substantially parallel to the first group of segmented channels along the first (X) axis 410 and offset from the first group of segmented channels along the second (Y) axis 412. Explained in another way, the first group of segmented channels 802 and the second group of segmented channels 802 can be positioned adjacent to the same boundary of the active track region 504. As another example, the surface acoustic wave filter 124 can include more than two parallel channels 312 within the trap region 506 (e.g., positioned at Figure 5 The channels 312 may be located within one of the trap regions 506 or positioned adjacent to the same boundary of the active track region 504 , such as three or four channels 312 .

[0102] Although Figure 8 and Fig. 9The segmented channels 802 are shown as being aligned along the same axis that is substantially parallel to the first (X) axis 410, but other implementations of the segmented channels 802 may apply an offset to different groups of segmented channels 802 along the second (Y) axis 412. For example, a first group of segmented channels 802 may be aligned along a first axis that is substantially parallel to the first (X) axis 410 and intersects the second (Y) axis 412 at a first point. A second group of segmented channels 802 may be aligned along a second axis that is substantially parallel to the first (X) axis 410 and intersects the second (Y) axis 412 at a second point different from the first point.

[0103] although Figures 6 to 9 The surface acoustic wave filter 124 is illustrated as a thin film surface acoustic wave filter 126 having a substrate layer 302, but other specific implementations of the surface acoustic wave filter 124 are also possible. For example, Figures 6 to 9 The surface acoustic wave filter 124 may be implemented as a high-quality temperature-compensated surface acoustic wave filter 128 having a piezoelectric layer 132 used as a substrate layer 302 .

[0104] Fig.10 Example frequency responses of specific implementations of surface acoustic wave filters 124 are illustrated, including and excluding dielectric material 134 disposed in piezoelectric layer 132. Graph 1000 depicts frequency response 1002 of another surface acoustic wave filter that does not include dielectric material 134 disposed in piezoelectric layer 132. Instead of dielectric material 134 disposed in piezoelectric layer 132, the other surface acoustic wave filter includes dielectric rods disposed across the fingers of the electrode structure. The dielectric rods enable the other surface acoustic wave filter to operate in piston mode.

[0105] Graph 1000 also depicts a frequency response 1004 of a surface acoustic wave filter 124 that includes a dielectric material 134 disposed in piezoelectric layer 132. Due to the presence of dielectric material 134, the frequency response 1004 of the surface acoustic wave filter 124 can attenuate spurious modes by a greater amount than other surface acoustic wave filters, as shown at 1006. In some cases, this attenuation can be on the order of several decibels (dB) or more (e.g., about 2 dB, 3 dB, 5 dB, 8 dB, or 10 dB). Generally speaking, the term "about" can mean that the attenuation can be within + / - 10% or less of a specified value (e.g., within + / - 5%, + / - 3%, or + / - 2% of a specified value).

[0106] Fig.111 is a flow chart illustrating an example process 1100 for fabricating a surface acoustic wave filter 124 having a dielectric material disposed in a piezoelectric layer. The process 1100 is described in terms of a set of blocks 1102 to 1108 that specify operations that may be performed. However, the operations are not necessarily limited to Fig.11 1100 or described herein, as these operations may be performed in an alternative order or in a fully or partially overlapping manner. Moreover, more, fewer, and / or different operations may be implemented to perform process 1100 or an alternative process. The operations represented by the illustrated blocks of process 1100 may be performed to produce (e.g., Figures 1 to 3 More specifically, the operations of process 1100 may be performed, at least in part, to provide a surface acoustic wave filter 124. Figures 6 to 9 A dielectric material 134 is provided in the piezoelectric layer 132 of the surface acoustic wave filter 124.

[0107] At 1102, a piezoelectric layer is provided. For example, the fabrication process provides a piezoelectric layer 132. The piezoelectric layer 132 may be implemented using a variety of materials such as lithium niobate, lithium tantalate, quartz, aluminum nitride, aluminum scandium nitride, or some combination thereof.

[0108] At 1104, at least one channel is etched across the surface of the piezoelectric layer. For example, the manufacturing process etches at least one channel 312 across the surface of the piezoelectric layer 132. Figure 6 or Figure 7 As shown, the channel 312 may correspond to a continuous channel across the track length of the surface acoustic wave filter 124 adjacent to the boundary of the active track region 504. Alternatively, as shown in FIG. Figure 8 or Fig. 9 As shown, channel 312 may correspond to one of a plurality of segmented channels 802 that are positioned adjacent a boundary of active track region 504 along the track length.

[0109] In some implementations, multiple channels 312 are etched in the surface of the piezoelectric layer 132. The multiple channels 312 can be located in the same trap region 506 (e.g., adjacent to the same boundary of the active track region 504) or in different trap regions 506 (e.g., adjacent to different boundaries of the active track region 504). The properties of the channels 312 (e.g., location, length, width, or depth) can be tailored to achieve a specific level of spurious mode suppression. In some implementations, the piezoelectric layer 132 is formed to have the channels 312 therein.

[0110] At 1106, a dielectric material is deposited within the at least one channel. For example, the manufacturing process deposits dielectric material 134 within at least one channel 312. In some cases, the manufacturing process fills at least one channel 312 with dielectric material 134 so that a surface of dielectric material 134 is substantially flush with a surface of piezoelectric layer 132. Dielectric material 134 may include tantalum oxide, silicon oxide, silicon dioxide, silicon nitride, hafnium oxide, aluminum oxide, tungsten trioxide, niobium pentoxide, or some combination or doped version thereof. The density and / or stiffness of dielectric material 134 may be tailored to achieve a particular level of stray mode suppression.

[0111] At 1108, an electrode structure is provided that at least partially covers the dielectric material. For example, the manufacturing process provides an electrode structure 130 that at least partially covers the dielectric material 134. The electrode structure 130 can partially cover the dielectric material 134, such as Figures 6 to 8 As shown, or completely covered with dielectric material 134, such as Fig. 9 In some implementations, the electrode structure 130 is in physical contact with the dielectric material 134 or is separated by another dielectric layer.

[0112] Some aspects are described below.

[0113] Aspect 1: A device, comprising:

[0114] A surface acoustic wave filter, the surface acoustic wave filter comprising:

[0115] a piezoelectric layer having at least one channel;

[0116] Electrode structure; and

[0117] A dielectric material, the dielectric material being disposed on at least one of the piezoelectric layers

[0118] In one channel, the dielectric material is at least partially covered by the electrode structure.

[0119] Aspect 2: The device according to aspect 1, wherein:

[0120] The electrode structure comprises:

[0121] A first busbar and a second busbar;

[0122] A first group of fingers extending from the first busbar toward the

[0123] Second busbar extension; and

[0124] a second set of fingers extending from the second busbar toward the first busbar; and

[0125] The at least one channel comprises:

[0126] a first channel adjacent ends of fingers associated with the first set of fingers; and

[0127] A second channel is provided adjacent to ends of fingers associated with the second set of fingers.

[0128] Aspect 3: The device according to aspect 1 or 2, wherein:

[0129] The electrode structure comprises at least one finger; and

[0130] The at least one channel has a longitudinal axis that is substantially orthogonal to the longitudinal axis of the at least one finger.

[0131] Aspect 4: The apparatus according to aspect 3, wherein:

[0132] The at least one channel includes a channel adjacent to a boundary of an active track region of the surface acoustic wave filter; and

[0133] The dielectric material disposed in the one channel is at least partially covered by the at least one finger.

[0134] Aspect 5: The apparatus according to any of the preceding aspects, wherein:

[0135] The electrode structure comprises a plurality of fingers; and

[0136] The dielectric material is at least partially covered by the plurality of fingers.

[0137] Aspect 6: The apparatus according to aspect 5, wherein:

[0138] The at least one channel includes two channels, the two channels being substantially parallel to each other and adjacent to a boundary of an active track region of the surface acoustic wave filter;

[0139] The dielectric material disposed in a first of the two channels is at least partially covered by the plurality of fingers; and

[0140] The dielectric material disposed in a second channel of the two channels is at least partially covered by the plurality of fingers.

[0141] Aspect 7: The apparatus according to aspect 5, wherein:

[0142] The at least one channel comprises a plurality of channels; and

[0143] The dielectric material disposed in each of the plurality of channels is at least partially covered by a corresponding finger of the plurality of fingers.

[0144] Aspect 8: The device according to aspect 7, wherein the plurality of channels are arranged along an axis associated with a direction of propagation of acoustic waves.

[0145] Aspect 9: The device of aspect 7 or 8, wherein the longitudinal axes of the plurality of channels are substantially orthogonal to the longitudinal axes of the plurality of fingers.

[0146] Aspect 10: The apparatus of any one of aspects 7 to 9, wherein the dielectric material disposed in each of the plurality of channels is completely covered by a corresponding finger of the plurality of fingers.

[0147] Aspect 11: The device according to any preceding aspect, wherein a surface of the dielectric material facing the electrode structure is substantially flush with a surface of the piezoelectric layer facing the electrode structure.

[0148] Aspect 12: The apparatus according to any of the preceding aspects, wherein:

[0149] The electrode structure has a spacing; and

[0150] The lateral axis of the dielectric material has a width between about 30% and 200% of the pitch.

[0151] Aspect 13: The device of any preceding aspect, wherein the thickness of the dielectric material is between about 5% and 100% of the length of twice the pitch of the electrode structure.

[0152] Aspect 14: The device of aspect 13, wherein the thickness of the dielectric material is about 50% of the length of twice the pitch of the electrode structure.

[0153] Aspect 15: The apparatus of aspect 13, wherein the thickness of the dielectric material is between about 5% and 20% of the length of twice the pitch of the electrode structure.

[0154] Aspect 16: The device of any preceding aspect, wherein the dielectric material comprises at least one of:

[0155] Tantalum oxide (Ta2O5);

[0156] Silicon oxide (SiO);

[0157] Silicon dioxide (SiO2);

[0158] Silicon nitride (Si3N4);

[0159] Hafnium oxide (HfO2);

[0160] Alumina (Al2O3);

[0161] Tungsten trioxide (WO3); or

[0162] Niobium pentoxide (Nb2O5).

[0163] Aspect 17: The apparatus according to any preceding aspect, wherein:

[0164] The surface acoustic wave filter includes a plurality of cascaded resonators; and

[0165] A resonator in the plurality of cascaded resonators includes the piezoelectric layer, the electrode structure, and the dielectric material.

[0166] Aspect 18: The apparatus according to any preceding aspect, wherein:

[0167] The surface acoustic wave filter comprises a substrate layer;

[0168] The substrate layer includes a compensation layer; and

[0169] The piezoelectric layer is arranged between the electrode structure and the compensation layer of the substrate layer.

[0170] Aspect 19: The device according to any preceding aspect, wherein the surface acoustic wave filter comprises a thin film surface acoustic wave filter.

[0171] Aspect 20: The apparatus of any one of Aspects 1 to 18, wherein the surface acoustic wave filter comprises a high-quality temperature-compensated surface acoustic wave filter.

[0172] Aspect 21: A device, comprising:

[0173] A surface acoustic wave filter configured to generate a

[0174] filtering a signal, the surface acoustic wave filter comprising:

[0175] means for converting the radio frequency signal into acoustic waves and converting the propagated acoustic waves into the filtered signal;

[0176] means for propagating said acoustic wave across a planar surface to produce said propagated acoustic wave;

[0177] and

[0178] Means for operating in piston mode, said means for operating being arranged in said means for propagating and at least partially covered by said means for converting.

[0179] Aspect 22: The apparatus of aspect 21, wherein the means for operating comprises means for attenuating transverse modes.

[0180] Aspect 23: The device according to aspect 21 or 22, wherein the means for operating is present in a trap region of the surface acoustic wave filter.

[0181] Aspect 24: A method for manufacturing a surface acoustic wave filter, the method comprising:

[0182] providing a piezoelectric layer;

[0183] etching at least one channel across a surface of the piezoelectric layer;

[0184] depositing a dielectric material within the at least one via; and

[0185] An electrode structure is provided that at least partially covers the dielectric material.

[0186] Aspect 25: The method of aspect 24, wherein the depositing of the dielectric material comprises filling the at least one channel with the dielectric material such that a surface of the dielectric material facing the electrode structure is substantially flush with the surface of the piezoelectric layer.

[0187] Aspect 26: A device, comprising:

[0188] a piezoelectric layer configured to propagate acoustic waves along a first axis, the piezoelectric layer having at least one recessed region having a longitudinal axis substantially parallel to the first axis; and

[0189] A dielectric material is located in the at least one recessed region, the dielectric material having at least one surface exposed.

[0190] Aspect 27: The apparatus according to Aspect 26, further comprising:

[0191] An electrode structure is in contact with the piezoelectric layer and the dielectric material.

[0192] Aspect 28: The apparatus according to Aspect 27, further comprising:

[0193] A surface acoustic wave filter comprises the piezoelectric layer, the dielectric material and the electrode structure.

[0194] Aspect 29: The device of aspect 28, wherein the dielectric material is present in a trap region of the surface acoustic wave filter.

[0195] Aspect 30: The apparatus according to Aspect 29, wherein:

[0196] The surface acoustic wave filter is configured to generate the acoustic wave so that the acoustic wave has a first velocity in an active track region of the surface acoustic wave filter and a second velocity in the trap region; and

[0197] The second speed is lower than the first speed.

[0198] Unless the context dictates otherwise, the use of the word "or" herein may be considered an "inclusive or" or use of a term that permits inclusion or application of one or more items linked by the word "or" (e.g., the phrase "A or B" may be interpreted as permitting only "A," only "B," or both "A" and "B"). As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items (including a single member). As an example, "at least one of a, b, or c" is intended to encompass: a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c). In addition, the items represented in the drawings and the terms discussed herein may indicate one or more items or terms, and thus the singular or plural forms of those items and terms may be referred to interchangeably in this written description. Finally, although the subject matter has been described in language specific to structural features or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including not necessarily being limited to the organization in which the features are arranged or the order in which the operations are performed.

Claims

1. A device, comprising: A surface acoustic wave filter, comprising: a piezoelectric layer having at least one channel; Electrode structure; and A dielectric material is disposed in the at least one channel of the piezoelectric layer, the dielectric material being at least partially covered by the electrode structure.

2. The device according to claim 1, wherein: The electrode structure comprises: A first busbar and a second busbar; a first set of fingers extending from the first busbar toward the second busbar; and a second set of fingers extending from the second busbar toward the first busbar; and The at least one channel comprises: a first channel adjacent ends of fingers associated with the first set of fingers; and A second channel is provided adjacent to ends of fingers associated with the second set of fingers.

3. The device according to claim 1, wherein: The electrode structure comprises at least one finger; and The at least one channel has a longitudinal axis that is substantially orthogonal to the longitudinal axis of the at least one finger.

4. The device according to claim 3, wherein: The at least one channel includes a channel adjacent to a boundary of an active track region of the surface acoustic wave filter; and The dielectric material disposed in the one channel is at least partially covered by the at least one finger.

5. The device according to claim 1, wherein: The electrode structure comprises a plurality of fingers; and The dielectric material is at least partially covered by the plurality of fingers.

6. The device according to claim 5, wherein: The at least one channel includes two channels, the two channels being substantially parallel to each other and adjacent to a boundary of an active track region of the surface acoustic wave filter; the dielectric material disposed in a first of the two channels being at least partially covered by the plurality of fingers; and The dielectric material disposed in a second channel of the two channels is at least partially covered by the plurality of fingers.

7. The device according to claim 5, wherein: The at least one channel comprises a plurality of channels; and The dielectric material disposed in each of the plurality of channels is at least partially covered by a corresponding finger of the plurality of fingers.

8. The device of claim 7, wherein the plurality of channels are arranged along an axis associated with a direction of acoustic wave propagation.

9. The device of claim 7, wherein the longitudinal axes of the plurality of channels are substantially orthogonal to the longitudinal axes of the plurality of fingers.

10. The apparatus of claim 7, wherein the dielectric material disposed in each of the plurality of channels is completely covered by the corresponding finger of the plurality of fingers.

11. The device of claim 1, wherein a surface of the dielectric material facing the electrode structure is substantially flush with a surface of the piezoelectric layer facing the electrode structure.

12. The device according to claim 1, wherein: The electrode structure has a spacing; and The lateral axis of the dielectric material has a width between about 30% and 200% of the pitch.

13. The device of claim 1, wherein the dielectric material has a thickness between about 5% and 100% of a length of twice the pitch of the electrode structures.

14. The device of claim 13, wherein the thickness of the dielectric material is about 50% of the length of twice the pitch of the electrode structure.

15. The device of claim 13, wherein the thickness of the dielectric material is between about 5% and 20% of the length of twice the pitch of the electrode structures.

16. The device of claim 1, wherein the dielectric material comprises at least one of: Tantalum oxide (Ta2O5); Silicon oxide (SiO); Silicon dioxide (SiO2); Silicon nitride (SiN); Hafnium oxide (HfO2); Alumina (Al2O3); Tungsten trioxide (WO3); or Niobium pentoxide (Nb2O5).

17. The device according to claim 1, wherein: The surface acoustic wave filter includes a plurality of cascaded resonators; and A resonator in the plurality of cascaded resonators includes the piezoelectric layer, the electrode structure, and the dielectric material.

18. The apparatus of claim 1, wherein: The surface acoustic wave filter comprises a substrate layer; The substrate layer includes a compensation layer; and The piezoelectric layer is arranged between the electrode structure and the compensation layer of the substrate layer.

19. The device of claim 1, wherein the surface acoustic wave filter comprises a thin film surface acoustic wave filter.

20. The apparatus of claim 1, wherein the surface acoustic wave filter comprises a high quality temperature compensated surface acoustic wave filter.

21. A device, comprising: A surface acoustic wave filter, the surface acoustic wave filter being configured to generate a filtered signal from a radio frequency signal, the surface acoustic wave filter comprising: means for converting the radio frequency signal into acoustic waves and converting the propagated acoustic waves into the filtered signal; means for propagating said acoustic wave across a planar surface to produce said propagated acoustic wave; and Means for operating in piston mode, said means for operating being arranged in said means for propagating and at least partially covered by said means for converting.

22. The apparatus of claim 21, wherein the means for operating comprises means for attenuating transverse modes.

23. The device of claim 21, wherein the means for operating is present in a trap region of the surface acoustic wave filter.

24. A method for manufacturing a surface acoustic wave filter, the method comprising: providing a piezoelectric layer; etching at least one channel across a surface of the piezoelectric layer; depositing a dielectric material within the at least one channel; as well as An electrode structure is provided that at least partially covers the dielectric material.

25. The method of claim 24, wherein the depositing of the dielectric material comprises filling the at least one channel with the dielectric material such that a surface of the dielectric material facing the electrode structure is substantially flush with the surface of the piezoelectric layer.

26. An apparatus, comprising: a piezoelectric layer configured to propagate acoustic waves along a first axis, the piezoelectric layer having at least one recessed region having a longitudinal axis substantially parallel to the first axis; and A dielectric material is located in the at least one recessed region, the dielectric material having at least one surface exposed.

27. The apparatus according to claim 26, further comprising: An electrode structure is in contact with the piezoelectric layer and the dielectric material.

28. The apparatus according to claim 27, further comprising: A surface acoustic wave filter comprises the piezoelectric layer, the dielectric material and the electrode structure.

29. The device of claim 28, wherein the dielectric material is present in a trap region of the surface acoustic wave filter.

30. The apparatus of claim 29, wherein: The surface acoustic wave filter is configured to generate the acoustic wave so that the acoustic wave has a first velocity in an active track region of the surface acoustic wave filter and a second velocity in the trap region; and The second speed is lower than the first speed.

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