# US 7,609,129 B2 · Surface acoustic wave device, surface acoustic wave apparatus, and communications equipment > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,129 B2 - Document ID: US7609129B2 - Status: Granted - Kind: B2 - Application number: 11/190,515 - Filed: 2005-07-27 - Published: 2006-02-02 - Granted: 2009-10-27 - Earliest claimed: 2004-07-28 - Assignees: KYOCERA Corporation - Inventors: Yuuko Yokota; Yoshifumi Yamagata; Kiyohiro Iioka - Web page: https://patentgrep.com/patent/US7609129B2 ## CPC - H03H 9/1085: {the enclosure being defined by a non-uniform sealing mass covering the non-active sides of the SAW device} - H03H 9/02574: {of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate} - H03H 9/02614: {Treatment of substrates, e.g. curved, spherical, cylindrical substrates ensuring closed round-about circuits for the acoustical waves} - H03H 9/02952: {of parasitic capacitance} - H03H 9/02984: {Protection measures against damaging} - H03H 9/0576: {including surface acoustic wave [SAW] devices} - H03H 9/059: {consisting of mounting pads or bumps} - H03H 9/1092: {the enclosure being defined by a cover cap mounted on an element forming part of the surface acoustic wave [SAW] device on the side of the IDT's} - H03H 9/72: Networks using surface acoustic waves - H03H 9/725: {Duplexers} - H10W 90/724: {between a chip and a stacked insulating package substrate, interposer or RDL} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract A second substrate 21 composed of a material having a lower dielectric constant than that of a piezoelectric substrate 2 having a transmission-side filter region 12 and a receiving-side filter region 13 formed therein is joined to the other main surface of the piezoelectric substrate 2, and a conductor layer 22 is formed throughout the other main surface of the second substrate 21. The effective dielectric constant of the substrate is reduced, thereby making it possible to reduce a parasitic capacitance formed between an input electrode section 5 in the transmission-side filter region 12 and an output electrode section 6 in the receiving-side filter region 13 and to improve isolation characteristics. ## Claims ### Claim 1 A surface acoustic wave device in which an IDT electrode, an input electrode section, and an output electrode section are formed in a filter region on one main surface of a first substrate composed of a piezoelectric member, wherein a second substrate composed of a material having a lower dielectric constant than that of the first substrate is joined to the other main surface of the first substrate, and a conductor layer is formed on a surface of the second substrate opposite to the surface joined to the first substrate, and wherein the conductor layer is formed throughout the surface of the second substrate opposite to the surface joined to the first substrate, wherein the second substrate is a multilayer substrate. ### Claim 2 (depends on 1) The surface acoustic wave device according to claim 1, wherein the filter region comprises a transmission-side filter region and a receiving-side filter region, and the IDT electrode, the input electrode section, and the output electrode section are formed in each of the filter regions. ### Claim 3 (depends on 1) The surface acoustic wave device according to claim 1, wherein the second substrate is joined to the first substrate through an adhesive layer. ### Claim 4 (depends on 1) The surface acoustic wave device according to claim 1, if wherein the other main surface of the first substrate is a surface rougher than the one main surface of the first substrate. ### Claim 5 (depends on 1) The surface acoustic wave device according to claim 1, wherein the second substrate is composed of a material having a lower coefficient of thermal expansion than that of the first substrate composed of a piezoelectric member. ### Claim 6 (depends on 1) The surface acoustic wave device according to claim 1, wherein the second substrate is composed of a material selected from silicon, glass, sapphire, quartz, crystal, resin, and ceramics. ### Claim 7 (depends on 1) The surface acoustic wave device according to claim 1, wherein the relationship between the thickness d2 of the second substrate and the thickness d1 of the first substrate is d2>d1. ### Claim 8 A surface acoustic wave apparatus, comprising: a surface acoustic wave device having an IDT electrode, an input electrode section, and an output electrode section that are formed in a filter region on one main surface of a first substrate composed of a piezoelectric member, a second substrate composed of a material having a lower dielectric constant than that of the first substrate joined to the other main surface of the first substrate, and a conductor layer formed throughout a surface of the second substrate opposite to the surface joined to the first substrate, wherein the second substrate is a multilayer substrate, and a mounting substrate, wherein the surface acoustic wave device is mounted on the mounting substrate with the main surface, on which the filter region is formed, of the first substrate in the surface acoustic wave device opposed thereto. ### Claim 9 (depends on 8) The surface acoustic wave device according to claim 8, wherein the other main surface of the first substrate is a surface rougher than the one main surface of the first substrate. ### Claim 10 (depends on 8) Communications equipment comprising at least one of a receiving circuit and a transmission circuit having the surface acoustic wave apparatus according to claim 8. ### Claim 11 (depends on 8) Communications equipment, wherein the surface acoustic wave apparatus according to claim 8 is used as a branching filter.