Elastic wave device and manufacturing method for same

1. An elastic wave device comprising:

a support layer including a through-hole or a recess opened at an upper surface thereof;

a piezoelectric thin film arranged on the support layer to extend above the recess or the through-hole of the support layer; and

an IDT electrode provided on at least one of upper and lower surfaces of the piezoelectric thin film in a region of the piezoelectric thin film that extends above the recess or the through-hole; wherein

an elastic wave propagating in the piezoelectric thin film is a secondary mode of a plate wave that contains a U1 component as a main component of displacement;

a propagation velocity of the secondary mode of the plate wave is about 7000 meters per second or more;

the piezoelectric thin film is made of LiTaO 3 ; and

Euler angles (φ, θ, ψ) of the LiTaO 3 fall within any of ranges represented by regions R 1 to R 7 surrounded by solid lines in FIGS. 4 to 10 .

2. The elastic wave device according to claim 1 , wherein

the IDT electrode is made of Al or an alloy containing Al as a main component;

a film thickness of the IDT electrode is H; and

H≦about 0.08λ, where λ is a wavelength of the secondary mode of the plate wave, which contains mainly the U1 component.

3. The elastic wave device according to claim 1 , further comprising a dielectric film laminated on at least one of the upper and lower surfaces of the piezoelectric thin film, wherein a coefficient of linear expansion of the dielectric film is smaller than a coefficient of linear expansion of LiTaO 3 .

4. The elastic wave device according to claim 3 , wherein the dielectric film is made of silicon oxide.

5. The elastic wave device according to claim 3 , wherein the IDT electrode is provided on the upper surface of the piezoelectric thin film, the dielectric film is provided on the lower surface of the piezoelectric thin film, and the dielectric film is made of a dielectric material arranged to apply stress in a tensile direction to the piezoelectric thin film.

6. The elastic wave device according to claim 1 , wherein electrical resistance between a pair of the IDT electrodes is equal to or more than about 50 times a terminal impedance of an electric circuit to which the elastic wave device is connected, and equal to or less than about 1 MΩ.

7. The elastic wave device according to claim 1 , wherein a thickness of the piezoelectric thin film is in a range of equal to or more than about 50 nm and equal to or less than about 0.3λ, where λ a wavelength of the secondary mode of the plate wave, which contains mainly the U1 component.

8. An elastic wave device including a plurality of elastic wave devices according to claim 1 .

9. The elastic wave device according to claim 8 , wherein each of the plurality of elastic wave devices further comprises a dielectric film laminated on at least one of the upper and lower surfaces of the piezoelectric thin film, a coefficient of linear expansion of the dielectric film is smaller than a coefficient of linear expansion of LiTaO 3 .

10. A manufacturing method for the elastic wave device according to claim 1 , the method comprising the steps of:

injecting ions into a LiTaO 3 substrate from a surface thereof, thus forming an ion-injected portion on one surface side of the LiTaO 3 substrate;

forming a sacrificial layer in a portion of the surface of the LiTaO 3 substrate on the ion-injected side;

forming, as a support layer, an insulator to cover the surface of the LiTaO 3 substrate on the ion-injected side and the sacrificial layer;

separating the LiTaO 3 substrate at the ion-injected portion by heating, thus forming a structure of a piezoelectric thin film separated from the LiTaO 3 substrate;

causing the sacrificial layer to disappear, thus forming a recess in the support layer at a position under the piezoelectric thin film; and

forming an IDT electrode on at least one of upper and lower surfaces of the piezoelectric thin film.

11. An elastic wave device comprising:

a support layer including a through-hole or a recess opened at an upper surface thereof;

a piezoelectric thin film arranged on the support layer to extend above the recess or the through-hole of the support layer; and

an IDT electrode provided on at least one of upper and lower surfaces of the piezoelectric thin film in a region of the piezoelectric thin film that extends above the recess or the through-hole; wherein

a secondary mode of a plate wave, which contains a U1 component as a main component of displacement, is utilized, the piezoelectric thin film is made of LiTaO 3 , and Euler angles (φ, θ, ψ) of the LiTaO 3 fall within specific ranges, where φ is in a range of about 0° to about 30° and θ is in a range of about 0° to about 55° or a range of about 140° to about 180°;

when θ is in a range of about 0° to about 55°, ψ is in a range of about 180° to about 110°, a range of about 100° to about 50°, or a range of about 40° to about 0°;

when θ is in a range of about 140° to about 180°, ψ is in a range of about 180° to about 20° or a range of about 10° to about 0°; and

a propagation velocity of the secondary mode of the plate wave is about 7000 meters per second or more.

12. The elastic wave device according to claim 11 , wherein

φ is in a range of about 0° to about 2.5° and θ is in a range of about 0° to about 55° or a range of about 150° to about 180°;

when θ is in a range of about 0° to about 55°, ψ is in a range of about 180° to about 140°, a range of about 100° to about 80°, or a range of about 40° to about 0°; and

when θ is in a range of about 150° to about 180°, ψ is in a range of about 160° to about 65° or a range of about 50° to about 20°.

13. The elastic wave device according to claim 11 , wherein φ is in a range of about 2.5° to about 7.5° and θ is in a range of about 0° to about 55° or a range of about 150° to about 180°;

when θ is in a range of about 0° to about 55°, ψ is in a range of about 180° to about 135°, a range of about 95° to about 75°, or a range of about 35° to about 0°; and

when θ is in a range of about 150° to about 180°, ψ is in a range of about 165° to about 70° or a range of about 50° to about 25°.

14. The elastic wave device according to claim 11 , wherein

φ is in a range of about 7.5° to about 12.5° and θ is in a range of about 0° to about 50° or a range of about 150° to about 180°;

when θ is in a range of about 0° to about 50°, ψ is in a range of about 180° to about 130°, a range of about 90° to about 70°, or a range of about 30° to about 0°; and

when θ is in a range of about 150° to about 180°, ψ is in a range of about 170° to about 80° or a range of about 55° to about 30°.

15. The elastic wave device according to claim 11 , wherein φ is in a range of about 12.5° to about 17.5° and θ is in a range of about 0° to about 50° or a range of about 150° to about 180°;

when θ is in a range of about 0° to about 50°, ψ is in a range of about 180° to about 125°, a range of about 85° to about 65°, or a range of about 25° to about 0°; and

when θ is in a range of about 150° to about 180°, ψ is in a range of about 175° to about 85°, or a range of about 60° to about 35°.

16. The elastic wave device according to claim 11 , wherein

φ is in a range of about 17.5° to about 22.5° and θ is in a range of about 0° to about 50° or a range of about 145° to about 180°;

when θ is in a range of about 0° to about 50°, ψ is in a range of about 180° to about 120°, a range of about 80° to about 60°, or a range of about 20° to about 0°; and

when θ is in a range of about 150° to about 180°, if Is in a range of about 180° to about 95°, a range of about 60° to about 40°, or about 0°.

17. The elastic wave device according to claim 11 , wherein

φ is in a range of about 22.5° to about 27.5° and θ is in a range of about 0° to about 45° or a range of about 145° to about 180°;

when θ is in a range of about 0° to about 45°, ψ is in a range of about 180° to about 115°, a range of about 75° to about 55°, or a range of about 15° to about 0°; and

when θ is in a range of about 145° to about 180°, ψ is in a range of about 180° to about 105°, a range of about 65° to about 45°, or a range of about 5° to about 0°.

18. The elastic wave device according to claim 11 , wherein

φ is in a range of about 27.5° to about 30° and θ is in a range of about 0° to about 40° or a range of about 140° to about 180°;

when θ is in a range of about 0° to about 40°, ψ is in a range of about 175° to about 110°, a range of about 70° to about 50°, or a range of about 10° to about 5°; and

when θ is in a range of about 140° to about 180°, ψ is in a range of about 175° to about 110°, a range of about 70° to about 50°, or a range of about 10° to about 5°.

19. The elastic wave device according to claim 17 , wherein the IDT electrode of each of the plurality of elastic wave devices is provided on the upper surface of the piezoelectric thin film, the dielectric film is provided on the lower surface of the piezoelectric thin film, and the dielectric film is made of a dielectric material arranged to apply stress in a tensile direction to the piezoelectric thin film.