Surface acoustic wave device and duplexer having transmission/reception filter using same

1. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an IDT electrode on the piezoelectric substrate; wherein

the IDT electrode includes a first conductor layer, and a second conductor layer between the piezoelectric substrate and the first conductor layer; and

the first conductor layer is inside a region in which the second conductor layer is provided in plan view to suppress diffusion between the piezoelectric substrate and the first conductor layer when a voltage is applied to the IDT electrode.

2. The surface acoustic wave device according to claim 1 , wherein

the piezoelectric substrate includes LiNbO 3 ;

the first conductor layer includes Cu or a metal alloy including Cu; and

the second conductor layer includes one metal selected from a group consisting of Ni—Cr, Ni and Cr.

3. The surface acoustic wave device according to claim 1 , wherein the IDT electrode includes:

first electrode fingers; and

second electrode fingers that are adjacent to the first electrode fingers; and

a relation 0.01L≤R<0.5W is satisfied, where R is a width between an edge of the first conductor layer and an edge of the second conductor layer, L is a width of each of the first electrode fingers and W is a spacing between each of the first electrode fingers and an adjacent one of the second electrode fingers.

4. The surface acoustic wave device according to claim 1 , wherein a relation 10 nm≤R<500 nm is satisfied, where R represents a width between an edge of the first conductor layer and an edge of the second conductor layer.

5. The surface acoustic wave device according to claim 3 , further comprising:

a third conductor layer between the first conductor layer and the second conductor layer; wherein

the third conductor layer includes a metal other than Cu or a metal alloy that does not include Cu.

6. The surface acoustic wave device according to claim 3 , further comprising:

a third conductor layer between the first conductor layer and the second conductor layer; wherein

the third conductor layer includes one metal selected from a group consisting of Pt, Au, Ag, Ta, W, Ni and Mo or a metal alloy including at least two of Pt, Au, Ag, Ta, W, Ni and Mo.

7. The surface acoustic wave device according to claim 1 , further comprising:

an insulating layer that covers the IDT electrode.

8. A duplexer comprising:

a transmission-side filter that includes a transmission-side terminal; and

a reception-side filter that includes a reception-side terminal; wherein

the surface acoustic wave device according to claim 1 is connected in parallel with an initial stage of the transmission-side terminal.

9. The duplexer according to claim 8 , wherein

the piezoelectric substrate includes LiNbO 3 ;

the first conductor layer includes Cu or a metal alloy including Cu; and

the second conductor layer includes one metal selected from a group consisting of Ni—Cr, Ni and Cr.

10. The duplexer according to claim 8 , wherein the IDT electrode includes:

first electrode fingers; and

second electrode fingers that are adjacent to the first electrode fingers; and

a relation 0.01L≤R<0.5W is satisfied, where R is a width between an edge of the first conductor layer and an edge of the second conductor layer, L is a width of each of the first electrode fingers and W is a spacing between each of the first electrode fingers and an adjacent one of the second electrode fingers.

11. The duplexer according to claim 8 , wherein a relation 10 nm≤R<500 nm is satisfied, where R represents a width between an edge of the first conductor layer and an edge of the second conductor layer.

12. The duplexer according to claim 10 , wherein the surface acoustic wave device further comprises:

a third conductor layer between the first conductor layer and the second conductor layer; wherein

the third conductor layer includes a metal other than Cu or a metal alloy that does not include Cu.

13. The duplexer according to claim 10 , wherein the surface acoustic wave device further comprises:

a third conductor layer between the first conductor layer and the second conductor layer; wherein

the third conductor layer includes one metal selected from a group consisting of Pt, Au, Ag, Ta, W, Ni and Mo or a metal alloy including at least two of Pt, Au, Ag, Ta, W, Ni and Mo.

14. The duplexer according to claim 8 , further comprising:

an insulating layer that covers the IDT electrode.

15. A duplexer comprising:

a transmission-side filter that includes a transmission-side terminal; and

a reception-side filter that includes a reception-side terminal; wherein

a surface acoustic wave device unit in which a plurality of the surface acoustic wave device according to claim 1 are longitudinally coupled with each other is connected to an initial stage of the reception-side terminal.

16. The duplexer according to claim 15 , wherein

the piezoelectric substrate includes LiNbO 3 ;

the first conductor layer includes Cu or a metal alloy including Cu; and

the second conductor layer includes one metal selected from a group consisting of Ni—Cr, Ni and Cr.

17. The duplexer according to claim 15 , wherein the IDT electrode includes:

first electrode fingers; and

second electrode fingers that are adjacent to the first electrode fingers; and

a relation 0.01L≤R<0.5W is satisfied, where R is a width between an edge of the first conductor layer and an edge of the second conductor layer, L is a width of each of the first electrode fingers and W is a spacing between each of the first electrode fingers and an adjacent one of the second electrode fingers.

18. The duplexer according to claim 15 , wherein a relation 10 nm≤R<500 nm is satisfied, where R represents a width between an edge of the first conductor layer and an edge of the second conductor layer.

19. The duplexer according to claim 17 , wherein the surface acoustic wave device further comprises:

a third conductor layer between the first conductor layer and the second conductor layer; wherein

the third conductor layer includes a metal other than Cu or a metal alloy that does not include Cu.

20. The duplexer according to claim 17 , wherein the surface acoustic wave device further comprises:

a third conductor layer between the first conductor layer and the second conductor layer; wherein

the third conductor layer includes one metal selected from a group consisting of Pt, Au, Ag, Ta, W, Ni and Mo or a metal alloy including at least two of Pt, Au, Ag, Ta, W, Ni and Mo.

21. The duplexer according to claim 15 , further comprising:

an insulating layer that covers the IDT electrode.