Filter and multi-filter

1. A filter comprising:

a ladder filter portion formed on a first piezoelectric substrate; and

a multi-mode filter portion connected to the ladder filter portion and formed on a second piezoelectric substrate different from the first piezoelectric substrate,

wherein the ladder filter portion and the multi-mode filter portion constitute a single passband, and

wherein an electrode thickness of the ladder filter portion is different from an electrode thickness of the multi-mode filter portion.

2. The filter according to claim 1 , wherein a cut-angle of the first piezoelectric substrate is different from a cut-angle of the second piezoelectric substrate.

3. The filter according to claim 1 , wherein a thickness of the first piezoelectric substrate is different from a thickness of the second piezoelectric substrate.

4. The filter according to claim 3 ,

wherein the ladder filter portion comprises a plurality of resonators connected in a ladder form,

wherein the resonators each include an IDT electrode having a plurality of electrode fingers arranged at a pitch p, and

wherein the thickness of the first piezoelectric substrate is less than or equal to 2p.

5. The filter according to claim 1 , wherein

an end of the ladder filter portion is connected to an antenna terminal,

the ladder filter portion comprises resonators in each of which a plurality of electrode fingers are repetitively arranged,

the first piezoelectric substrate for the ladder filter portion has a thickness that is less than or equal to twice a pitch at which the electrode fingers are repetitively arranged, and

the ladder filter portion further comprises a support substrate directly or indirectly connected to the first piezoelectric substrate.

6. A multi-filter comprising:

a first filter as which the filter according to claim 1 is used; a second filter; and a third filter,

wherein a center frequency of a passband of the first filter takes a value between center frequencies of the second filter and the third filter, and

wherein the first substrate or the second substrate is shared with the second filter or the third filter.

7. The multi-filter according to claim 6 , wherein the second filter is a ladder filter and shares the first substrate.

8. The multi-filter according to claim 6 , wherein the third filter comprises a multi-mode filter and shares the second substrate.

9. A filter comprising:

a ladder filter portion formed on a first piezoelectric substrate; and

a multi-mode filter portion connected to the ladder filter portion and formed on a second piezoelectric substrate different from the first piezoelectric substrate,

wherein the ladder filter portion and the multi-mode filter portion constitute a single passband, and

wherein a cut-angle of the first piezoelectric substrate is different from a cut-angle of the second piezoelectric substrate.

10. The filter according to claim 9 , wherein a thickness of the first piezoelectric substrate is different from a thickness of the second piezoelectric substrate.

11. The filter according to claim 9 , wherein

an end of the ladder filter portion is connected to an antenna terminal,

the ladder filter portion comprises resonators in each of which a plurality of electrode fingers are repetitively arranged,

the first piezoelectric substrate for the ladder filter portion has a thickness that is less than or equal to twice a pitch at which the electrode fingers are repetitively arranged, and

the ladder filter portion further comprises a support substrate directly or indirectly connected to the first piezoelectric substrate.

12. A multi-filter comprising:

a first filter as which the filter according to claim 9 is used; a second filter; and a third filter,

wherein a center frequency of a passband of the first filter takes a value between center frequencies of the second filter and the third filter, and

wherein the first substrate or the second substrate is shared with the second filter or the third filter.

13. The multi-filter according to claim 12 , wherein the second filter is a ladder filter and shares the first substrate.

14. The multi-filter according to claim 12 , wherein the third filter comprises a multi-mode filter and shares the second substrate.

15. A filter comprising:

a ladder filter portion formed on a first piezoelectric substrate; and

a multi-mode filter portion connected to the ladder filter portion and formed on a second piezoelectric substrate different from the first piezoelectric substrate,

wherein the ladder filter portion and the multi-mode filter portion constitute a single passband, and

wherein a thickness of the first piezoelectric substrate is different from a thickness of the second piezoelectric substrate.

16. The filter according to claim 15 ,

wherein the ladder filter portion comprises a plurality of resonators connected in a ladder form,

wherein the resonators each include an IDT electrode having a plurality of electrode fingers arranged at a pitch p, and

wherein the thickness of the first piezoelectric substrate is less than or equal to 2p.

17. The filter according to claim 15 , wherein

an end of the ladder filter portion is connected to an antenna terminal,

the ladder filter portion comprises resonators in each of which a plurality of electrode fingers are repetitively arranged,

the first piezoelectric substrate for the ladder filter portion has a thickness that is less than or equal to twice a pitch at which the electrode fingers are repetitively arranged, and

the ladder filter portion further comprises a support substrate directly or indirectly connected to the first piezoelectric substrate.

18. A multi-filter comprising:

a first filter as which the filter according to claim 15 is used; a second filter; and a third filter,

wherein a center frequency of a passband of the first filter takes a value between center frequencies of the second filter and the third filter, and

wherein the first substrate or the second substrate is shared with the second filter or the third filter.

19. The multi-filter according to claim 18 , wherein the second filter is a ladder filter and shares the first substrate.

20. The multi-filter according to claim 18 , wherein the third filter comprises a multi-mode filter and shares the second substrate.