Effect of a buffer layer on the surface acoustic wave characteristics of Pb(Zr,Ti)O-3 film/buffer layer/semiconductor substrate structures

The effect of a buffer layer on the surface acoustic wave properties of Pb(Zr, Ti)O-3 (PZT) film/buffer layer/semiconductor substrate structures was examined theoretically. Large coupling coefficients (2.8-3.4%) can be obtained when the interdigital transducer (IDT) is on top of the PZT film, with (type 4) and without (type 3) the Boating-plane electrode at the PZT film-buffer layer interface. In the type 4 IDT configuration, there exists a minor peak of the coupling coefficient when the hK value of the PZT film is about 0.3. The minor peak values of the coupling coefficient (0.62-0.93%) decrease when we increase the thickness of the buffer layer from 0 to 0.25. These results could be useful for the further development of ferroelectric devices, semiconductor devices and SAW devices on the same substrate.