Effect of a Buffer Layer on the Surface Acoustic Wave Characteristics of Pb(Zr, Ti)O3 Film/Buffer Layer/Semiconductor Substrate Structures

The effect of a buffer layer on the surface acoustic wave properties of Pb(Zr, Ti)O3 (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 floating-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 h K 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.