Surface acoustic wave (SAW) resonator having trap-rich region

A surface acoustic wave (SAW) resonator device, comprising:

• a semiconductor substrate having a first surface and a second surface, the semiconductor substrate comprising a bulk region and a surface region wherein the surface region has a high trap density and a reduced carrier mobility compared to the bulk region, wherein the first surface of the semiconductor substrate comprises a plurality of features;
• a piezoelectric layer disposed over the semiconductor substrate, the piezoelectric layer having a first surface and a second surface;
• a plurality of electrodes disposed over the first surface of the piezoelectric layer, the plurality of electrodes configured to generate surface acoustic waves in the piezoelectric layer;
• and
• a layer having a first surface and a second surface, the layer being disposed between the first surface of the semiconductor substrate and the second surface of the piezoelectric layer, wherein the plurality of features each have a height of approximately one-fourth of a wavelength (¼λ) of a spurious mode, and the plurality of features reflect acoustic waves and reduce an incidence of spurious modes in the piezoelectric layer.

A surface acoustic wave (SAW) resonator device, comprising:

• a semiconductor substrate having a first surface and a second surface, the semiconductor substrate comprising a bulk region and a surface region wherein the surface region has a high trap density and a reduced carrier mobility compared to the bulk region;
• a piezoelectric layer disposed over the semiconductor substrate, the piezoelectric layer having a first surface and a second surface, wherein the second surface of the piezoelectric layer comprises a plurality of features;
• a plurality of electrodes disposed over the first surface of the piezoelectric layer, the plurality of electrodes configured to generate surface acoustic waves in the piezoelectric layer;
• and
• a layer having a first surface and a second surface, the layer being disposed between the first surface of the semiconductor substrate and the second surface of the piezoelectric layer, wherein the plurality of features each have a height of approximately one-fourth of a wavelength (¼λ) of a spurious mode, and the plurality of features reflect acoustic waves and reduce an incidence of spurious modes in the piezoelectric layer.