Thermally-isolated silicon-based integrated circuits and related methods

A thermally-isolated integrated circuit assembly formed on a silicon-based substrate having a back face that is free of etched openings, comprising:

• a piezoelectric resonator;
• a body of dielectric material;
• a support bar;
• a CMOS integrated circuit;
• a base layer of silicon;
• a base layer of silicon oxide above and contiguous to the silicon base layer;
• and
• an active silicon layer above and contiguous to the silicon oxide base layer;
• wherein:
• the CMOS integrated circuit comprises at least one device defined in the active silicon layer and further comprises a plurality of metallization layers that overlie the active silicon layer and are embedded in an interlayer dielectric;
• a lower cavity is defined within the silicon base layer;
• the body of dielectric material is suspended over the lower cavity by the support bar;
• the CMOS integrated circuit is encased on top, bottom, and all sides by the body of dielectric material;
• an upper cavity is defined in the top of the body of dielectric material;
• the piezoelectric resonator is suspended over the upper cavity and electrically connected to the CMOS integrated circuit through vertical electrical conductors extending within the body of dielectric material;
• the upper and lower cavities are interconnected by trenches in the body of dielectric material;
• and
• the support bar is formed in the silicon-based substrate to provide physical contact between the silicon-based substrate and the body of dielectric material.