Low loss substrate for integrated passive devices

An electronic element incorporating an integrated passive device (IPD) and an active device, comprising:

• a substrate of a first material having a first thermal expansion coefficient (TEC) and having a first surface, wherein the substrate has therein a first portion adapted to receive the active device and a second portion adapted to receive the IPD;
• spaced-apart trenches of substantially a first width and a first depth in the substrate;
• columns of substantially undisturbed substrate material between the trenches and other portions of the substrate material beneath the trenches;
• dielectric having a second TEC formed in the trenches, wherein a substantially centrally located void is present in the dielectric extending from the first surface into the trenches but not in contact with the other portions of the substrate material beneath the trenches;
• solid inclusions filling the trenches, wherein the solid inclusions are electrically floating with respect to the substrate and the solid inclusions have a third TEC less than the second TEC;
• additional dielectric formed over the inclusions;
• and
• the IPD formed above the dielectric, the additional dielectric, and the inclusions, wherein the IPD is electrically isolated from the inclusions.