An integrated circuit is formed by forming an isolation trench through at least a portion of an interconnect region, at least 40 microns deep into a substrate of the integrated circuit, leaving at least 200 microns of substrate material under the isolation trench. Dielectric material is formed in the isolation trench at a substrate temperature no greater than 320° C. to form an isolation structure which separates an isolated region of the integrated circuit from at least a portion of the substrate. The isolated region contains an isolated component. The isolated region of the integrated circuit may be a region of the substrate, and/or a region of the interconnect region. The isolated region may be a first portion of the substrate which is laterally separated from a second portion of the substrate. The isolated region may be a portion of the interconnect region above the isolation structure.