Integrated circuit structure with semiconductor-based isolation structure and methods to form same

An integrated circuit (IC) structure, comprising:

• a first active semiconductor region on a substrate, wherein the first active semiconductor region includes a doped semiconductor material;
• a device on the first active semiconductor region;
• a semiconductor-based isolation structure on the substrate and including a first sidewall horizontally adjacent to the first active semiconductor region;
• a shallow trench isolation (STI) structure on the semiconductor-based isolation structure and including a first sidewall horizontally abutting the first active semiconductor region;
• and
• a second active semiconductor region on the substrate and horizontally adjacent to a second sidewall of the semiconductor-based isolation structure and a second sidewall of the STI structure, wherein the silicon-based dielectric structure and the STI structure physically and electrically isolate the second active semiconductor region from the first active semiconductor region.

A method of forming an integrated circuit (IC) structure, the method comprising:

• forming a first active semiconductor region and a second active semiconductor region within a semiconductor substrate, wherein a non-active semiconductor region of the semiconductor substrate separates the first active semiconductor region from the second active semiconductor region;
• forming a semiconductor-based isolation structure within the non-active semiconductor region of the semiconductor substrate, and between the first active semiconductor region and the second active semiconductor region, wherein an upper surface of the semiconductor-based isolation structure is below an upper surface of the first active semiconductor region and the second active semiconductor region;
• and
• forming a shallow trench isolation (STI) structure on the semiconductor-based isolation structure between the first active semiconductor region and the second active semiconductor region.