Semiconductor devices, such as photonics devices, employ substantially curved-shaped Silicon-Germanium (SiGe) structures and are fabricated using zero-change CMOS fabrication process technologies. In one example, a closed-loop resonator waveguide-coupled photodetector includes a silicon resonator structure formed in a silicon substrate, interdigitated n-doped well-implant regions and p-doped well-implant regions forming multiple silicon p-n junctions around the silicon resonator structure, and a closed-loop SiGe photocarrier generation region formed in a pocket within the interdigitated n-doped and p-doped well implant regions. The closed-loop SiGe region is located so as to substantially overlap with an optical mode of radiation when present in the silicon resonator structure, and traverses the multiple silicon p-n junctions around the silicon resonator structure. Electric fields arising from the respective p-n silicon junctions significantly facilitate a flow of the generated photocarriers between electric contact regions of the photodetector.