A method for forming a semiconductor structure includes forming an isolation region in a semiconductor substrate; forming a conductive layer over the isolation region; forming a first dielectric layer over the conductive layer; forming a plurality of conductive vias extending through the first dielectric layer to the conductive layer and electrically contacting the conductive layer; forming a second dielectric layer over the first dielectric layer; and forming a conductive ground plane in the second dielectric layer. Each of the plurality of conductive vias is in electrical contact with the conductive ground plane, and the conductive ground plane includes an opening, wherein the opening is located directly over the conductive layer. At least one interconnect layer may be formed over the second dielectric layer and may include a transmission line which transmits a signal having a frequency of at least 30 gigahertz.