An embodiment of a device includes a semiconductor substrate, a transistor formed at the first substrate surface, a first conductive feature formed over the first substrate surface and electrically coupled to the transistor, and a second conductive feature covering only a portion of the second substrate surface to define a first conductor-less region. A cavity vertically aligned with the first conductive feature within the first conductor-less region extends into the semiconductor substrate. A dielectric medium may be disposed within the cavity and have a dielectric constant less than a dielectric constant of the semiconductor substrate. A method for forming the device may include forming a semiconductor substrate, forming a transistor on the semiconductor substrate, forming the first conductive feature, forming the second conductive feature, forming the conductor-less region, forming the cavity, and filling the cavity with the dielectric medium.