Design structure embodied in a machine readable medium for designing, manufacturing, or testing a design. The design structure includes semiconductor device structures characterized by reduced junction capacitance and drain induced barrier lowering. The semiconductor device structure of the design structure includes a semiconductor layer and a dielectric layer disposed between the semiconductor layer and the substrate. The dielectric layer includes a first dielectric region with a first dielectric constant and a second dielectric region with a second dielectric constant that is greater than the first dielectric constant.