Device structures with hyper-abrupt p-n junctions, methods of forming hyper-abrupt p-n junctions, and design structures for an integrated circuit containing devices structures with hyper-abrupt p-n junctions. The hyper-abrupt p-n junction is defined in a SOI substrate by implanting a portion of a device layer to have one conductivity type and then implanting a portion of this doped region to have an opposite conductivity type. The counterdoping defines the hyper-abrupt p-n junction. A gate structure carried on a top surface of the device layer operates as a hard mask during the ion implantations to assist in defining a lateral boundary for the hyper-abrupt-n junction.