1. A nanoscale switching device comprising: a first electrode of a nanoscale width; a second electrode of a nanoscale width; an active region disposed between the first and second electrodes, the active region containing a switching material; an area within the active region that constrains current flow between the first electrode and the second electrode to a central portion of the active region; and an interlayer dielectric layer formed of a dielectric material and disposed between the first and second electrodes outside the active region.