Process for reducing surface roughness of superconductor integrated circuit having a ground plane of niobium nitride of improved smoothness

The present invention relates to processes for reducing surface roughness of superconductor and semiconductor materials and more particularly, to processes for reducing the surface roughness of niobium nitride (NbN) and to superconductor integrated circuits formed on a ground plane of NbN. The invention is a process for reducing roughness of a surface of a superconductor material () having an undesirable surface roughness (and ) and a trilayer superconductor integrated circuit (). The process for reducing roughness of a surface of superconductor material having an undesirable surface roughness includes coating the surface with an oxide layer () to fill the undesirable surface roughness and to produce an exposed oxide surface () with a roughness less than the surface roughness; and etching the exposed oxide surface to remove a thickness of the oxide layer followed by removing at least a portion of the oxide layer filling the undesirable surface roughness and a portion of the surface of the superconductor material to produce an exposed etched surface () comprised of at least the superconductor material which has a surface roughness less than the undesirable surface roughness.