Suspended transmission line structures in back end of line processing

A back end of line microstrip transmission line structure, comprising:

• a signal transmission line formed on one metallization level;
• a ground plane formed on another metallization level;
• an air gap disposed between said signal transmission line and said ground plane, said air gap formed within an interlevel dielectric layer;
• one of said signal transmission line and said ground plane further comprising a plurality of access holes formed therethrough to provide removal access to a sacrificial material used to define said air gap, said plurality of access holes being arranged along a direction parallel to conductor edges of one of said signal transmission line and said ground plane;
• and
• a support structure disposed directly beneath said one of said signal transmission line and said ground plane having a plurality of access holes, said support structure;
• consisting of material entirely from said interlevel dielectric layer, and wherein a bottom surface of said support structure is in contact with the other of said signal transmission line and said ground plane.