Middle-Of-Line Interconnect Structure Having Air Gap And Method Of Fabrication Thereof

A device comprising:

• a first oxide layer disposed over a substrate;
• a second oxide layer disposed over the first oxide layer;
• a third oxide layer disposed over the second oxide layer;
• a device-level contact disposed in and extending through the first oxide layer and physically contacting an IC device feature formed on the substrate;
• a ruthenium structure disposed in the second oxide layer and physically contacting the device-level contact, wherein an air gap is disposed between sidewalls of the ruthenium structure and the second oxide layer;
• and
• a via disposed in the third oxide layer and the second oxide layer, wherein the via physically contacts the ruthenium structure.

A method comprising:

• forming a ruthenium structure over and physically contacting a device-level contact;
• forming a dummy contact spacer layer along sidewalls of the ruthenium structure;
• after forming an insulator layer over the dummy contact spacer layer, removing the dummy contact spacer layer from the sidewalls of the ruthenium structure to form an air gap between the sidewalls of the ruthenium structure and the insulator layer;
• and
• forming a via that physically contacts the ruthenium structure.