Air gap and air spacer pinch off

A method for forming a semiconductor device, the method comprising:

• forming a trench in a first dielectric layer;
• forming a first liner comprising a first material on the first dielectric layer, the first liner partially filling the trench;
• forming a second liner comprising a second material on the first liner;
• forming a contact in the trench, the second liner between the contact and the first dielectric layer;
• and
• self-forming a third liner comprising a third material by diffusing a portion of the second material through the first liner, wherein the first material is cobalt, the second material is manganese, and the third material is a metal silicate, wherein the metal silicate is selected from a group consisting of MnSiOx, MnSiCOx, and MnSiCNO.

A semiconductor device comprising:

• a first and a second contact formed on a first dielectric layer, the first contact adjacent to the second contact;
• a first cap on a surface of the first contact and a second cap on a surface of the second contact;
• a barrier liner over the first and second contacts, the first and second caps, and the first dielectric layer, the barrier liner partially filling a trench between the first and second contacts;
• a second dielectric layer over the barrier liner;
• an air gap in the trench, the air gap trapped between the barrier liner and the second dielectric layer;
• and
• self-forming barrier layers, the self-forming barrier layers formed between portions of the barrier liner and the first and second dielectric layers, wherein the barrier liner comprises MnNy and the self-forming barrier layers comprise MnNySiCNO.