A semiconductor structure including a first metal line and a second metal line in a dielectric layer, the first metal line and the second metal line are adjacent and within the same dielectric level; an air gap structure in the dielectric layer and between the first metal line and the second metal line, wherein the air gap structure includes an air gap oxide layer and an air gap; and a barrier layer between the air gap structure and the first metal line, wherein the barrier layer is an oxidized metal layer.