Air gap formation and integration using a patterning cap

Methods for patterning films and their resulting structures. In an embodiment, an amorphous carbon mask is formed over a substrate, such as a damascene layer. A spacer layer is deposited over the amorphous carbon mask and the spacer layer is etched to form a spacer and to expose the amorphous carbon mask. The amorphous carbon mask is removed selectively to the spacer to expose the substrate layer. A gap fill layer is deposited around the spacer to cover the substrate layer but expose the spacer. The spacer is removed selectively to form a gap fill mask over the substrate. The pattern of the gap fill mask is transferred, in one implementation, into a damascene layer to remove at least a portion of an IMD and form an air gap.