In one example aspect, the present disclosure is directed to a method. The method includes receiving a workpiece having a conductive feature over a semiconductor substrate, forming a sacrificial material layer over the conductive feature, removing first portions of the sacrificial material layer to form line trenches and to expose a top surface of the conductive feature in one of the line trenches; forming line features in the line trenches, removing second portions of the sacrificial material layer to form gaps between the line features, and forming dielectric features in the gaps, the dielectric features enclosing an air gap.