A method of forming air gaps between adjacent raised features on a substrate includes forming a carbon-containing material in a bottom region between the adjacent raised features using a flowable deposition process. The method also includes forming a silicon-containing film over the carbon-containing material using a flowable deposition process, where the silicon-containing film fills an upper region between the adjacent raised features and extends over the adjacent raised features. The method also includes curing the carbon-containing material and the silicon-containing material at an elevated temperature for a period of time to form the air gaps between the adjacent raised features.