An interconnection structure and method of forming the same are disclosed. A substrate is provided. A patterned layer is formed on the substrate and having at least a trench formed therein. A first dielectric layer is then formed on the patterned layer and sealing an air gap in the trench. Subsequently, a second dielectric layer is formed on the first dielectric layer and completely covering the patterned layer and the air gap. A curing process is then performed to the first dielectric layer and the second dielectric layer. A volume of the air gap is increased after the curing process.