An interconnect structure includes a dielectric layer, a conductive feature, a conductive layer, a capping layer, a support layer and an etch stop layer. The conductive feature is disposed in the dielectric layer. A first portion of the conductive layer is disposed over the first conductive feature, and a second portion of the conductive layer is disposed over the dielectric layer. A first portion of the capping layer is in contact with the first portion of the conductive layer, a second portion of the capping layer is in contact with the second portion of the conductive layer, and a third portion of the capping layer is in contact with the dielectric layer. An air gap is defined by the support layer and the capping layer. The etch stop layer is disposed over the second portion of the conductive layer, the second portion of the capping layer and the support layer.