A semiconductor device includes an interconnect structure disposed over a semiconductor substrate. The interconnect structure includes a first interconnect portion and a second interconnect portion. The semiconductor device also includes a first porous dielectric portion disposed between the first interconnect portion and the second interconnect portion, and a dielectric layer surrounding the first porous dielectric portion. The semiconductor device further includes a bonding pad disposed over the dielectric layer and the first porous dielectric portion. The bonding pad and the first porous dielectric portion are separated by a first air gap.