Semiconductor device with air gap and method for preparing the same

A method for preparing a semiconductor device, comprising:

• forming an interconnect structure over a semiconductor substrate, wherein the interconnect structure comprises a first interconnect portion and a second interconnect portion;
• forming a dielectric layer over the semiconductor substrate and covering the interconnect structure;
• forming a first opening penetrating through the dielectric layer, wherein the first opening is between the first interconnect portion and the second interconnect portion of the interconnect structure;
• filling the first opening with a first porous dielectric portion;
• forming a bonding pad over the dielectric layer and the first porous dielectric portion;
• and
• performing a heat treatment process to form a first air gap between the first porous dielectric portion and the bonding pad.