The present invention provides an interconnect apparatus and a method of forming the interconnect apparatus. Two substrates, such as wafers, dies, or a wafer and a die, are bonded together. A first mask is used to form a first opening extending partially to an interconnect element formed on the first wafer. A dielectric liner is formed, and then another etch process is performed using the same mask. The etch process continues to expose interconnect elements formed on the first substrate and the second substrate. The opening is filled with a conductive material to form a conductive plug. The present invention also discloses a 3DIC interconnect apparatus and a method.