A method includes: forming a transistor gate over a first substrate and at least one first dummy structure within the first substrate; forming an interlayer dielectric (ILD) layer over the gate transistor, the ILD layer including at least one contact structure formed therein and making electrical contact with the transistor gate and at least one first conductive structure formed therethrough at least partially over a surface of the dummy structure; forming a passivation layer over the ILD layer, the passivation layer comprising at least one first pad structure formed therein and making electrical contact with the conductive structure; bonding the first substrate with a second substrate; removing at least a portion of the first dummy structure, thereby forming a first opening; and forming a conductive material within the first opening for formation of a second conductive structure, the second conductive structure being electrically coupled to the first conductive structure.