A method of fabricating a semiconductor device includes providing a semiconductor substrate having a first surface and a second surface opposite the first surface, forming an alignment key and a connection contact that penetrate a portion of the semiconductor substrate and extend from the first surface toward the second surface, forming a first circuit on the first surface of the semiconductor substrate such that the first circuit is electrically connected to the connection contact, recessing the second surface of the semiconductor substrate to form a third surface exposing the alignment key and the connection contact, and forming a second circuit on the third surface of the semiconductor substrate such that the second circuit is electrically connected to the connection contact.