A substrate includes first and second semiconductor layers doped with opposite conductivity type in contact with each other at a PN junction to form a junction diode. At least one through silicon via structure, formed by a conductive region surrounded laterally by an insulating layer, extends completely through the first semiconductor layer and partially through the second semiconductor layer with a back end embedded in, and in physical and electrical contact with, the second semiconductor layer. A first electrical connection is made to the first through silicon via structure and a second electrical connection is made to the first semiconductor layer. A testing current is applied to and sensed at the first and second electrical connections in order to detect a defect in the at least one through silicon via structure.