A wafer includes a process control monitor (PCM) structure formed on a substrate. The PCM structure includes detection and reference structures. The detection structure includes a first electrically conductive line arrangement formed in a first structural layer on the substrate and a first protection layer surrounding the first electrically conductive line arrangement. The reference structure includes a second electrically conductive line arrangement formed in the first structural layer on the substrate, a second protection layer surrounding the second electrically conductive line arrangement, an insulator material formed overlying the second electrically conductive line arrangement and the second protection layer, and a second structural layer overlying the insulator material. The insulator material does not overlie the detection structure. Methodology entails measuring a capacitance between the detection structure and the substrate, measuring another capacitance between the reference structure and substrate, and comparing the two capacitances to determine whether defects exist.