As semiconductor geometries decrease, the size of a defect that leads to circuit failure also decreases. While many defects will cause photoemission or observable leakage paths, occasionally a defect will occur in an area that cannot be easily analyzed. In this analysis, a yield issue in nickel-silicide (NiSi) piping is investigated. The failure had characteristics that fell into areas that avoided detection. A planar transmission electron microscope of the substrate at the defect site was performed to look for evidence of crystalline defects that would allow a conduction path across the channel. This analysis found that NiSi encroachment was the root cause of the yield issue. All analyzed units had the defect between stacked nFET transistors. Because the defect was between stacked nFET gates, the results show that the failure characterization required control of multiple gates to measure the transistor off-state drain to source current.