The source-drain punch-through current in off-state TDDB stress (OSS) is shown to significantly affect off-state breakdown behavior. This paper compares various OSS methodologies available in the literature and discusses how source-to-drain punch-through affects off-state breakdown and reliability. The proposed Drain-stress with Offset (DSO) OSS methodology limits punch-through to better reflect the actual field dependence of OSS breakdown for scaled tri-gate MOSFET technologies.