In this paper, the evolution of BTI induced leakage paths has been evaluated by Ig-RTN technique and demonstrated on HK/MG CMOS devices. First, RTN measurement has been elaborated to identify the location of traps and their correlation to the leakage current. Then, the measured gate current transient can be used to analyze the formation of breakdown path. The results show that the evolution of leakage paths can be divided into three stages, i.e., (1) the early stage-only gate leakage and discrete RTN traps are observed, (2) the middle stage - the traps interacting with the percolation paths and exhibits a multi-level current-variation, and (3) the last stage - the formation of breakdown path. These findings provide useful information on the understanding of gate dielectric breakdown in high-k CMOS devices.