The breakdown path induced by BTI stress in a MOSFET device can be traced from the experiment. It was demonstrated on advanced high-k metal gate CMOS devices. RTN traps in the dielectric layers can be labeled as a pointer to trace the breakdown path, i.e., from the leakage by measuring the Ig current as a function of time. It was found that breakdown path tends to grow from the interface of HK/IL or IL/Si which is the most defective region. Two types of breakdown paths will be presented. The soft-breakdown path is in a shape like spindle, while the hard breakdown behaves like a snake-walking path. These two breakdown paths are reflected in a two slopes TDDB lifetime plot. These new findings on the breakdown-path formation will be helpful to the understanding of the reliability in HK CMOS devices.