For the first time, the breakdown path induced by BTI stress can be traced from the RTN measurement. 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. 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 are revealed. The soft-breakdown path is in a shape like spindle, while the hard breakdown is 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.