Random telegraph noise (RTN) in gate-induced drain leakage (GIDL) and gate edge direct tunneling (EDT) leakage currents under GIDL bias conditions were characterized in MOSFETs with a high- k gate dielectric for the first time. The RTNs were analyzed through systematic measurement and calculation. The results indicate that a high-current state in a GIDL current can be attributed to electron capture due to thermal emission. However, electron emission from a trap was mainly affected by gate bias. Both capture and emission times in the RTN of the EDT current had gate bias dependence. Moreover, multilevel RTN waveforms were detected in a device, and our analysis indicated that the multilevel RTN is the result of the combination of the RTNs of the GIDL and EDT currents. The analysis also indicated that two independent traps in the high- k gate dielectric can produce a four-level RTN in the GIDL current. This paper provides the fundamental physics required to understand such leakages in nanoscale MOSFETs and devices that utilize band-to-band tunneling.