[en] Clean interface and low contact resistance are crucial requirements in two-dimensional (2D) materials to preserve their intrinsic carrier mobility. However, atomically thin 2D materials are sensitive to undesired Coulomb scatterers such as surface/interface adsorbates, metal-to-semiconductor Schottky barrier (SB), and ionic charges in the gate oxides, which often limits the understanding of the charge scattering mechanism in 2D electronic systems. Here, we present the effects of hafnium dioxide (HfO₂) high-κ passivation and SB height on the low-frequency (LF) noise characteristics of multilayer molybdenum ditelluride (MoTe₂) transistors. The passivated HfO₂ passivation layer significantly suppresses the surface reaction and enhances dielectric screening effect, resulting in an excess electron n-doping, zero hysteresis, and substantial improvement in carrier mobility. After the high-κ HfO₂ passivation, the obtained LF noise data appropriately demonstrates the transition of the Coulomb scattering mechanism from the SB contact to the channel, revealing the significant SB noise contribution to the 1/f noise. The substantial excess LF noise in the subthreshold regime is mainly attributed to the excess metal-to-MoTe₂ SB noise and is fully eliminated at the high drain bias regime. This study provides a clear insight into the origin of electronic signal perturbation in 2D electronic systems. (paper)