The dielectric performance and charge trapping properties of $ \hbox{HfO}_{2}$ on a Ge substrate with various passivating interfacial layers (PILs), such as $\hbox{SiO}_{x}\hbox{N}_{y}$ , $\hbox{AlO}_{x}\hbox{N}_{y}$ , $\hbox{HfO}_{x}\hbox{N}_{y}$ , and $\hbox{LaO}_{x}\hbox{N}_{y}$ , are investigated. The large capacitance–voltage ( $C$ – $V$ ) hysteresis of $ \hbox{HfO}_{2}$ on a Ge substrate ( $\sim$ 1500 mV) was not improved by inserting either $\hbox{HfO}_{x}\hbox{N}_{y}$ or $\hbox{LaO}_{x}\hbox{N}_{y}$ PIL between the $\hbox{HfO}_{2}$ and Ge substrates, while both $\hbox{SiO}_{x}\hbox{N}_{y}$ and $\hbox{AlO}_{x}\hbox{N}_{y}$ PILs induced a noticeable reduction of $C$ – $V$ hysteresis. As the PILs' thicknesses increased, the $C$ – $V$ hysteresis of $ \hbox{HfO}_{2}$ with $\hbox{SiO}_{x}\hbox{N}_{y}$ PIL decreased to almost zero, while that of $\hbox{HfO}_{2}$ with $\hbox{AlO}_{x}\hbox{N}_{y}$ PIL decreased but was saturated at approximately 400 mV. Furthermore, the charge trapping property of $ \hbox{HfO}_{2}$ with $\hbox{SiO}_{x}\hbox{N}_{y}$ PIL on a Ge substrate is comparable to that of $\hbox{HfO}_{2}$ grown on a Si substrate. Negligible $C$ – $V$ hysteresis and negligible charge trapping of $\hbox{HfO}_{2}$ with $ \hbox{SiO}_{x}\hbox{N}_{y}$ PIL were understood from the fact that $\hbox{SiO}_{x}\hbox{N}_{y}$ is more resistant to react with a Ge substrate and defective Ge suboxides are efficiently suppressed during the formation of $\hbox{SiO}_{x} \hbox{N}_{y}$ PIL and $\hbox{HfO}_{2}$ layers.