The low-frequency (LF) noise performance of n- and p-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with different Hf-based gate oxides, deposited by metallorganic chemical vapor deposition (MOCVD) on the same interfacial oxide layer and using polysilicon (poly-Si) as a gate material has been investigated. Independent of the gate oxide, the LF noise spectra of n- and p-MOSFETs are predominantly of the 1/f (gamma) type, with the frequency exponent gamma close to 1. For nMOSFETs, the noise spectral density of HfO2 devices is two orders of magnitude higher than for SiON or HfxSi1-xON (silicates), where 0 < x < 100%, most likely due to trapping by defects in the high-k layer. For the silicates with different x, no significant differences are noticed for n- and p-MOSFETs. It is shown that the noise characteristics behave as can be expected for a number fluctuations mechanism. The extracted volume and surface trap densities are significantly higher for pure HfO2 than for the HfxSi1-xON devices. In the latter case, trap densities comparable with the values for the SiON reference transistors are obtained. Hooge's parameter alpha(H), as an alternative figure of merit, shows that the devices with MOCVD HfO2 gate dielectric have the noisiest performance, while HfxSi1-xON MOSFETs yield the lowest alpha(H), even better than for SiON.