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0.39-nm ultrathin EOT ZrO 2 having κ value as high as ∼43 without an interfacial layer (IL) is demonstrated on Ge substrates. The EOT and gate leakage are much lower than the recent reported data [1]. In situ NH 3 /H 2 remote plasma treatment (RPT) after RTO-grown ultrathin ( 2 /Ge and prior to PEALD ZrO 2 leads to the formation of tetragonal phase ZrO 2 and the inhibition of GeO x IL regrowth. As the number of RPT cycles increases, it is observed that not only higher [N] but more GeO 2 component formed on Ge surface. GeO diffuses into ZrO 2 layer via the interface reaction (Ge+GeO 2 → 2GeO) and stabilize the tetragonal phase ZrO 2 . The gate dielectric has a leakage current ∼104X lower than other reported dielectrics in this EOT region. Ge (001) pMOSFET has low SS of 85 mV/dec and high I on /I off of ∼6×105 at V d = −1V, while nMOSFET has SS of 90 mV/dec and I on /I off of ∼1×105 at V d =1V. The peak electron mobility is determined by the remote phonon scattering stemming from the high-κ value. The biaxial tensile strain of ∼0.04% applied on Ge (111) nMOSFET with an EOT=0.78nm produces a 4.8% drain current enhancement along the channel.