Ge gate-all-around fin field-effect transistors (Ge FinFETs) with a capacitive effective thickness of a few nanometers have been successfully achieved via atomic-layer-deposited (ALD) high-dielectric on and by adopting low-cost thermo ALD equipment. The MOS interface properties of the or structures have been studied systematically. It has been found that a interfacial layer that is greater than approximately 2.5 nm results in a significant degradation of the MOS interfaces, while an equivalent oxide thickness of is still possible while maintaining good interface quality. The Ge FinFET’s value has been demonstrated with the gate stack prepared using a thermal ALD layer of . The experimental results indicate that the MOS interface quality obtained with the technique developed for high-permittivity/Ge gate stacks is also extremely useful for the fabrication of triangle-fin complementary metal oxide semiconductor devices. An ratio of and a subthreshold swing of were obtained for the triangular n-type Ge gate-all-around FET with (111) sidewalls. The drain current at is .