Quantum confinement effects on hole mobility in silicon and germanium double gate p-channel metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒ are studied by using a Monte Carlo method. Uniaxial stress and channel/substrate orientation effects are considered. Our result shows that the hole mobility in a ͑100͒/͓110͔ silicon well decreases with a decreasing well thickness, which is in agreement with the experimental result. The hole mobility in a germanium channel MOSFET, however, exhibits a peak in a sub-20 nm well because of the interplay between intrasubband and intersubband scatterings.Double-gate ͑DG͒ metal-oxide-semiconductor fieldeffect transistors ͑MOSFETs͒ and fin field-effect transistor have been considered as promising alternatives to bulk MOSFETs in 22 nm technology node and beyond 1-3 due to their immunity to short channel effects. Recently, advanced channel materials with higher carrier mobility than bulk Si, such as Ge ͑Ref. 4͒ and III-V materials, 5 have attracted much attention. Experimental works have shown the possibility that the inversion carrier mobility can be further improved in quantum structure MOSFETs by a subband modulation. 6,7 However, there has been little work on Ge-channel DGpMOSFETs addressing valence subband and substrate/ channel orientation effects on hole mobility.In this paper, we analyze quantum confinement effects on hole mobility as a function of a body thickness in Si-and Ge-channel DG-pMOSFETs. The low-field hole mobility is calculated by a Monte Carlo method. 8 The impact of substrate orientation on hole mobility is also evaluated. Furthermore, the effect of uniaxial compressive stress is discussed.Instead of the effective-mass approximation, the valence subband structures for two-dimensional holes in Si-and Gechannel DG-pMOSFETs are calculated self-consistently from the coupled Poisson and Schrödinger equations with a six-band Luttinger-Kohn Hamiltonian including spin-orbit coupling. 9 The Bir-Pikus deformation potentials 10 are also included to take into account the stress effect. In addition, an appropriate rotation matrix is employed when dealing with substrate orientations other than the ͑100͒ direction. 11,12 Material parameters, including Luttinger parameters, deformation potentials, and elastic constants used in the simulation, are given in Refs. 13-15. Relevant scattering mechanisms, including acoustic phonon scattering, optical phonon scattering, and surface roughness scattering, are considered in the Monte Carlo simulation. [16][17][18][19] The scattering parameters of Si and Ge are calibrated from a conventional Si MOSFET and from a SiGe-on-insulator device, respectively. 18 Figure 1 compares the hole mobility as a function of a body thickness in ͑100͒/͓110͔ Si-and Ge-channel DGpMOSFETs, where ͑͒ and ͓͔ are the notations of substrate orientation and channel direction, respectively. The choice of the ͓110͔ channel in Si is because it has a larger stress effect. The inversion hole density, p inv , is set to be 4 ϫ 10 12 cm −2 . The simulated hole mobi...