We investigate hole mobility in InSb-based ultrathin body (UTB) devices based on physical modeling. For arbitrary surface orientation, the dependence of hole mobility on body thickness and biaxial strain is evaluated. The anisotropic band structures under quantum confinement are computed by solving the six-band k.p Schrodinger and Poisson equations in a self-consistent way. Hole mobility is calculated by the Kubo-Greenwood formula. Physical models include acoustic and optical phonons, polar optical phonons, and surface roughness scattering mechanisms. Our results show that in InSb-based devices with various surface orientations, hole mobility begins to deteriorate as body thickness is reduced below a certain range. It is important that mobility improvement from non-(001) surface orientation is observed, especially for extremely thin body. With regard to biaxial strain, compressive strain is effective to enhance hole mobility for different orientations. Additionally, in both unstrained and strained cases, the optimal surface/channel direction for hole mobility is obtained along the (110)/[(1) over bar 10] direction, followed by (111)/any, (110)/[001], and (001)/any directions. (C) 2015 Elsevier Ltd. All rights reserved.