A novel FinFET structure with body spacers in sub fin (BSSF) is proposed to improve the fin height variation produced in the manufacturing processes. Device simulation results are presented to show the electrical variations improvement. The effective fin height (H-eff) of FinFETs with BSSF is well controlled because it only depends on the silicon epi layer thickness (T-Si). Taking advantage of the precisely controlled epitaxy process, H-eff uniformity of FinFETs with BSSF is much better than conventional bulk FinFETs. Benefit from the smaller H-eff variation, FinFETs with BSSF show much smaller electrical characteristics variation. For n-FinFETs, the I-on variation improves from 33.46% for conventional bulk FinFETs to 8.05% for FinFETs with BSSF. Additionally, manufacturing of FinFETs with BSSF is compatible with that of the state-of-the-art bulk FinFETs, promising for its applications in massive production. (C) 2016 Elsevier Ltd. All rights reserved.