Corundum-structured α-In2O3 was grown by mist chemical vapor deposition (CVD) on sapphire substrates with the use of α-Ga2O3 buffer layers. The use of ozone (O3) and thermal annealing in air were effective for improved surface morphology and electrical properties of the α-In2O3 layer. MOSFETs were fabricated using the α-In2O3 layer, where the residual electron concentrations were temporary reduced by doping Mg acceptors. Nevertheless the MOSFETs showed the best field-effect mobility of as high as 187 cm2/V⋅s and the best effective mobility of as high as 240 cm2/V⋅s, suggesting high potential of α-In2O3 MOSFETs.