Inversion and accumulation-layer electron mobility in n-channel 4H-SiC MOSFETs have been investigated using Hall measurements. In the inversion-mode MOSFETs, Hall mobilities of similar to 70-80 cm(2)/V-s were obtained compared to a field-effect mobility (mu(FE)) of similar to 5 cm(2)/V-s. Accumulation-layer electron mobilities (mu(acc)) of similar to 350 cm(2)/V-s and 200 cm(2)/V-s were extracted on samples with different channel doping concentrations. In contrast, the field-effect mobility under accumulation was similar to 2-3 cm(2)/V-s.