Circular metal-oxide-semiconductor field-effect transistors (MOSFETs) with various gate dimensions are fabricated on 4°off-axis and regular (100) silicon substrates. The influences of substrate orientation, gate length and width on the dc performance of the MOSFETs are investigated and the underlying mechanism is discussed. The on/off ratio, threshold voltage, field effect mobility, transconductance and drain current are compared and the differences can be explained by the interface state density and the surface roughness scattering. The results provide guidelines for the optimization and reliability of the MOSFETs on the off-axis silicon wafers.