Abstract: In-depth distribution of carrier mobility can be obtained by measuring the gate capacitance and the transconductance of deep-depletion SOS/MOSFET in linear region as a function of gate bias voltages. The defect scattering mobility can be expressed as μ_EP=μ₀e^-αx₀, where μ₀ and α are two constants characterizing the crystalline quality and the indepth change of defect density with distance x₀ in SOS film respectively. The effect of growth technology and substrate surface quality on μ₀ and α values have been described.