Abstract: Direct Current Current Voltage(DCIV) technique can extract not only the front channel interface traps but also the back channel interface traps. The concrete steps and methods is presented and is applied to measure the front channel interface and the back channel interface traps in SOI NMOSFET which is fabricated in 0.13 μm technologie. On the basis of the DCIV theory, the interface recombination current obtained can be used to fit the theoretical equation with least-squares optimization, then both the interface trap density and its equivalent energy can be acquired. The results indicate that the back channel interface trap density of SOI NMOSFET adopting SMRT-CUT technique are larger than 10¹⁰cm^-2,and the front channel interface trap density is smaller than the back channel interfaces'. The corresponding interface trap density equivalent energy is also presented.