The electrical trap properties in ultrathin oxide MOSFETs are extracted using 1/f(l) low frequency noise components of gate leakage current. The technique is based on the low frequency noise measurements which are capable of probing trap states over the energy and space. The gate voltage is swept between 0.4 and 1.32 V to obtain the different power slopes gamma of 1/f(l) noise spectrum. From the measured noise data, the trap parameters such as slow trap densities and capture cross-section are accurately determined as a function of trap energy and trap distance. The 1/f(l) noise measurement results confirm that the capture cross-sections depend strongly on the surface potential, and the slow trap densities estimated near the band edge and at the Si-SiO2 interface are higher than those near the midgap and deeper distance. Moreover, the parallel conductance spectroscopy of slow traps is reproduced by 1/f(l) low frequency noise measurements, and is verified by the low frequency plateau in measured conductance loss G(p)(f)/w. For the purpose of investigating the dependency of trap parameters on the complex admittance of oxide traps, the Cole-Cole plots for different trap profiles, a uniform and exponentially decreasing trap distribution in space, are calculated using the theoretical model. The noise spectroscopy technique further reveal the dynamic evolution of trap states and gives a clear physical understanding of the pertinent low frequency noise sources. (C) 2003 Elsevier Ltd. All rights reserved.