The correlation deep level transient spectroscopy (DLTS) method is developed for insulator/semiconductor interface studies. Trap transient modeling indicates that the energy range in which the trap transients can contribute to the DLTS signals of the correlation method is about 12 kT, and is much wider than that of the boxcar method (several kT). Moreover, large voltage pulse for saturation will cause the capacitance transient to shift away from the ideal exponential due to the sum of the various emission rates. Hence, the equations for determination of interface trap density suitable for the boxcar method is invalid for the correlation method. For this reason, an equation for determining the interface trap density suitable for the correlation method is derived. The interface trap density determined by this method agrees well with other methods.