The integrity of doping in transistor structures was diagnosed using scanning nonlinear dielectric microscopy (SNDM). Nonlinear capacitance profiling and pinpoint capacitance-voltage analysis were done through SNDM, and the results clearly discriminated between a depletion layer and a tailing of carrier distribution due to outdiffusion of dopants in an n(+)/p junction. This analysis was applied to n(+)/p/n(+) and p(+)/n/p(+) transistor channel structures formed with different process parameters. An increase in the n(+) activation temperature from 800 to 950 degrees C caused a narrowing of the p-type region in the n(+)/p/n(+) structure. A decrease in the substrate doping concentration from 2 X 10(18) to 2 X 10(17) cm(-3) caused a depletion of the entire channel when the gate length was less than 200 rim. The influence of channel depletion was proven to be more severe in p(+)/n/p(+) transistor channel structures because boron had higher diffusivity than, arsenic. (c) 2006 American Vacuum Society.