A quantitative theoretical model for bulk 1/fnoise in semiconductor resistors has been developed. The model uses the fact that random fluctuations of the steady‐state deep level trapped electron density at some point in a depletion layer decay exponentially with a time constant which depends on the local free‐electron density. The model was used to derive an exact integral expression and a simple approximate analytic expression for the spectral density of bulk 1/fand generation noise in unsaturated field‐effect transistors. Excellent agreement with experimental results is obtained. The relationship between bulk 1/fand generation noise spectra is discussed.