The potential of using low-frequency noise as a diagnostic tool for semiconductor material and device characterization is reviewed. First a brief introduction is given related to the different noise sources in order to obtain insight into the spectral information present in their response signal. Special attention is given to 1/f noise, random telegraph signal noise, and generation-recombination noise. The physics associated with the noise properties of bulk and interface defect centers is investigated and illustrated by some case studies for both metal oxide semiconductor and bipolar devices. Advantages and disadvantages compared to other spectroscopic techniques are addressed in view of future trends in electronic devices.