Six different configurations for metal-oxide-semiconductor field-effect-transistor reflectance microscopy are presented, each one revealing a particular contrast of the operating structure. These different images are obtained by interchanging the modulation of gate-source and drain-source potentials, as well as by varying the probe beam intensity. Three main components were identified in the signal, their relative importance depending on the experimental configuration: the electroreflectance component, the photoinjected carrier (probe-induced) component and the bias current (Joule effect) component. The high ability of the technique to detect defects in these structures is also demonstrated. ©1997 American Institute of Physics.