Electron thermal waves originated owing to absorption of modulation laser beam are studied in submicron unipolar semiconductor films. We assume that the film's thickness is much less than the electron cooling length. Thanks to this assumption the thermal waves propagate only in the electron gas, and there are absent in the phonon subsystem. General boundary conditions are obtained for a heat diffusion equation taking into account both the electron surface thermal conductivity and the electron surface heat capacity. The concept of the electron surface heat capacity is introduced for the first time. Complex thermoelectric response to the electron thermal waves is analyzed. (C) 2002 Elsevier Science B.V. All rights reserved.