The methods of optical and scanning electron microscopy (SEM) along with electronic probe X-ray spectral microanalysis proved an opportunity to manipulate by means of laser irradiation with clusters, structural impurity defects and nanoaggregates in a space charge region (SCR) of a semiconductor in devices with a Schottky barrier formed on the basis of silicon and chalcogenide semiconductors. The optimal conditions of intensity of the millisecond laser irradiation at which the sizes of clusters diminish considerably are established, as well as the densities of edge dislocations in SCR and of dot defects. The dependences of the surface states density on contact, of the density of the deep levels in SCR and transition nanosize layer on a metal-semiconductor contact on the conditions of a laser exposure are studied. The presence of both the 5/500 nm deep transition structured layer and the modulated band gap causes the occurrence of tunnel-resonance charge transfer in contacts with a Schottky barrier, which can result in the appearance of sites with negative differential resistance in a current-voltage characteristic of the investigated structures. (c) 2005 Elsevier B.V All rights reserved.