Recently, we have shown the possibility to form Zn nanoparticles in ZnO crystal using Nd:YAG laser radiation. The aim of this work is to elaborate technology of nanoparticles formation in metal oxide semiconductors by laser radiation. The experiments were performed on hydrothermally grown n-type ZnO single crystals with size 5.0x5.0x2.0 mm. The ZnO crystals were irradiated by the fourth harmonic of pulsed Nd:YAG laser with the following parameters: wavelength λ = 266 nm, pulse duration τ = 3 ns and laser intensity up to Imax = 315 MW/cm2. Nanostructural features of the samples were studied by field emission scanning electron microscope (FESEM) and Raman spectroscopy. Topography measurements and electrical conductivity mapping were performed by atomic force microscope (AFM). It was found that the formation of Zn nanoparticles characterizes by two thresholds intensities: the first threshold intensity Ith1 = 3.5 MW/cm2 at which conductivity starts to increase monotonously up to 103 times, till the second threshold intensity Ith2= 290.0 MW/cm2, due to the increase of the Zn interstitials (Zni) concentration at the surface of the ZnO sample. Second stage of the process is “black ZnO” appearance at the irradiated surface. This phenomenon is caused by the agglomeration of Zni in nanoparticles wihich the diameter increase with number of laser pulses. An evidence of Zn phase formation in ZnO crystal is appearance of 70 cm-1 band in Raman spectra after irradiation by the laser. The work was supported by Latvian National Research Programme in Materials Science (IMIS2) (2014-2017).