Preparation of heteroepitaxial Pb(Mg1/3Nb2/3)O-3 (PMN) thin films by pulsed laser deposition (PLD) was successful on Si(001) substrate using La0.5Sr0.5CoO3 (LSCO)/CeO2/YSZ triple buffer structure for the first time. Using this triple buffer, the formation of pyrochlore type compounds was completely suppressed. The heteroepitaxial growth of PMN, LSCO, CeO2 and YSZ on Si(001) substrate was confirmed by both X-ray pole figure measurement and RHEED observation. In this work, the thickness dependency of both crystal structure and electrical properties of PMN thin film was examined as a function of the thickness of PMN between 1.6 and 130 Mm. The lattice parameter and FWHM (omega scan) of PMN thin films increased with the decrease of the thickness of PMN. The current density of PMN thin film was low irrespective of the thickness of PMN (9.2 x 10(-7) and 2.9 x 10(-6) A/cm(2) for 130- and 6.3-nm-thick, respectively Dielectric constant of heteroepitaxial PMN thin film was decreased with the thickness, which was attributed to the depletion width.