In this study we report on structural and electric properties of ?-Ga2O3 on Si and GaN substrates. Since Ga2O3 has a band-gap of 4.8 eV at room temperature and a dielectric constant of 10.2~14.2, Ga2O3 can be a potential candidate dielectrics for MIS devices. ?-Ga2O3 has been deposited using various techniques such as radio-frequency sputtering, plasma enhanced atomic layer deposition (PEALD), and pulsed laser deposition (PLD). In particular, epitaxial Ga2O3 thin films grown on n-GaN/Al2O3 substrate by PLD technique have a monoclinc ?-Ga2O3 phase and peaks were indexed as (-2 0 1) and higher order diffractions. Optical transmittance of the epitaxial ?-Ga2O3 film was more than 90% from UV to visible spectral regions and the optical band-gap of the ?-Ga2O3 was calculated to be about 4.8 eV. Moreover, we have fabricated MFIS capacitors using Ga2O3 and Ba0.5Sr0.5TiO3 (BST) thin films on GaN/Al2O3 substrate by pulsed laser deposition. The epitaxial growth, structural analysis, and dielectric properties of the Ga2O3 films and BST thin films will be discussed.