In this study, thin films of Ef(2)O(3) are deposited by low-pressure metal-organic chemical vapor deposition (MOCVD) using a tris(isopropylcyclopentadienyl)erbium precursor and 02 on various substrates, including p-type Si(100), Si(111), Corning glass, and c-axis-oriented alpha-Al2O3(0001). The resulting films are extensively characterized in order to demonstrate their applicability as antireflective and protective coatings and as high-k gate dielectrics. The interplay existing among the substrate, the nucleation kinetics, and the resulting structural, morphological, optical, and electrical properties of Er2O3 thin films is explored. Fast nucleation governed by surface energy minimization characterizes the growth of (111)-oriented Er2O3 on Si(100), glass, and alpha-Al2O3. Conversely, nonhomogeneous nucleation leads to polycrystalline Er2O3 on Si(111) substrates. Er2O3 films grown on Si(100) possess superior characteristics. A high refractive index of 2.1 at 589.3 nm, comparable to the value for bulk single crystalline Er2O3, a high transparency in the near UV-vis range, and an optical bandgap of 6.5 eV make Er2O3 interesting as an antireflective and protective coating. A static dielectric constant of 12-13 and a density of interface traps as low as 4.2 x 10(10) cm(2) eV(-1) for 5-10 nm thick Er2O3 layers grown on Si(100) render the present Er2O3 films interesting also as high-k dielectrics in complementary metal oxide semiconductor (CMOS) devices.