Abstract: The high dielectric constant (high-κ) materials of hafnium oxide (HfO2) and aluminum oxide (Al₂O₃) were grown by atomic layer deposition (ALD) and investigated for integration as gate dielectrics in silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors (MOSFETs). Smooth HfO₂ films were grown on 4H-SiC at temperatures of 200-300°C at a deposition rate of 1-2 Å/cycle. A temperature-dependent phase transition from amorphous layer-by-layer growth to polycrystalline three-dimensional island growth was observed by in-situ reflection high-energy electron diffraction (RHEED) and atomic force microscopy (AFM). No interfacial layer formation was observed by in-situ X-ray photoelectron spectroscopy (XPS) and an abrupt interface was confirmed by high-resolution transmission electron microscopy (HRTEM). An asymmetric band alignment at the HfO₂/4H-SiC interface was determined by XPS and supported by density functional theory calculations. As a result, a high leakage current density of 10-3 A/cm2 at 3 MV/cm was observed in MOS capacitors. Al₂O₃ was studied due to its larger bandgap and potential to form a crystalline oxide film. Epitaxial γ-Al₂O ₃ thin films were engineered by post-deposition rapid thermal annealing of amorphous Al₂O₃ films grown by ALD. An epitaxial relationship of γ-Al₂O₃ (111) || 4H-SiC (0001) and γ-Al₂O₃ (44¯0) || 4H-SiC (112¯0) was determined by selected area electron diffraction and synchrotron X-ray scattering. An abrupt crystalline interface was observed by HRTEM in films up to 200 Å thick. The in-plane alignment between the film and the substrate was nearly complete for γ-Al₂O₃ films up to 115 Å in thickness, but quickly diminished in thicker films. Mixed amorphous and polycrystalline regions were observed in Al₂O₃ films thicker than 225 Å, and negligible crystallization was observed in films thicker than 500 Å. Twinning around the [111] axis was observed in all of the films. Larger barrier heights were determined for the Al₂O ₃/4H-SiC interface compared to the HfO₂/4H-SiC interface and as a result, low leakage current of 10-3 A/cm2 was measured for amorphous Al₂O₃ films up to an electric field of 8 MV/cm. This state-of-the-art electric field strength is promising for the integration of these materials in SiC power MOSFETs. However, higher leakage current was measured for crystalline Al₂O₃ films due to conduction along the twin boundaries. Further work is proposed to optimize the quality of the epitaxial Al₂O₃ films for these applications.