Highly oriented ?-Al2O3 thin films on 4H-SiC were engineered to demonstrate their potential as a crystalline high-k gate dielectric in SiC power MOSFETs. As-deposited Al2O3 thin films grown on 4H-SiC (0001) by thermal atomic layer deposition (ALD) were amorphous as determined by in-situ reflection high-energy electron diffraction (RHEED). Upon annealing in N2 at 1100°C, the film crystallized to the ?-Al2O3 phase as observed by RHEED, high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Based on Fourier transforms of the HRTEM image, an epitaxial relationship of ?-Al2O3 (111) on 4H-SiC (0001) was observed in which ?-Al2O3 (-110) is oriented with 4H-SiC (-12-10). This orientation was further confirmed by XRD analysis in which only the ?-Al2O3 (111) and (222) peaks were observed. An abrupt interface of both amorphous and crystalline Al2O3 with 4H-SiC was determined by HRTEM.