2-inch sapphire-based aluminum nitride templates with different thickness of 200 nm, 400 nm and 800 nm were fabricated by DC reactive magnetron sputtering and high temperature annealing. The characterization results of AlN templates with different thicknesses before and after high-temperature annealing were compared. The results show that the quality of AlN templates with a thickness of 200 nm fabricated by DC magnetron sputtering were significantly improved after high-temperature annealing: the full widths at half maximum (FWHM) of the rocking curves measured by high-resolution X-ray diffraction(HRXRD) before and after high-temperature annealing for (0002) were 632-658 arcsec and 70.9-84.5 arcsec respectively, while the ones before and after high-temperature annealing for (10-12) were 2 580-2 734 arcsec and 273.6-341.6 arcsec, respectively. The root mean square roughness of a 5 μm×5 μm surface area is less than 1 nm. The absorption coefficient revealed by optical transmission spectra in the UV range 260-280 nm is 14-20 cm-1. The FWHM of E2(high) phonon mode evaluated by Raman spectra decrease from 13.5 cm-1to 5.2 cm-1 and the peak shifts from 656.6 cm-1 to 657.6 cm-1, which indicate that the tensile stress in AlN templates is relaxed and became stress-free after high-temperature annealing.