Thin films of aluminum nitride (AlN) have been grown on semiconductor Si (100) substrates using the pulsed laser deposition method. The laser-deposition parameters and substrate temperature play an important role in fabricating high-quality AlN films. The films deposited at higher temperatures have shown better crystalline properties and also are highly oriented perpendicular to the substrate. The films have been characterized using X-ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopic techniques. An atomic force microscope was used to obtain three-dimensional topographs of the surfaces of these films. These maps are useful both for quantitatively characterizing the roughness of the surfaces and for gaining information about the basic mechanisms involved in the film growth process. The hardness as a function of the penetration depth has been measured using the nano-indentation method.