Significant applications of scatterometry to a wide variety of diffracting structures made from semiconductor materials are reviewed. Data from investigations that have spanned more than 10 years and studied several types of scatterometers will be presented, and the salient results of these efforts summarized. As a metrology technique scatterometry is shown to be capable of measuring developed photoresist gratings, etched poly-Si gratings, film layer thickness', several types of photomask gratings, DRAM memory cell arrays and can even be used to characterize subtle profile features that may exist on these materials. As a sensor or process monitor, the technique is shown to have the ability to monitor stepper focus and exposure dose, post exposure bake time and photoresist silylation. To validate the success of these investigations, comparisons to measurements made by conventional metrologies like scanning electron microscopes (SEM), atomic force microscopes (AFM) and ellipsometers will be presented for much of the data. In all instances scatterometry measurements are shown to agree well with these other methods. Finally, some discussion on possible future applications, and the direction in which the technique is evolving, will be presented.