The influence of process induced defects on the surface quality of wet anisotropically etched cavities in silicon wafers is investigated. Localized thinning of silicon substrates using cavities of this kind is a common method for fabricating, e.g., diaphragms for silicon pressure sensors. Wafers with four different concentrations of interstitial oxygen varying from 6.0 X 10(17) cm(-3) to 9.3 X 10(17) cm(-3) were exposed to a thermally simulated complementary metal oxide semiconductor process and subsequently anisotropically etched with potassium hydroxide or tetramethylammonium hydroxide solution. Crystal defects caused by oxygen precipitation, such as stacking faults, punching systems, and dislocations, were found to be the origin of large craterlike defects in the sidewalls of the cavities. Wafer material with an initial concentration of interstitial oxygen between 6.0 x 10(17) cm(-3) and 6.9 x 10(17) cm(-3) exhibits a very low density of small precipitate-dislocation complexes and, thus, etched cavities of good surface quality are obtained. In wafers with interstitial oxygen concentrations higher than 7.8 x 1017 cm-3 bulk stacking faults were observed and the surface quality of the cavity sidewalls diminishes. The microscopic morphology of the craterlike defects in the {111} sidewalls of the etched cavities is explained using a computer simulation of the etching process. An influence of process induced defects on the surface quality of wet anisotropically etched {100) surfaces was not found.