An improved approach of wet isotropic etching of silicon wafers to obtain two-level microstructures is presented. Etching behavior of silicon with nitride/oxide mask in an acid-based etchant was studied. The shape and size of the etched trench depended mostly on the mask window size. By designing a mask and etching process correctly, the desired position and depth of an individual level could be obtained with only one masking step. This technology was a significant improvement in silicon isotropic etching technology and is expected to be used widely in semiconductor devices. (C) 2004 The Electrochemical Society.