Silicon bulk micromachining using anisotropic etching has become an established method for producing micromechanical structures in silicon. Commercial applications for micromachining include pressures sensors, accelerometers, optical spectrometers, and ink jet nozzles. Typically, silicon (111) planes etch at a much slower rate than the (100) planes in certain etchants. These included potassium hydroxide (KOH), ethylene diamine pyrocatechol (EDP), sodium hydroxide (NaOH), ammonium hydroxide (NH4OH), cesium hydroxide (CsOH), tetramethyl ammonium hydroxide (TMAH), and hydrazine (N2H4). Due to its anisotropy, reported to be as high as 400:1 [(100):(111)], high etch rate (4 mum/min) and safety considerations, KOH remains the most widely used silicon anisotropic etchant. In this paper, we report the use of KOH to create silicon microstructures with vertical sidewalls on (100) wafers.