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This paper reports the design and fabrication of high-aspect-ratio needlelike silicon structures that can have complex geometry. The structures are hundreds of micrometers tall with submicrometer-sharp protrusions, and they are fabricated using a series of passivated and unpassivated deep reactive-ion etching (DRIE) steps. A simple model is presented to predict the geometry of the structure based on the etch mask and the etch sequence. Model predictions are in good qualitative agreement with fabrication results, making it a useful design tool. The model is compared with literature reports on tapered DRIE.