We report anisotropic chemical wet etching of ͑111͒ and ͑100͒ silicon wafers using an acidic solution. The etching is performed using a solution consisting of hexafluorosilicic acid ͑H 2 SiF 6 ͒ and nitric acid. For silicon samples with ͗111͘ orientation, the etching results in the formation of crystallographic features with hexagonal openings. The walls of the crater are assumed to be different ͗111͘ planes with their crossing with ͗211͘ planes. Extended periods of etching result in the formation of scale-repeated features resembling the fractal structures. Etching of a ͗100͘ silicon was also been examined, which indicated the evolution of concave corners and ͗111͘ and ͗331͘ planes.