A single crystal silicon lens for a scanning acoustic microscope (SAM) has been developed by using lithography and chemical etching. Excellent sphericity and the minimal surface roughness demanded for a lens profile have been obtained through suitable etching. The optimum etchant conditions are with hydrofluoric, nitric, and acetic acids in the ratio of 2:3:3 at 50 degrees C. A silicon lens designed specifically for a frequency of 600 MHz has been successfully achieved with a resolution 1.8 microns expected from the wavelength. The influence of the aperture diameter of the etching mask and etching time on the concave profile was clarified. The etched concave profile for a 1 GHz range lens showed a maximum deviation from a perfect sphere of less than 0.2 microns. >