An etching technique used to produce a very precise edge in a silicon crystal. The technique is used to produce mesa layers or during the manufacture of VMOS circuits.

A silicon crystal with (100) orientation is etched from the surface by a suitable etch, such as potassium hydroxide, that will not etch perpendicularly to the (111) plane. The etching process therefore follows the direction of the (111) crystal planes and stops at any point where the (111) planes intersect. This results in a very precise V-groove in the material. The depth of the groove depends on the size of the original opening in the surface oxide layer and etching to a precise predetermined depth is therefore possible with this technique.