Method for electrolytically etching semiconductor material

An electrolytic etching method for semiconductor material structure having more than one type of semiconductor material conductivity therein, said method comprising:

• providing a semiconductor material structure having a first region of a first conductivity type, except in selected regions thereof, which is in a substantially crystalline relationship with a second region of a second conductivity type, said first region being in two strata of two different conductivities, a first strata of a lower conductivity which adjoins said second region and a second strata of a relatively higher conductivity which adjoins said first strata without adjoining said second region, said second strata having one or more said selected regions contained completely therein which are of said second conductivity type,
• providing a metal etching mask on said second region, and
• etching electrolytically said semiconductor material structure by electrically contacting said metal etching mask and placing said semiconductor material structure as masked and contacted in an electrolyte bath.