Forming a planar semiconductor surface

A method for producing a planar semiconductor surface, the method comprising:

• forming a workpiece that has a carrier substrate, one or more insulating layers on the carrier substrate, a semiconductor layer on the one or more insulating layers, a first etch stop layer on the semiconductor layer, and a second etch stop layer on the first etch stop layer;
• forming a contact on the workpiece;
• biasing the workpiece to a second voltage through the contact;
• etching the second etch stop layer and part of the first etch stop layer with a photo-electrochemical etching and the second voltage that selectively removes the second etch stop layer faster than the first etch stop layer;
• biasing the workpiece to a first voltage through the contact, wherein the first voltage is different than the second voltage;
• and
• etching the first etch stop layer and part of the semiconductor layer with the photo-electrochemical etching and the first voltage that selectively removes the first etch stop layer faster than the semiconductor layer to produce a semiconductor device with a planar surface on the semiconductor layer,
• wherein the first etch stop layer has a first doping type, and the second etch stop layer has a second doping type that is different than the first doping type.