A process for making at least one porous area (ZP) of a microelectronic structure in at least one part of an conducting active layer (6), the active layer (6) forming a front face of a stack, the stack comprising a back face (2) of conducting material and an insulating layer (4) interposed between the active layer (6) and the back face (2), said process comprising the steps of: a) making at least one contact pad (14) between the back face (2) and the active layer (6) through the insulation layer (2), b) placing the stack into an electrochemical bath, c) applying an electrical current between the back face (2) and the active layer (6) through the contact pad (14) causing porosification of an area (ZP) of the active layer (6) in the vicinity of the contact pad (14), d) forming the microelectronic structure.