A roughened silicon surface is formed by a process including repetitively performed roughening cycles. Each roughening cycles including a step for depositing a non-planar polymeric layer over an area of a silicon body and a step for plasma etching the polymeric layer and the area of the silicon body etch in a non-unidirectional way. As a result, a surface portion of the silicon body is removed, in a non-uniform way, to a depth not greater than 10 nm.