Abstract: A surface or surfaces of a semiconductor substrate are roughened by etching the substrate with an etchant containing (i) hydrofluoric acid, ammonium fluoride and/or acid ammonium fluoride, (ii) at least one manganese- or chromium-containing oxidizing agent, such as potassium permanganate, potassium manganate, chromium trioxide, potassium or sodium chromate and potassium or sodium dichromate, and (iii) an alkali. If a rougher surface or surfaces are desired, the substrate is pre-etched with an etchant containing (i) the fluorine-containing compound and (ii) the manganese-containing oxidizing agent, and then, etched with the above-mentioned etchant.