This paper describes the electrochemical deoxidation of thin silica layer on silicon in molten salts. The oxide, 2μm in thickness, is formed on p-type silicon by thermal oxidation and electro-deoxidized in molten calcium chloride at 850°C. Distinctive surface architectures are obtained composed of spheres, nano-fibres and pores. The electro-deoxidized surfaces are formed, which absorb light up to 92% in the visible region of spectrum. This black silicon is attractive in many fields of application where specifically high silicon surface to volume ratio is of importance, in particular, in production of antireflection coatings in solar cells.