To provide a method and an apparatus for etching silicon and an etched silicon body manufactured by the method and the apparatus capable of easily forming a desired taper angle and achieving also the smoothing of the taper surface while no overhang shape is formed.

The pressure within a reaction chamber 1 is reduced, and a process gas (a gas mixture of SF6, C4F8 and O2) is introduced into a plasma generation chamber 2a through a gas feed pipe 4. The plasma of the process gas is generated in the plasma generation chamber 2a by applying an alternating current voltage to a coil 3, and by applying the alternating current voltage to a substrate electrode 11 at the same time, the generated plasma is drawn into the reaction chamber 2b. A sample 20 mounted to a platen 6 (silicon material formed with an etching mask) is etched into a tapered shape by the plasma drawn into the reaction chamber. An area of the silicon material that contacts with the etching mask after the etching is smaller than that of the etching mask.