Patent ID: 8461050

Claim:
A taper-etching method for taper-etching a layer to be etched, the layer to be etched being made of SiO 2 or SiON and having a top surface, the taper-etching method comprising the steps of: forming a separate etching mask on the top surface of the layer to be etched, the etching mask having an opening; and taper-etching a portion of the layer to be etched, the portion being exposed from the opening, by reactive ion etching so that a groove having two wall faces that intersect at a predetermined angle is formed in the layer to be etched, wherein: the etching mask is formed of a material containing elemental Al; the step of taper-etching employs an etching gas that contains a main component gas and N 2 , the main component gas contributing to the etching of the layer to be etched; and in the step of taper-etching, the elemental Al contained in the etching mask and N 2 contained in the etching gas produce a reaction product AlN, and the reaction product AlN forms a sidewall protective film serving to accomplish the taper-etching of the layer to be etched.