Dry etching method, semiconductor element manufacturing method, and cleaning method

Provided is a dry etching method with which it is possible to selectively etch an object to be etched, which contains lanthanum, at a sufficient etching rate compared to an object not to be etched without using plasma. A dry etching method is provided with a dry etching step in which an etching gas containing nitrosyl fluoride is brought into contact with a member (12) to be etched having an object to be etched and an object not to be etched, and the object to be etched is selectively etched compared to the object not to be etched without using plasma. The object to be etched is the object to be etched by the etching gas, and the object to be non-etched is not the object to be etched by the etching gas. The object to be etched contains lanthanum. 提供能够不使用等离子体而与非蚀刻对象物相比选择性地且以充分的蚀刻速度蚀刻含有镧的蚀刻对象物的干式蚀刻方法。一种干式蚀刻方法，具备干式蚀刻工序，在干式蚀刻工序中，使含有亚硝酰氟的蚀刻气体与具有蚀刻对象物和非蚀刻对象物的被蚀刻构件(12)接触，不使用等离子体而与非蚀刻对象物相比选择性地蚀刻蚀刻对象物，蚀刻对象物是蚀刻气体的蚀刻对象，非蚀刻对象物不是蚀刻气体的蚀刻对象。蚀刻对象物含有镧。