A method for forming a cavity in a silicon substrate, a surface of the silicon substrate having a tilting angle relative to a first plane of the silicon substrate, and the first plane being a {111} plane of the silicon substrate, and situation of an etching mask on the surface of the silicon substrate. The etching mask has a retarding structure that protrudes into the mask opening, and a first etching projection region. All further edges of the mask opening outside the first etching projection region are situated essentially parallel to {111} planes of the silicon substrate. The method includes an anisotropic etching of the silicon substrate during a defined etching duration. An etching rate in the directions of the silicon substrate is lower than in other spatial directions, and the first retarding structure is undercut in a first undercut direction going out from the first etching projection region.