A process for manufacturing an integrated device includes the steps of: providing a silicon substrate on which a silicon dioxide structure is arranged and forming a trench having first and second essentially vertical walls relative to the substrate in the structure by means of anisotropic-type etching. A concavity having a sloped wall relative to the substrate is formed by isotropic-type etching which removes the second wall so that the concavity is open to the trench and the sloped wall faces the first wall.