Miniature mounting grooved substrate

A miniature mounting device on which elements such as optical fibres 100 can be accurately held comprises a substrate 1 having a micromachined groove 2 having an enlarged opening for receiving the element and an overlayer 3 extending at least partially over the groove. The groove may be formed by anisotropic etching. The substrate 1 may be silicon and the overlayer 3 silicon nitride. Pre-stressed lips 3b of e.g. chromium may be formed in a stressed metal layer on the overlayer. The groove and overlayer may be on different substrates.