The invention relates to a micro-device with a cavity (50), the micro-device comprising a substrate (10, 110), the method comprising steps of: A) providing the substrate (10, 110), having a surface and comprising a sacrificial
oxide region (20, 107, 115) at the surface ( ); B) covering the sacrificial
oxide region (20, 107, 115) with a
porous layer (40, 114, 124) being permeable to a vapor HF etchant (100), and C) selectively
etching the sacrificial
oxide region (20, 107, 115) through the
porous layer (40, 114, 124) using the vapor HF etchant (100) to obtain the cavity (50). This method may be used in the manufacture of various micro-devices with a cavity (50), i.e. MEMS devices, and in particular in the encapsulation part thereof, and
semiconductor devices, and in particular the BEOL-part thereof.