the layer the polysilicon is then patterned 58 in order to provide holes for etching the sacrificial layer thus the layers for the fixed mirror have been produced a sacrificial layer for forming a fabry perot cavity is deposited by lpcvd sio 2 deposition 59 it is not necessary to pattern the sacrificial layer next the layers for the movable mirror are produced a layer of polycrystalline silicon is deposited 80 and conductive area is formed by ion implantation 81 the layer is patterned 82 in order to provide holes for etching the sacrificial layer next a further sacrificial layer is made with lpcvd sio 2 deposition 83 and the layer is patterned 84 with this patterning locations of anchors are determined for the movable mirror the density of the anchors is preferably larger in the optical area than in the surrounding area this way a higher value of stiffness is achieved in the optical area compared to the surrounding area a layer of polycrystalline silicon is then formed with lpcvd deposition 85 and holes are etched 86 thus the layers for the movable mirror have been produced metallization with aluminium is performed for the connectors by sputtering and patterning.