An implantable micro-miniature device is disclosed. The device comprises athin hermetic insulating coating and at least one thin polymer or metal secondarycoating over the hermetic insulating layer in order to protect the insulatinglayer from the erosive action of body fluids or the like. In one embodiment theinsulating layer is ion beam assisted deposited (IBAD) alumina and the secondarycoating is a parylene polymer. The device may be a small electronic device suchas a silicon integrated circuit chip. The thickness of the insulating layer maybe ten microns or less and the thickness of the secondary layer may be between about0.1 and about 15 microns.
