Abstract: A reactor for applying reactive ion etching to a component, wherein a substrate holder (3) and clamping means (10) are provided for respectively supporting and securing components (8) to be exposed to reactive ion flux, that includes a separate shield arrangement (20) fixed in a detachable way on said substrate holder (3), above said clamping means (10) to mask said clamping means with respect to said reactive ion flux. Said shield arrangement (20), made up of a single ring can be mounted on said substrate holder (3) directly upon said clamping means or can also be mounted just above it and separated by a small distance from said clamping means (10). The shield arrangement (20) can also made up of at least two rings (22) which are stacked with a small mutual separation, above said clamping means (10). The material of said shield arrangement (20) can be covered with a film of dielectric material and electrically connected to ground (23) through said substrate holder (3).