A simple and cost-effective possibility is proposed for producing optically transparent regions (5, 6) in a silicon substrate (1), by the use of which both optically transparent regions of any thickness and optically transparent regions over a cavity in a silicon substrate are able to be implemented.For this purpose, first at least a specified region (5, 6) of the silicon substrate (1) is etched porous. Thereafter, the specified porous region (5, 6) of the silicon substrate (1) is oxidized.