Batch fabrication of miniaturized apertures by thermal oxidation of structured silicon wafers at temperatures below the glass temperature of silicon dioxide has proven to be an adequate technological process. It exploits the retarded oxide growth due to the compressive mechanical stress distribution at concave structures in the silicon dioxide layer to obtain single and double aperture tips with 170-190 nm dimensions. Numerical simulations performed to investigate this phenomenon are in good agreement with experimental results, Furthermore, an improved technological process is presented to reduce the aperture size of silicon dioxide tips to 100 nm. It is explained in view of the theological behavior of silicon dioxide at elevated temperatures of 1100 degreesC, A further reduction of the aperture dimension down to 50 nm is achieved by deposition of thin metal films.