The present invention inter alia relates to a supported silica bilayer (SiO2 bilayer) film. In the supported silica bilayer film, the silica bilayer film consists of two atomic layers of corner-sharing SiO4 tetrahedra, forms in itself a chemically saturated structure and contains pores. The silica bilayer film has a first (1) and a second side (2) and is supported on the first side (1) by a removable polymer film. The invention further relates to a process for producing the supported silica bilayer film, a process for transferring a silica bilayer film, a free-standing silica bilayer film, a stack comprising a plurality of silica bilayer films, a filed-effect transistor having a gate oxide comprising the silica bilayer film or a stack thereof and the use of a silica bilayer film.