The invention concerns a photolithographic method of producing sub-micron structural features by applying to a substrate a photosensitive resist layer consisting of a polymer containing tert-butyl ester or tert-butoxycarbonyloxy groups, a photosensitive component (in the form of an ester of naphthoquinonediazide-4-sulfonic acid and an aromatic hydroxy compound) and a suitable solvent. The photoresist is then dried, exposed in an imaging manner, subjected to a temperature treatment in the range between 120.degree. and 150.degree. C. for a period of 100 to 600 seconds, and wet-developed (single-layer resist system). The invention also concerns a method in which a corresponding two-layer resist system is used.