In this paper the interaction between a trimethylsilylated silicon substrate and diazonaphthoquinone–novolak photoresist material has been examined. Time‐of‐flight secondary ion mass spectrometry (TOF SIMS) and contact angle measurements of water have been used to determine the surface coverage of trimethylsiloxy (TMS) groups on cleaned and subsequently treated silicon wafers. A linear relation is obtained between the relative surface coverage as measured by TOF SIMS and the cosine value of the contact angle. The surface coverage of the TMS groups has to exceed a value of about 50% of a monomolecular layer to assure the absence of lift‐off of photoresist. Contrary to the common belief that trimethylsilylation of silicon substrates improves the adhesion between photoresist and the silicon substrate, it rather deteriorates the adhesion. This is further corroborated by experiments on silica particles. It is proposed that the low‐surface energy of the trimethylsilylated surface prevents the penetration of the alkaline developer solution into the interface of the silicon substrate and the photoresist material.