A negative resist system utilizing acid-catalyzed intramolecular esterification of δ-hydroxy acid has been developed for ArF phase-shifting lithography. The system is made up of an acrylate polymer with pendant structure of androsterone derivative with δ-hydroxy acid and a photo-acid generator. We investigated the effect of the comonomer and found that it changes the affinity of the resist polymer to the aqueous base developer. The change of the polarity of the comonomer was found to drastically affect the dissolution properties and the resolution capability. Optimization of the δ-hydroxy acid content and the developer concentration prevented pattern deformation such as "winding lines" and scum between the lines. The improved resist formulation combined with an ArF excimer-laser stepper with a phase-shifting mask produced a clearly resolved 100-nm line-and-space patterns.