The present invention provides ester group-containing tertiary amine compounds of the formula (R.sup.1OCH.sub.2CH.sub.2).sub.nN(CH.sub.2CH.sub.2CO.sub.2R.sup.2).sub.3-- n which, when used as additives in chemical amplification photolithography, can yield photoresists having a high resolution and an excellent focus margin. The present invention also provides a process comprising the step of subjecting a primary or secondary amine compound to Michael addition to an acrylic ester compound; a process comprising the steps of subjecting monoethanolamine or diethanolamine to Michael addition to an acrylic ester compound so as to form an ester group-containing amine compound and introducing a R.sup.1 group to the resultant ester group-containing amine compound; and a process comprising the step of effecting the ester exchange reaction of an ester group-containing tertiary amine with R.sup.2OH.