the invention provides an aqueous alkaline developer solution for a positive - type photoresist layer for pattern - wise treatment of the surface of a substrate , e . g ., semiconductor wafer . the developer solution contains a tetraalkyl ammonium hydroxide , e . g ., tetramethyl ammonium hydroxide , and a trialkyl hydroxyalkyl ammonium hydroxide , e . g ., trimethyl hydroxyethyl ammonium hydroxide , as the essential ingredients and the temperature dependency of the development performance thereof is noticeably smaller than that of conventional developer solutions with respect to properties of the sensitivity of the photoresist and the thickness reduction of the photoresist layer in the unexposed areas , by virtue of the compensating temperature dependencies for these properties of these two ingredients for each other .