To use a TMAH (tetramethylanmonium hydroxide aqueous solution) developer with a resist based on adamantylmethacrylates, we proposed a cleavable adamantyl ester by protonic acid. We found that a 2-methyl-2-adamantyl ester was cleavable by protonic acid and poly(2MAdMA) (2-methyl-2-adamantylmethacrylate) worked as a chemically amplified resist with good sensitivity. We achieved high resolution by improving the adhesion. The 2MAdMA-MAA (methacrylic acid) resist achieved 0.165μm L/S with 3.0mJ/cm2 in ArF evaluation using a dilute TMAH developer. We could use a 2.38% TMAH developer by introducing 2MAdMA to the strongly polar acid labile protect group, OCMA (3-oxocyclohecylmethacrylate) or MLMA (mevalonic lactone methacrylate), which had good adhesion. We obtained fine patterns below 0.20μm at below 10mJ/cm2 in ArF evaluation with 2.38%TMAH developer. We achieved a minimum resolution with 0.15 pm L/S patterns and a D.O.FE of 0.6pm at 0.18μm L/S patterns using a 2MAdMA-MLMA resist.