New protective coating layers for use in wet etch processes during the production of semiconductor and MEMS devices are provided. The layers include a primer layer, a first protective layer, and an optional second protective layer. The primer layer preferably comprises an organo silane compound in a solvent system. The first protective layer includes thermoplastic copolymers prepared from styrene, acrylonitrile, and compatible compounds such as monomers, oligomers, and polymers comprising epoxy groups; poly(styrene-co-allyl alcohol); and mixtures thereof. The second protective layer comprises a highly halogenated polymer such as a chlorinated polymer which may or may not be crosslinked upon heating.