A medical device for surgical implantation adapted to serve as a drug delivery system has one or more drug loaded holes with barrier layers to control release or elution of the drug from the holes or to control inward diffusion of fluids into the holes. The barrier layers are non-polymers and are formed from the drug material itself by beam processing. The holes may be in patterns to spatially control drug delivery. Flexible options permit combinations of drugs, variable drug dose per hole, multiple drugs per hole, temporal control of drug release sequence and profile. Methods for forming such a drug delivery system are also disclosed. Gas cluster ion beam and/or accelerated Neutral Beam derived from an accelerated gas cluster ion beam may be employed.
