This research presents the development of parylene thin-film deposition from the micrometer scale to nanometer scale. Processes improved film uniformity by 6% in the nanometer scale to meet the requirements of new applications of parylene, such as the delamination layer of organic light-emitting diodes, the dielectric film of through-silicon-via, and water-proofing mobile phones. The application and process of water-proofing mobile phones is also examined. The tested mobile phone was coated with a 0.5 μm parylene coating and functioned properly while submerged underwater. The mobile phone is still operational; thus, nanoscale parylene deposition is a novel application for water-proofing mobile phones. The application does not concern problems associated with parts assembly or damaged rubber material.