As　clinical　monitoring　of　intracranial　pressure　is　critical　to　the　treatment　of　brain　diseases,　the　piezoresistive　implantable　intracranial　pressure　(ICP)　sensor　based　on　silicon　bulk　micromachining　technology　for　medical　applications　hasbeen　developed.　In　this　paper,　the　design,　fabrication　and　test　of　the　sensor　are　described.　The　sensitivity　of　this　ICP　sensor　is　greatly　increased　while　the　size　is　kept　small.　By　analyzing　the　stress　distribution　of　sensitive　element　with　finite　element　method,　the　size　and　structure　of　the　sensor　are　determined.　Fabricated　on　an　n-type　single　crystal　silicon　wafer,　the　sensor　chip　is　mounted　in　the　capsule.　The　packaging　materials　of　the　sensor　are　of　biocompatibility　and　high　workability.　Test　results　demonstrate　that　the　sensor　features　a　sensitivity　of　10　μV/V/mmHg　at　room　temperature,　exhibits　a　linear　response　over　an　operating　pressure　range　of　-10-35　KPa　(-75-250　mmHg),　and　the　output　non-linearity　is　less　than　1.2%.　The　proposed　configuration　presents　its　advantages　in　drift　characteristic,　absolute　accuracy　and　sensitivity　compared　with　the　implanted　ICP　sensor　developed　before.　Due　to　the　tiny　dimension,　good　reliability　and　biocompatibility,　the　sensor　has　a　potential　used　for　biomedical　application.　©　2014　IEEE.