Proposed is a new type of packaging technology, 'pocket embedding package', using selectively anodised aluminium substrate. In this technology, chips can be embedded inside aluminium substrate so that an ultra-thin and compact type of package can be achieved. A monolithic microwave integrated circuit dice with 120 mu m thickness has been successfully embedded inside the substrate with a tolerance of less than 5 pm, and 300 mu m of total thickness can be achieved with excellent thermal dissipation.