The present invention relates to an electronic part used for mobile communications apparatuses and the like, and more particularly to an electronic part, such as an acoustic surface-wave device, a piezoelectric ceramic device or the like, which requires an oscillation space near the surface of the functional device chip thereof, and a method of production thereof. With this method, a space retainer for forming a sealed space at the functional portion of the chip can be hermetically sealed and have high moisture resistance, and the process of forming the space retainer can be carried out easily.The electronic part of the present invention comprises a functional device chip, a space retainer for forming a sealed space at the functional portion of the chip, a circuit substrate to which the chip is secured, electrode interconnection portions for establishing electric connection between the chip and the circuit substrate, and a sealing resin for covering and sealing at least the space retainer, wherein the space retainer comprises a support layer made of a synthetic resin film, provided with an opening enclosing the functional portion and joined onto the main surface, and a cover formed and joined onto the support layer so as to cover the functional portion and form a sealed space between the cover and the functional portion.