PREPARATION OF FIELD EFFECT TRANSISTOR

摘要

PURPOSE:To eliminate the need for a wire for connecting electrodes of a field effect transistor and improve its radiating efficiency by making a concave portion for forming a main electrode in the upper surface of a semiconductor substrate and allowing the electrode provided in the concave portion to directly contact with a plated heat sink provided on the substrate lower surface. CONSTITUTION:A concave portion 9 is made in an N type layer 2 on a semiinsulative substrate 1, extending into the substrate 1. The layer 2 is etched so as to leave only a portion of it extending over one of the edges of the concave portion 9 and the central portion of the substrate 1. Then a source electrode 3 is formed covering the side walls and bottom of the concave portion 9 and extending on the end of the remaining layer 2, and a gate electrode 5 and a drain electrode 4 are provided on the layer 2. After that, with only the circumference left, the lower surface of the substrate 1 is etched to allow the electrode 3 at the bottom of the concave portion 9 to be exposed, and the whole lower surface of the substrate 1 is coated with a metal layer 10 so that it contacts with the electrode 3. Then a resist layer 11 is provided on the circumference of the substrate lower surface, and a plated heat sink 12 is secured through a plated layer 14 to the layer 10 surrounded with the resist layer 11. Thus, the sink is used also as an electrode material.