| 摘要 |
PURPOSE:To avoid peeling-off of a resin layer by a method wherein protective resin is applied only to the bottom parts among a plurality of bottom parts which have the smallest difference in level from a main surface. CONSTITUTION:Impurities are diffused from one or both surfaces of an N-type silicon wafer which has a predetermined specific resistivity and thickness. Then mesa etching is selectively applied to the main surface of the wafer twice to form recessed parts 10 composed of bottom parts 11 and bottom parts 12 which have varied differences in levels from the main surface 20. Then a heat oxide film 22 is formed on the substrate surface of the main surface 20 side and patterned to drill contact holes 23. A heat buffer plate 7 made of Mo or W is welded and alloyed with the substrate main surface of the opposite side with solder of Al or the like. Then Al is evaporated on the main surface and patterned to form cathodes 8 and 8d and a gate electrode 9. Then polyimide resin is applied and patterned to form protective resin layers 21 only on the bottom parts 11. With this constitution, as the resin layers do not cover the stepped parts, adhesiveness with the bottom parts is high and peeling-off can be avoided.
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