PURPOSE: To uniformly press a metallic press-welding gate electrode to a semiconductor substrate by providing a metallic buffer member between the metallic press welding gate electrode and an extension.

CONSTITUTION: A step 40 corresponding to a metallic press-welding gate electrode 39 is provided with an insulating material layer 41 such as mica for example to approximately surround the metallic press-welding gate electrode 39 to ensure insulation as well as an elastic member 42 such as a coil spring for example is placed between them to have uniform pressing force applied. A metallic press-welding gate electrode edge 45 is provided with a metallic buffer member 46 between a sleeve 44 and the electrode 39. The form is like a strand, a mesh or a cushion wherein it is as long as 10 to 15 mm and as wide as 3mm while a diameter of a copper or copper alloy thin wire for the strand or the mesh is approximately 0.1mm. In summary, difference in rigidity of the electrode 39 and the gate electrode edge 45 is buffered by the buffer member 46 located between them. As a material, silver with small process-curing degree as well as copper and copper alloy are applicable.