To realize a semiconductor device of a resin sealed or air-tight sealed type in which encapsulation leadless plating is carried out only to outer leads and which can completely prevent cell corrosion and can provide a good solderability and a good connectability, and also to realize a method for manufacturing the semiconductor device which can remarkably reduce its production cost.

In the method for manufacturing a resin sealed or airtight sealed semiconductor device, an underlying layer 9 of an Ni metal or Ni alloy film is coated on a surface of outer lead member 8 conducting an external device and a semiconductor chip 1 via bonding lines 4, and an Au metallic film 10 is coated on the underlying layer 9. In the method for manufacturing the semiconductor device, entire plating of encapsulated package is carried out over an entire surface of the outer leads after molded.