PURPOSE: To improve the humidity resistance of a semiconductor device by interposing a coupling agent having both a reaction group which chemically reacts with a lead material and a surface material and a reaction group which chemically reacts with a sealer between the lead material and the surface of a semiconductor element.

CONSTITUTION: A conductive adhesive 3 is dropped to the prescribed position of semiconductor element fixing lead wirings 1a of externally led wirings, and a semiconductor element 2 is placed on the agent. 1%-methylethyl ketone solution of γ-glycidoxypropyltrimetoxysilane is coated on the element 2 and lead wirings 1a, 1b, 1c, which are then heat treated to thermally cure the adhesive 3. Then, a plastic film which is contacted with the surface of the elements 2 and the wirings 1a, 1b, 1c can be formed. Thereafter, the element 2 is connected to the wirings 1a, 1b, 1c, and is transfer sealed with epoxy resin forming material 5. Then, the plastic film has strong adhesive with the material 5 and good water repellency, te humidity resistance can be improved.