Abstract: Semiconductor devices which comprise a semiconductor chip, electrically conductive materials for connections to external leads, and encapsulated by a sealing resin has a surface and a portion of the electrically conductive material covered with a hardened silicone layer whose surface is exposed to ultraviolet radiation and the irradiation processed surface adheres to and is unified with the sealing resin. The sealing resin does not break easily when the device is exposed to heat cycles, thermal shock, repeated interruptions in current flow, and long periods of time at high temperature or low temperature. Such devices also exhibit excellent properties of moisture resistance, corrosion resistance and stress relaxation.