Abstract: A package structure in which conductive layers are provided on the lower surface of a circuit substrate provided with a semiconductor element mounted on the upper surface thereof, which conductive layers are connected to a conductive seal portion via conductive through holes, whereby both satisfactory air-tightness and satisfactory electromagnetic shielding characteristics of the package structure can be obtained. Projections consisting of high-temperature solder are formed as externally connecting electrodes, whereby a surface packaging operation can be carried out smoothly.