To improve the reliability of the mounting of an electronic component by installing a high airtight hold-down means, which has a plurality of electrodes on an opposed surface with a wiring board and is arranged on a single surface of the wiring board so as to cover the electronic component positioned and mounted on one surface of the wiring board and the inside of which is decompressed.

A semiconductor element 4 is positioned and mounted on that bumps 6 on each pad are placed on the corresponding lands 2A of a wiring board 3 respectively. A hold-down cap 5 is constituted with high airtightness, by integrally molding an inverted triangular sectional peripheral sidewall 5B to the underside peripheral end section of a top-face wall 5A, and the inside is decompressed in an approximately vacuum state. Accordingly, the semiconductor element 4 is fixed, so as to be pushed against the wiring board 3 by the internal side face of the top face wall 5A of the hold-down cap 5 by contraction stresses generated by negative pressure in the hold-down cap 5, and no stress in the lateral direction will be applied, because sliding is conducted even if relative places among the bumps 6 and the corresponding lands 2A are displaced.