PURPOSE: To surely prevent electromagnetic wave coupling between high frequency signal input and output terminals by separating the cabinet space on the input terminal side of a semiconductor device from that on the output terminal side completely.

CONSTITUTION: The semiconductor device 10 for high frequency signal amplification is housed in a cabinet 8, and the cabinet is provided with internal space of length in accordance with the side length on the input terminal 13 side or the output terminal 14 side of the device 10. Also, a shielding block 11 provided with lover surface shape in accordance with the upper surface shape of the device 10 and also, height in accordance with the space height of the cabinet 8, and fixed in the cabinet 8 by placing on the device 10 is provided. Thereby, the space of the cabinet 8 on the input terminal 13 side can be separated completely from that of the cabinet 8 on the output terminal 14 side. As a result, it is possible to surely prevent the electromagnetic wave coupling between the high frequency signal input and output terminals without leaving the space of the cabinet 8 communicating between the input and output terminals 13, 14 of the semiconductor device 10 for high frequency power amplification.