Abstract: A field effect transistor includes a source electrode (30) and a drain electrode (29) formed to be spaced apart from each other on a semiconductor substrate (2), a gate electrode (22) disposed between the source electrode (30) and the drain electrode (29), and a field plate electrode (24, 26) disposed via an insulating film (21) above the semiconductor substrate (2) in a region between the gate electrode (22) and the drain electrode (29), wherein a surface of the semiconductor substrate (2) is flat, and a distance between the semiconductor substrate (2) and the field plate electrode (24, 26) increases according as it goes along a direction from the gate electrode (22) towards the drain electrode (29). With this field effect transistor, the breakdown voltage BVdss is ensured; the chronological change in the set current is restrained; and the on-resistance of an amplifying element is reduced.

Abstract: A semiconductor package comprises a semiconductor chip, an interposer substrate, a plurality of unfilled end face through holes arrayed at the periphery of the semiconductor package, a plurality of inner through holes, a plurality of end face through hole electrodes each formed inside the end face through holes so as to be exposed on a side face of the semiconductor package and a plurality of inner electrodes each formed around openings of the inner through holes on the other side of the interposer substrate, the semiconductor chip being mounted on one side of the interposer substrate, the electrodes being laid out in an array on the other side of the interposer substrate.