To provide a semiconductor device with its high-frequency electric signal transmission performance improved by preventing reflection or the like of high-frequency electric signals by first pads and second pads whereto semiconductor element electrodes are connected.

The semiconductor device is constituted of a semiconductor element accommodating package 8 comprising a substrate 1 and first pads 2 and second pads 3 formed on the substrate 1, and a semiconductor element 9 having electrodes 10 on its lower surface. The semiconductor element 9 is mounted on the semiconductor element accommodating package 8, and the electrodes 10 of the semiconductor element 9 are connected to the first pads 2 and the second pads 3 via connecting members 11. The plane area of a first pad 2 or a second pad 3 is ≤0.018 mm2. A connecting member 11 is constituted of a core made of a divinylbenzene resin or the like having a Young's modulus of ≤500 N/mm2and a jacket coating the core having an electric resistivity of ≤2×10-7Ω m.

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