HIGH-FREQUENCY PART AND COMMUNICATION DEVICE

A high-frequency device having high-frequency-signal-treating circuits in and on a laminate substrate comprising pluralities of dielectric layers having conductor patterns, the high-frequency-signal-treating circuits having amplifier circuits and switch circuits; terminals including input and output terminals of high-frequency signals, the power supply terminals of the amplifier circuits and the power supply terminals of the switch circuits being formed on one main surface of the laminate substrate; power supply lines each having one end connected to each of the power supply terminals of the amplifier circuits and power supply lines each having one end connected to each of the power supply terminals of the switch circuits being formed on one dielectric layer to constitute a power supply line layer; a first ground electrode being arranged on the side of the main surface with respect to the power supply line layer, the first ground electrode overlapping at least part of the power supply lines in a lamination direction; a second ground electrode being arranged on the opposite side of the first ground electrode with respect to the power supply line layer, the second ground electrode overlapping at least part of the power supply lines in a lamination direction; and the high-frequency-signal-treating circuits being arranged on the opposite side of the power supply line layer with respect to the second ground electrode.