A switch semiconductor integrated circuit having a switch FET for controlling passage of a high-frequency signal so that the switch FET is switched between on-operation and off-operation. The switch semiconductor integrated circuit includes a logic control section using of an inverter circuit which generates the switching signal in accordance with a control signal applied from outside. The inverter circuit uses a junction-type FET in which the gate of the switch FET is connected to an output end of the inverter circuit via a gate resistor, and the output end is connected to a coupling capacitor which couples a part of the high-frequency signal. The coupled high-frequency signal is rectified by an equivalent diode between the gate and drain of the junction-type FET, and is superposed onto a DC voltage applied to the gate of the switch FET.
A method modifies dual gate transistor into a radio frequency switch. The method attaches a first signal input to a first gate of the transistor, attaches a second signal input to the source or drain of the transistor, attaches a common gate contact to the first gate and the second gate, attaches a signal output to a second gate of the transistor, attaches a source/drain contact connected to the source region or drain region where the second signal input is attached, and modulates the voltage supplied to the common gate and the source/drain contact to control the radio frequency switch.
