Switching circuit and semicondcutor device

摘要

An RF switching circuit according to the present invention includes: a plurality of input/output terminals for inputting and outputting an RF signal; and a switch for opening and closing an electrical connection between the input/output terminals. The switch is constituted by a multi-gate field effect transistor including a plurality of gates located between source and drain spaced from each other on a semiconductor layer. A bias voltage is applied to an inter-gate region of the semiconductor layer between the gates. The bias voltage is equal to or lower than 90% of a high-level voltage, which is a voltage for turning the multi-gate field effect transistor ON, in a state where the multi-gate field effect transistor is ON, and is equal to or higher than 80% of the high-level voltage and equal to or lower than the high-level voltage in a state where the multi-gate field effect transistor is OFF.