Switching circuit and semicondcutor device

Abstract

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.

1 - 2 . (canceled)  
   
   
       3 . An RF switching circuit, comprising: 
 a plurality of input/output terminals for inputting and outputting an RF signal;    a switch for opening and closing an electrical connection between the input/output terminals, and    a control line,    wherein 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, and    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; and    said RF switching circuit further comprising a diode provided between the control line and the inter-gate region, the diode having a cathode connected to the inter-gate region.    
   
   
       4 . The RF switching circuit of  claim 3 , wherein the number of said input/output terminals is three, 
 the RF switching circuit is an SPDT RF switching circuit including two said multi-gate field effect transistors each connected between each two of the input/output terminals, and    the inter-gate region of one of the multi-gate field effect transistors is connected to the inter-gate region of the other multi-gate field effect transistor.    
   
   
       5 . (canceled)  
   
   
       6 . An RF switching circuit, comprising: 
 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,    wherein 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, and    the multi-gate field effect transistor has a biasing gate used for applying a bias voltage and provided between the gates.    
   
   
       7 . The RF switching circuit of  claim 6 , wherein a voltage equal to or higher than 80% of a high-level voltage for turning the multi-gate field effect transistor ON and equal to or lower than the high-level voltage is applied to the biasing gate.  
   
   
       8 . The RF switching circuit of  claim 7 , wherein a voltage equal to or lower than 90% of the high-level voltage is applied to the biasing gate.  
   
   
       9 . The RF switching circuit of  claim 7 , wherein the high-level voltage is a power supply voltage.  
   
   
       10 . The RF switching circuit of  claim 6 , wherein the number of said input/output terminals is three, 
 the RF switching circuit is an SPDT RF switching circuit including two said multi-gate field effect transistors each connected between each two of the input/output terminals, and    a biasing line connecting the biasing gates of the multi-gate field effect transistors together is further provided.    
   
   
       11 . The RF switching circuit of  claim 10 , further comprising two shunt circuits each for causing one of the input/output terminals connected to one of the multi-gate field effect transistors to be grounded with respect to an RF signal, 
 wherein each of the shunt circuits is connected between one of the input/output terminals and a ground and constituted by a multi-gate field effect transistor including a biasing gate, and    the multi-gate field effect transistor constituting each of the shunt circuits is connected to the biasing line.    
   
   
       12 . The RF switching circuit of  claim 10 , wherein a voltage equal to the high-level voltage is applied to the biasing line.  
   
   
       13 . The RF switching circuit of  claim 12 , wherein the high-level voltage is a power supply voltage.  
   
   
       14 . The RF switching circuit of  claim 10 , wherein the biasing line is connected to the input/output terminals connected to the respective multi-gate field effect transistors.  
   
   
       15 . The RF switching circuit of  claim 10 , wherein the biasing line is provided with a level shift circuit for generating a voltage equal to or higher than 80% and equal to or lower than 90% of the high-level voltage.  
   
   
       16 . The RF switching circuit of  claim 15 , wherein the high-level voltage is a power supply voltage.  
   
   
       17 . The RF switching circuit of  claim 15 , wherein the level shift circuit includes: 
 two level shift diodes each having an anode connected to one of a pair of control lines for controlling the gates of the multi-gate field effect transistors and a cathode connected to the biasing line; and    two bias voltage adjusting resistors each having two terminals, one of the terminals is connected to an associated one of the control lines and the other terminal is connected to the biasing line.    
   
   
       18 . (canceled)  
   
   
       19 . A semiconductor device, comprising: 
 a semiconductor substrate; and    an RF switching circuit integrated on the semiconductor substrate,    wherein the RF switching circuit 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, and    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; and    the control line is connected between the gates of one of the multi-gate field effect transistors and the inter-gate region of the other multi-gate field effect transistor;    said semiconductor device further comprising an RF amplifier for amplifying RF power.    
   
   
       20 . A semiconductor device, comprising: 
 a semiconductor substrate; and    an RF switching circuit integrated on the semiconductor substrate,    wherein the RF switching circuit 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, and    the multi-gate field effect transistor has a biasing gate used for applying a bias voltage and provided between the gates.    
   
   
       21 . The semiconductor device of  claim 20 , further comprising an RF amplifier for amplifying RF power.