A high voltage operating field effect transistor has a source region and a drain region spaced apart from each other in a surface of a substrate. The source region is operative to receive at least one of a signal electric potential and a signal current. A semiconductor channel formation region is disposed in the surface of the substrate between the source region and the drain region. A gate region is disposed above the channel formation region and is operative to receive a bias electric potential having an absolute value equal to or larger than a first constant electric potential which changes according to an increase or decrease in a drain electric potential. A gate insulating film region is disposed between the channel formation region and the gate region.