Provided is a double gate field effect transistor and a method of manufacturing the same. The method of manufacturing the double gate field effect transistor comprises forming as many fins as required by etching a silicon substrate, masking the resultant product by an insulating material such as silicon nitride, forming trench regions for device isolation and STI film by using the silicon nitride mask, forming gate oxide films on both faces of the fins after removing the hard mask, and forming a gate line. As such, unnecessary channel formation under the silicon oxide film, when a voltage higher than a threshold voltage is applied to the substrate, is prevented by forming a thick silicon oxide film on the substrate on which no protruding fins are formed.