was formed higher quality oxide film was manufactured and the insulating property of the gate insulating layer of the graphene field effect transistor was improved as the oxygen plasma treatment pressure was reduced further the capacitance of the existing gate insulator having a total thickness of 6 4 nm using atomic layer deposition ald of alo x together with the self assembled monolayer sam was about 0 5 u03bcfcm u2212 2 and the leakage current was measured to be 10 u2212 7 acm u2212 2 at 3 v the capacitance of 0 5 u03bcfcm u2212 2 at 3 v induces an electric charge having the same quantity as that of the alo x capacitance of 1 5 u03bcfcm u2212 2 at 1 v in the case of the aluminum oxide capacitor of example 1 and the gate leakage current is 10 u2212 8 acm u2212 2 through alo x at 1 v and lower than that of preceding research therefore since the gate insulator of example 1 has high capacitance the field effect transistor fet may be satisfactorily operated even at a low voltage of 1 to 1 5 v which means that it is suitable for adhering the field effect transistor to various materials and apparatuses to thus be portably.