▎ 摘　　要

NOVELTY - The FET has a step top gate medium layer (8) arranged on a metal source electrode (6). A metal drain electrode (7) is fixed between graphite electrodes. A top gate electrode (9) is formed with the step top gate medium layer. Edges of the metal source electrode and the metal drain electrode are arranged at equal distance, where distance value ranges from 100 nanometer to 1 micrometer. A double-layer graphene active area (5) is provided with the top gate electrode that is connected with the metal source electrode to cover a source area. The metal drain electrode is provided with a drain region. USE - Graphene FET. ADVANTAGE - The step top gate medium layer increases the source area between a channel and a gate tunneling window so as to obtain smaller electric current state. The FET improves ratio of a switching device. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a graphene FET preparation method. DESCRIPTION OF DRAWING(S) - The drawing shows a front sectional view of a graphene FET. Double-layer graphene active area (5) Metal source electrode (6) Metal drain electrode (7) Step top gate medium layer (8) Top gate electrode (9)