A tri-gated molecular field effect transistor includes a gate electrode formed on a substrate and having grooves in a source region, a drain region and a channel region, and at least one molecule inserted between the source and drain electrodes in the channel region. The effects of the gate voltage on electrons passing through the channel can be maximized, and a variation gain of current supplied between the source and drain electrodes relative to the gate voltage can be greatly increased. Thus, a molecular electronic circuit having high functionality and reliability can be obtained.