An organic thin film transistor including a fluorine-based polymer thin film and method of fabricating the same. The organic thin film transistor may include a gate electrode, a gate insulating layer, an organic semiconductor layer, source electrode, and a drain electrode formed on a substrate wherein a fluorine-based polymer thin film may be formed (or deposited) at the interface between the gate insulating layer and the organic semiconductor layer. The organic thin film transistor may have higher charge carrier mobility and/or higher on/off current ratio (I.sub.on/I.sub.off). In addition, a polymer organic semiconductor may be used to form the insulating layer and the organic semiconductor layer by wet processes, so the organic thin film transistor may be fabricated by simplified procedure(s) at reduced costs.