Abstract: An organic field effect transistor (OFET) having a block copolymer (BCP) layer is provided. The OFET includes a gate, an optional dielectric layer, a BCP layer, an organic semiconductor layer, a drain, and a source. The BCP layer is formed between the dielectric layer and the organic semiconductor layer when the dielectric layer exists. Otherwise, the BCP layer is formed between the gate and the organic semiconductor layer when the dielectric layer does not exist. When being positioned between the gate and the organic semiconductor layer without the dielectric layer, the BCP layer also functions as a dielectric layer. Inclusion of the BCP layer enhances the electrical properties, such as the charge carrier mobility, of the OFET.