We report the influence of dip-coating speed and concentration of the polymer solution on the characteristics of field-effect transistors (FETs) fabricated in the bottom-contact structure with regioregular poly(3-hexylthiophene) (RR-P3HT) as the active semiconducting material. For each concentration of the polymer in solution, there is an optimum dip coating speed for film deposition with highest field effect mobility; for example, with chloroform as solvent the optimum speed is 0.5mm/min for a solution containing 1.0mg/ml and 1.0mm/min for a solution containing 2.5mg/ml. Based upon AFM studies of the resulting film morphology, we conclude that the formation of a “rod-like” morphology is the origin of the improved carrier transport in the FET channel.