Current work reports the manufacturing and electrical characteristics of organic field-effect transistors (OFETs) in the top-contact bottom-gate configurations utilizing solution-processed poly (3-hexylthiophene) (P3HT) films as an active semiconducting layer and thermoplastic polyurethane (TPU) as gate insulator. A spin-coating chemical polymerization technology and an electrospinning tool for polymeric mats production were used to prepare uniform organic thin films with controlled thickness from their solutions. To form the gate-electrode a thin layer of metal such as gold (Au) or silver (Ag) was deposited on the glass surface substrates by thermal evaporation through a shadow mask. TPU insulating films with different thicknesses were electrospun from precursor solution on the substrates with or electrodes. Patterned and/or drain and source electrodes were deposited directly on the surface of as-fabricated P3HT organic semiconductor layer. We used two kinds of metals that have different work functions and their combinations to investigate the influence of the source, drain and gate electrode materials on the output characteristics of fabricated organic thin film transistors. All fabricated OFET devices showed typical p-type channel characteristics. Additionally, the effects of TPU-gate dielectric thickness as well as the influence of processing parameters on electrical performances of fabricated OFETs were also investigated. Results show that all developed transistors exhibit good and stable performance up to a relatively high drain voltage of similar to 50 V and the drain-source current up to similar to 0.5 mu A.