This paper presents new results on miniaturized organic thin film transistors (TFT) fabricated on a spin coated polyimide (PI) film. Patterning steps, that are vital for the integrity and electrical performances of the organic TFT, were performed using resistless shadow-mask lithography with two high precision MEMS fabricated stencils, thus avoiding solvents and high temperature processes. Both pentacene and source-drain (S/D) electrodes were directly patterned through stencils with high accuracy on wafer scale. The TFT have been characterized before and after peeling the flexible PI film off the rigid surface, showing full transistor functionality in both cases.