Aromatic thermosetting copolyester (ATSP) has been recently introduced, which exhibits promising thermal, mechanical, and adhesive properties to address broad range of industrial applications. However, the ATSP resin has not been well described in terms of electronic properties. Hence, we used a thin film of ATSP as an interfacial layer between a metal and a semiconductor to control the properties of the metal-semiconductor contacts. In this study, ATSP oligomers were dissolved in tetrahydrofuran (THF) and multiple layers were deposited on a p-type Si wafer in thin film form by spin-coating technique. To obtain the metal and semiconductor device (Al/ATSP/ptype Si), Al was sputtered on the back surface of Si wafer as an Ohmic contact and the front surface as a rectifying contact. Morphological properties of the ATSP thin film were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Transmittance and band gap values of the ATSP thin film were determined by ultraviolet-visible (UV-Vis) spectrometry. Al/ATSP/p-type Si devices were characterized with I-V measurements under dark condition and with light illumination. These devices can potentially be developed for use as rectifiers and photodiodes.