In this work, we employed two nontoxic green chemistry methods to develop solution-processed copper oxide Cu_xO thin films at low annealing temperature of 200 °C. The first aqueous precursor of Cu_xO was prepared by mixing the copper powder with spinach leaves extract, whereas the other solution was formulated using the water-based polyol reduction method of Cu(II) nitrate. The as-prepared precursors were then spun on SiO₂/P⁺ Si substrates to form nanoscale Metal-Oxide-Semiconductor (MOS) capacitors by which some valuable information about the Cu_xO semiconductor films and their interfaces with dielectric were acquired. Both fabricated MOS capacitors exhibited p-type polarity with negative flat-band voltages. However, the MOS based on spinach extract-Cu_xO films showed small hysteresis of 100 mV, which could be attributed to its large grain size that sequentially leads to smooth interface and less trap density.