This study explores the use of a SiO2 interfacial layer in a Schottky diode to suppress unfavourable properties of the formed interface states. The deposition of the SiO2 layer improves the electrical properties of the device by reducing the interface state density. Before device fabrication, the following material characterisations, Raman, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were used, to measure the layer thickness, and investigate the elemental composition, and molecular structure of the deposited layer. Electrical characterizations were performed through current–voltage (I–V) and capacitance–voltage–frequency (C–V–f) measurements under both forward and reverse bias conditions after fabrication. The obtained results showed a reduction in interface state density (NSS) leading to improved device performance. Overall, the results are an indication that SiO2 serves as an effective passivation layer for minimising interface states, thereby enhancing the performance and reliability of Ni/n-Si Schottky diodes.