It is essential to secure the optical performance (sensitivity, FOM, plasmonic absorption strength, etc.), large-area fabrication, and physical durability to improve the usability of nanostructured SPR sensors. In this study, to ensure the physical durability of an Au-covered silica sphere monolayer (Au film over nanosphere (AuFON)) manufactured for use as an SPR sensor platform, the sensing performance and physical durability after TMOS treatment to bind spherical silica particles were investigated. The peel-off test showed that Au and silica constituting the AuFON did not fall off, and there was no significant difference in the sensing sensitivity and plasmonic absorption intensity before and after TMOS treatment. In addition, when colloidal Au nanoparticles (diameter of 5 nm) were applied to as-prepared AuFON and heat-treated, it was confirmed that the Au shells of the plasmonic particles were interconnected, and the Fano intensity increased from 3–5% to 22%.