We propose a realistic process for the excitation of surface plasmon polariton (SPP) modes in a silicon photonic waveguide (WG). The process involves the placement of buried oxide (BOX) composed of silica between a WG and silicon substrate. When the BOX thickness is manipulated, different amounts of modal power leak toward the BOX into the substrate and simultaneously acquire compensation from a semiconductor located on the WG. The compensation related to the leakage can be used to infer transparency gain. Similar to the case for a semiconductor laser cavity, the lowest transparency gain among WG modes can be favored; thus, only one mode can survive in the WG, and it is in the region with the specified BOX thickness. Finally, we propose a credible mechanism suitable for demonstrating the region requirements of the existence of SPP modes.