We synthesized suspended single-walled carbon nanotubes (SWNTs) by the thermal chemical vapor deposition method and functionalized them with Au nanoparticles (NPs). We used 3-(aminopropyl)triethoxysilane as a linker and controlled the Au NP density on the SWNT surface by changing the reaction time. In the Raman scattering spectra of the Au-functionalized SWNTs, an enhanced peak frequency and peak intensity were observed in the non-resonant region. A significant enhancement of the metallic character in the high frequency region was also observed, especially when we used a 633 nm laser. By measuring the electric properties using a standard field effect transistor configuration, we found that charge transfer occurred during the functionalization processes. It is expected that the charge transfer related optical enhancement may affect the observed change in the Raman profiles.