Silica-on-silicon structured channel erbium-doped waveguide amplifiers (EDWAs) were fabricated by a combination of the ion-exchange and sol-gel techniques. A small signal fiber-device-fiber net gain of $0.5\mathrm{dB}$ at $1531\mathrm{nm}$ was obtained for a $4\mathrm{cm}$ long EDWA with an optimized waveguide structure. The low noise figure of $4.0\mathrm{dB}$ was also achieved. Samples of different waveguide structures and rare-earth ion doping levels were fabricated to compare the EDWA gain properties. The results demonstrate that a better gain spectrum can be obtained by maximizing the distribution overlap of pump and signal mode intensity. The gain performance can be further improved by reducing upconversion efficiency of the EDWA. This work demonstrates that the ion-exchanged silica-on-silicon waveguide structure is an alternative approach for EDWA fabrication.