The disclosure is directed to wide band-gap semiconductor devices, such as power devices based on silicon carbide or gallium nitride materials. A power device die is attached to a carrier substrate or a base using sintered silver as a die attachment material or layer. The carrier substrate is, in some embodiments, copper plated with silver. The sintered silver die attachment layer is formed by sintering silver nanoparticle paste under a very low temperature, for example, lower than 200° C. and in some embodiments at about 150° C., and with no external pressures applied in the sintering process. The silver nanoparticle is synthesized through a chemical reduction process in an organic solvent. After the reduction process has completed, the organic solvent is removed through evaporation with a flux of inert gas being injected into the solution.