An improved high temperature resistant backside metallization for compound semiconductors comprises a front-side metal layer formed on a compound semiconductor substrate; at least one via hole penetrating the compound semiconductor substrate, a top of an inner surface of the via hole is defined by the front-side metal layer; at least one seed metal layer, at least one backside metal layer and at least one diffusion barrier layer sequentially formed on a bottom surface of the compound semiconductor substrate and the inner surface of the via hole, the seed metal layer and the front-side metal layer are electrically connected through the via hole; a die attachment metal layer formed on a bottom surface of the diffusion barrier layer other than the via hole and an adjacent area near the via hole. The diffusion barrier layer prevents the backside metal layer from diffusing into the die attachment metal layer.