Abstract: According to one embodiment, between the mounting substrate and the semiconductor chip, there is a joint support layer including a metal or its alloy selected from the group of Cu, Al, Ag, Ni, Cr, Zr and Ti and a melt layer laminated across the joint support layer, and formed of a metal selected from the group of Sn, Zn and In or of an alloy of at least two metals selected from the same metals. The process of joining the mounting substrate and the semiconductor chip includes intervening a joining layer which is formed, at least for its outermost layer, by the melt layer, maintaining the temperature to be higher than the melting point of the melt layer, then forming an alloy layer which has a higher melting point than the melt layer by liquid phase diffusion.