Method for manufacturing semiconductor device and semiconductor device

The present invention relates to a method for manufacturing a semiconductor device and a semiconductor device, which are high in generality, can perform semiconductor chip mounting with an excellent reliability under a high temperature environment, and can perform high temperature motion of a semiconductor device. Between a mounting substrate and the semiconductor chip a joint support layer is clamped, through maintaining the temperature to be higher than the melting point of a melt layer, then an alloy layer is formed which has a higher melting point than the melt layer by liquid phase diffusion, such that the mounting substrate is jointed with the semiconductor chip. The joint support layer includes 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.