Patent ID: 8691377

Claim:
A semiconductor device comprising: a supporting board; an electrode surface processing layer formed on the supporting board; a semiconductor element; and a solder material containing a first metal composed mainly of bismuth and a second metal having a higher melting point than the first metal and joining the electrode surface processing layer and the semiconductor element, the solder material containing particles of the second metal inside the first metal, wherein a composition ratio of the second metal is higher than the first metal in a region of the solder material corresponding to a center portion of the semiconductor element, a composition ratio of the first metal is higher than the second metal in a region of the solder material outside the region corresponding to the center portion, and the composition ratio of the second metal is at least 83.8 atomic percent in the region corresponding to the center portion, and a thermal conductivity of the second metal is not lower than 35 W/(m·K).