Patent ID: 8178893

Claim:
A semiconductor element mounting substrate comprising: a substrate body formed of a diamond composite material in which a number of diamond particles are bonded by a bonding material, the substrate body having a finished connecting surface to be connected with another member such that a number of at least either recesses or protrusions having a depth or height of 10 μm to 40 μm and a surface-direction diametrical size of 10 μm to 3 mm, per unit area of the finished connecting surface, is between 3/cm 2 and 50/cm 2 , on at least the finished connecting surface of the substrate body, a coating layer formed of a solder or a brazing material being formed in a manner filling and covering the recesses or protrusions, and the coating layer having a thickness in a region of the finished connecting surface other than the recesses or protrusions of 1 μm to 30 μm, an arithmetic mean roughness R a of a roughness curve showing a surface roughness of R a ≦2 μm, and a maximum height roughness R z of R z ≦15 μm.