Semiconductor device and heat sink with 3-dimensional thermal conductivity

A semiconductor device, comprising:

• a semiconductor element having a rectangular two-dimensional geometry and serving as a heat source;
• a first heat sink section comprising said semiconductor element mounted thereon;
• and
• a second heat sink section joined to an opposite side of said first heat sink section that comprises said semiconductor element,
• wherein a relation among directional components of a thermal conductivity of said first heat sink section is:
• K1yy≧K1xx>K1zz,
• wherein the thermal conductivity of said first heat sink section is defined as K1, and directional components of a three-dimensional thermal conductivity of said first heat sink section in X, Y, and Z directions are determined as K1xx, K1yy, and K1zz, and
• wherein a relation among directional components of a thermal conductivity of said second heat sink section is:
• K2zz≧K2yy>K2xx or K2yy≧K2zz>K2xx,
• wherein the thermal conductivity of said second heat sink section is defined as K2, and the directional components of the thermal conductivity of said second heat sink section in X, Y, and Z directions are determined as K2xx, K2yy, and K2zz.