To manufacture and supply a micro-bench for realizing a high S/N and high speed and inexpensive semiconductor module.

In this micro-bench to be used for mounting an optical fiber, this substrate is constituted of ceramics whose specific resistance is 109 Ω.cm or more, and whose specific dielectric constant is 15 or less. In this case, a groove on which an optical fiber is mounted is arranged on the surface, and a semiconductor element mounting part on which an optical semiconductor is mounted is arranged at the edge of the groove, and a positioning mark for mounting a semiconductor is arranged at the semiconductor element mounting part. Also, the ceramics is constituted of AlN or AlN as main components.