PURPOSE: To easily manufacture the semiconductor millimeter wave device with high precision and to decrease the transmission loss and deterioration of a signal by forming a groove or ridge on a semiconductor substrate as a waveguide and forming the waveguide, an element, and an input/output coupling device on the same substrate.

CONSTITUTION: The waveguide 2, a silicon element part 3, a high-frequency element part 4, and the input/output coupling device 5 are formed on the silicon substrate 1. The waveguide 2 is formed at the part 2' of the groove formed in the substrate 1, a metal layer 21 is formed on its bottom part and side wall, and a metal layer 22 is formed at the upper part to effectively confine an electromagnetic wave. Further, the element part 3 and an antenna 25 which sends and receives the electromagnetic wave are provided at specific places in the waveguide 2. The element part 3 is formed directly on the substrate 1. The input/output coupling device 5 transmits and receives electromagnetic waves inside and outside the substrate and is formed where the waveguide 2 and substrate end surface cross each other.