Radar beams for searching a volume are selected by determining the central angle and azimuth and elevation extents to define an acquisition face. The drain region and the source region include a first conductivity type, the base region and the doped layer include a second conductivity type, and the second conductivity type is complementary to the first conductivity type. Through holes are formed in the upper case and the lower case, whereby undercut portions are not present in the projecting portions.