A heterodyne laser having a first optical path for guiding excitation light and a second optical path for guiding measurement light. The replica bias circuit has a first reference current source transistor, a second reference current source transistor and a reference node corresponding to the output terminal of the charge pump core circuit. In one group of processes a directional deposition of silicon oxide is performed after the trench has been etched, yielding a thick oxide layer at the bottom of the trench. The separating element may be a sheet having a low-coefficient of friction surface, and the target may be disposed on the low-coefficient of friction surface of the separating element.