Micromachine manufacturing method

A micromachine manufacturing method comprising at least:

• the step of preparing a silicon substrate having a single-crystal silicon layer on an upper surface via a buried oxide;
• the movable portion formation step of selectively etching the single-crystal silicon layer by using a movable portion formation mask pattern as a mask, thereby forming on the single-crystal silicon layer a movable portion which is coupled to the surrounding single-crystal silicon layer via a coupling portion on the buried oxide;
• the frame formation step of selectively etching away the silicon substrate from a lower surface by using as a mask a frame formation mask pattern having an opening, thereby forming a substrate opening in the silicon substrate and exposing a lower surface of the buried oxide in the substrate opening;
• the movable portion protective film formation step of forming a movable portion protective film on the single-crystal silicon layer so as to cover the movable portion while the movable portion is formed on the buried oxide;
• the buried oxide processing step of forming in a movable portion formation region of the buried oxide a movable portion opening which communicates with the substrate opening while the movable portion protective film is formed;
• and
• the step of forming a buried protective film which covers the movable portion exposed in the substrate opening and the movable portion opening, and the single-crystal silicon layer around the movable portion while the movable portion protective film is formed.