Method for manufacturing vibration element

A method for manufacturing a vibration element including:

• a base portion;
• and
• a first vibrating arm and a second vibrating arm extending from the base portion along a first direction and arranged along a second direction intersecting the first direction,
• the first vibrating arm and the second vibrating arm each including a first surface and a second surface arranged in a third direction intersecting the first direction and the second direction and on front and back sides, respectively, a bottomed first groove opened in the first surface, and a bottomed second groove opened in the second surface, the method comprising:
• a preparing step of preparing a quartz crystal substrate having the first surface and the second surface;
• a first protective film forming step of forming a first protective film on the first surface of the quartz crystal substrate, excluding first groove forming regions where the first grooves are formed and an inter-arm region located between a first vibrating arm forming region where the first vibrating arm is formed and a second vibrating arm forming region where the second vibrating arm is formed;
• a first dry etching step of dry etching the quartz crystal substrate from a first surface side via the first protective film and forming the first grooves and contours of the first vibrating arm and the second vibrating arm on the first surface;
• a second protective film forming step of forming a second protective film on the second surface of the quartz crystal substrate, excluding second groove forming regions where the second grooves are formed and the inter-arm region;
• and
• a second dry etching step of dry etching the quartz crystal substrate from a second surface side via the second protective film and forming the second grooves and contours of the first vibrating arm and the second vibrating arm on the second surface, wherein
• Wa/Aa<1 in at least one of the first dry etching step and the second dry etching step,
• Wa is a depth of the first grooves formed in the first dry etching step and a depth of the second grooves formed in the second dry etching step, and
• Aa is a depth of the contours formed in the first dry etching step and a depth of the contours formed in the second dry etching step.