Provided is an exhaust gas treatment catalyst including: a de-NOx catalyst; and a coating layer being provided on a surface of the de-NOx catalyst and containing at least one selected from the group consisting of alkali metal carbonates and alkaline earth metal carbonates. A belt member is stretched and circulated by a plurality of roller members. The negative ion beam source vacuum system preferably includes: a first pump turbo molecular pump, a large holding volume, and a semi-continuously operating pump. Other MEMS devices include support structures at least partially underlying a movable layer, where the portions of the support structures underlying the movable layer include a convex sidewall.