A first interconnection is formed along a groove of a substrate and on a bottom surface of the groove, and has a first thickness. A second interconnection is electrically connected to the first interconnection and has a second thickness larger than the first thickness. An acceleration sensing unit is electrically connected to the second interconnection. A sealing unit has a portion opposed to the substrate with the first interconnection therebetween, and surrounds the second interconnection and the acceleration sensing unit on the substrate. A cap is arranged on the sealing unit to form a cavity on a region of the substrate surrounded by the sealing unit. Thereby, airtightness of the cavity can be ensured and also an electric resistance of the interconnection connected to the acceleration sensing unit can be reduced.