A movable part formed on a substrate and adapted to be displaced in a direction parallel to the sheet surface of the substrate, a fixing part formed and fixedly mounted on the substrate, and springy hinges extending parallel to the sheet surface of the substrate and having their opposite ends connected to the movable part and the fixing part for supporting the movable part in a displaceable manner are provided. As viewed in cross section in a plane perpendicular to the lengthwise direction of the hinges, the hinge has a width which is diminishing as the top surface of the substrate is approached, thus having a trapezoidal or triangular cross section. A width as measured on the top surface of the hinge which is required to provide an equivalent spring constant can be chosen to be greater than the width of a hinge having a rectangular cross section (constant width), and this facilitates the implementation of the photolithography during the manufacture.