Acceleration sensor element, acceleration sensor, and method of manufacturing the same

An acceleration sensor element comprising:

• a weight;
• a support having a lower end surface and a hollow part, said support being disposed around the weight as a center;
• a flexible plate disposed horizontally across the support so as to suspend the weight at the center of the hollow part of said support;
• at least one piezoelectric element disposed on the flexible plate, and comprising a piezoelectric body sandwiched by at least one set of electrodes,
• wherein acceleration applied from the exterior is converted to a deflection of said flexible plate based on the behavior of said weight corresponding to the acceleration, and the direction and the rate of said acceleration are three-dimensionally determined by electric charges generated from said piezoelectric body corresponding to the deflection of the flexible plate;
• wherein the piezoelectric elements are disposed continuously over the flexible parts of the flexible plate from at least one of the upper part of the weight and the support at the plane of projection seen from the upper part of said flexible plate;
• and
• wherein narrow grooves communicating with at least a space at the side of an outer periphery of the support are formed at positions on the lower end surface of the support, said grooves being symmetric with respect to straight lines passing through a center of the support and parallel to a plane including the support lower end surface.