A released-beam sensor includes a semiconductor substrate having a layer formed thereon, and an aperture formed in the layer. A beam is mechanically coupled at a first end to the layer and suspended above the layer such that a second end forms a cantilever above the aperture. A boss is coupled to a second end of the beam and suspended at least partially within the aperture. The beam is configured to flex in response to acceleration of the substrate along a vector substantially perpendicular to a surface of the substrate. Parameters of the sensor, such as the dimensions of the beam, the mass of the boss, and the distance between the boss and a contact surface within the aperture, are selected to establish an acceleration threshold at which the boss will make contact with the contact surface. The sensor may be employed to deploy an airbag in a vehicle.