Abstract: A monolithic silicon acceleration sensor capable of detecting acceleration along multiple orthogonal axes of acceleration is disclosed. The monolithic silicon acceleration sensor is micromachined from silicon to form one or more sensor cells, each sensor cell having an inertial mass positioned by beam members fixed to a silicon support structure. Movement of the inertial mass due to acceleration is detected by either a differential capacitance measurement between opposing surfaces of the inertial mass and electrically conductive layers on a top and a bottom cover plate structure, or by a resistance measurement of piezoresistive elements fixed to the positioning beam members. Embodiments of the invention are capable of detecting acceleration in a plane, along two orthogonal axes of acceleration, or along three orthogonal axis of acceleration.