Single-side microelectromechanical capacitive accelerometer and method of making same

In a method for making a high-sensitivity, microelectromechanical capacitive accelerometer including a proof mass having a thickness along an input axis of the accelerometer and first and second conductive electrodes from a single semiconductor wafer having a predetermined thickness, the improvement comprising:

• depositing first and second planar layers on a single-side of the wafer, the planar layers being relatively thin along the input axis;
• stiffening the first and second planar layers to form the first and second conductive electrodes, respectively, which are stiff so as to resist bending movement along the input axis;
• and
• forming substantially uniform, first and second narrow gaps between the first conductive electrode and the proof mass and between the second conductive electrode and the first conductive electrode, respectively, wherein the thickness of the proof mass is at least one order of magnitude greater than either the thickness of the first planar layer or the thickness of the second planar layer wherein the step of stiffening includes the step of forming stiffening ribs on at least one of the planar layers and wherein the step of forming the stiffening ribs includes the steps of forming trenches in the proof mass and refilling the trenches with a sacrificial layer having a substantially uniform thickness and an electrode material and wherein the step of forming the substantially uniform, first narrow air gap includes the step of removing the sacrificial layer.