An accelerometer comprising: a substantially planar proof mass mounted to a fixed substrate by a support (18, 20), said proof mass being connected to the support (18, 20) by a compliant flexure (14, 16) so as to be linearly moveable in an out-of-plane sensing direction in response to an applied acceleration; the proof mass comprising first and second sets of moveable capacitive electrode fingers (50, 52) extending from the proof mass substantially perpendicular to the out-of-plane sensing direction in a first in-plane direction and laterally spaced in a second in-plane direction perpendicular to the out-of-plane sensing direction; and first and second fixed capacitor electrodes (42, 44) mounted to the fixed substrate, the first fixed capacitor electrode comprising a first set of fixed capacitive electrode fingers and the second fixed capacitor electrode comprising a second set of fixed capacitive electrode fingers; wherein the first and second sets of fixed capacitive electrode fingers (46, 48) extend in the first in-plane sensing direction and are laterally spaced in the second in-plane sensing direction; wherein the first set of fixed capacitive electrode fingers is arranged to interdigitate with the first set of moveable capacitive electrode fingers of the proof mass and the second set of fixed capacitive electrode fingers is arranged to interdigitate with the second set of moveable capacitive electrode fingers of the proof mass; wherein the first set of fixed capacitive electrode fingers has a thickness less than a thickness of the first set of moveable capacitive electrode fingers; and wherein the second set of fixed capacitive electrode fingers has a thickness greater than a thickness of the second set of moveable capacitive electrode fingers. a substantially planar proof mass mounted to a fixed substrate by a support (18, 20), said proof mass being connected to the support (18, 20) by a compliant flexure (14, 16) so as to be linearly moveable in an out-of-plane sensing direction in response to an applied acceleration; the proof mass comprising first and second sets of moveable capacitive electrode fingers (50, 52) extending from the proof mass substantially perpendicular to the out-of-plane sensing direction in a first in-plane direction and laterally spaced in a second in-plane direction perpendicular to the out-of-plane sensing direction; and first and second fixed capacitor electrodes (42, 44) mounted to the fixed substrate, the first fixed capacitor electrode comprising a first set of fixed capacitive electrode fingers and the second fixed capacitor electrode comprising a second set of fixed capacitive electrode fingers; wherein the first and second sets of fixed capacitive electrode fingers (46, 48) extend in the first in-plane sensing direction and are laterally spaced in the second in-plane sensing direction; wherein the first set of fixed capacitive electrode fingers is arranged to interdigitate with the first set of moveable capacitive electrode fingers of the proof mass and the second set of fixed capacitive electrode fingers is arranged to interdigitate with the second set of moveable capacitive electrode fingers of the proof mass; wherein the first set of fixed capacitive electrode fingers has a thickness less than a thickness of the first set of moveable capacitive electrode fingers; and wherein the second set of fixed capacitive electrode fingers has a thickness greater than a thickness of the second set of moveable capacitive electrode fingers.