A MEMS accelerometer uses capacitive sensing between two electrode layers. One of the electrode layers has at least four independent electrodes arranged as two pairs of electrodes, with one pair aligned orthogonally to the other such that tilting of the membrane can be detected as well as normal-direction movement of the membrane. In this way, a three axis accelerometer can be formed from a single suspended mass, and by sensing using a set of capacitor electrodes which are all in the same plane. This means the fabrication is simple and is compatible with other MEMS manufacturing processes, such as MEMS microphones.