A semiconductor acceleration sensor (1) is formed by a cantilever (4) having a conductive movable electrode (5) of predetermined mass at one end, at least one pair of fixed conductive electrodes (8, 9) which are stationary with respect to the movable electrode (5) located on opposing sides of the movable electrode, and gaps provided between the movable electrode and the fixed electrodes. To prevent the movable electrode becoming fused to the contacted fixed electrode, in a first aspect of this invention, an insulating layer (6) is provided between the movable electrode and fixed electrodes, the layer being either on the movable electrode or on the fixed electrodes and in a second aspect of this invention the movable electrode or, preferably, the fixed electrodes, are formed of a high melting point material. In such a second aspect, to improve adhesion between the high melting point material and a substrate (3a, 3b) to which the fixed electrodes (8′, 9′) are mounted, a lower melting point material is firstly coated on said substrates. In a feature of the invention, a detector unit processing circuit (Figure 20) is described in which the output characteristic of the circuit may be digitally adjusted by suitable switching of a plurality of resistors (Rs, Rf), and in a second feature, the sensor chip and the detector unit integrated circuit are located on a common base (303) and mounted in a hermetically sealed chamber to prevent adverse environmental effects affecting operation of the sensor and detector unit assembly. A gas having a dew point of -40°C or lower is, advantageously, charged into the hermetically sealed chamber.