An electrostrictive or piezoelectric actuator device includes a solid state actuator element (4) that is elongated in the lengthwise direction (L) and contracted in the transverse direction (T) upon application of an electric voltage thereto. The actuator element (4) is clampingly held between a housing floor and an actuator output pin (6) in a housing (2). A protective interlayer (12) is respectively arranged between the lengthwise end faces of the actuator element (4) and the housing floor and the actuator pin respectively, to protect the actuator element against transverse stress peaks. The interlayer (12) provides a soft or elastic coupling in the transverse direction and a substantially rigid, force and stroke transmitting coupling in the lengthwise direction. To achieve this, each interlayer (12) is made of a material having an anisotropic modulus of elasticity with a lengthwise stiffness that is considerably higher than that of the solid state material of the actuator element and a transverse stiffness that is less than that of the solid state material of the actuator element.