A MEMS electrostatic actuator comprises first and second opposing electrode arrangements, wherein at least one of the electrode arrangements is movable. A dielectric material (24) is adjacent the one of the electrode arrangements (22). The second electrode arrangement is patterned such that it includes electrode areas (26) and spaces adjacent the electrode areas, wherein the dielectric material (24) extends at least partially in or over the spaces. The invention uses a multitude of electrode portions as one plate. The electric field lines thus form clusters between the individual electrode portions and the opposing electrode. This arrangement provides an extended range of continuous actuation and tunability.