The paper represents the design and fabrication of an electrostatic micro actuator with $p^+$, Si cantilevers. The micro actuator consists of a plate suspended by four $p^+$,/TEX> silicon cantilevers and an electrode on a glass substrate. The $p^+$, Si structure is fabricated by the boron diffusion process and the anisotropic wet etch process. The cantilevers of the micro actuator curl down because of the residual stress gradient in $p^+$,/TEX> silicon. When the electrostatic forec is applied to the <TEX>$p^+$,/TEX> cantilevers, the vertical displacement of the plate can be achieved. The deflection of the cantilever due to the residual stress gradient and the vertical displacement by electrostatic force were calculated. The displacement of the plate was measured with a laser displacement meter for various input voltages and frequencies. The feasibility of the proposed micro actuator for the applications to optical pickup devices or optical communication devices was confirmed by the experiments.