A method for enhancing surface characteristics of a fingerprint sensor and a protective structure made according to the method are disclosed. The method includes the steps of: providing a fingerprint sensor having a number of detecting elements beneath a top surface of the fingerprint sensor, the detecting element is used to detect changes of capacitance over a portion of a finger; forming a metal mesh layer over the top surface of the fingerprint sensor, wherein metal lines of the metal mesh layer are formed periodically and each of them is located between two adjacent detecting elements; forming a passivation layer on the metal mesh layer to shape a concave-convex top surface; and filling concave portions of the passivation layer with a Diamond-Like Carbon (DLC) material. A convex portion of the passivation layer is substantially above the metal line of the metal mesh layer.