This letter reports, for the first time, on the design strategy and process integration for a small on-chip-antenna (OCA) with a radio-frequency identification (RFID) tag chip-area ∼1×0.5 mm2. It is designed based on a 2.45-GHz RFID tag circuit with an inductive-coupling model. A patterned Al shielding layer is used to improve the consistency of the actual performance obtained from fabricated devices and those predicated from the design. The antenna's inductor coils were fabricated based on a conventional Cu-Damascene process. To achieve the required antenna performance (e.g., Q-factor), a set of thick USG and deep-via etch processes were specifically developed. Our results demonstrate that the dc power converted by the OCA is sufficient to enable the RFID tag chip to communicate with a corresponding 2.45-GHz RFID reader with a 1-mm distance.