Defining an oxide define region (ODR) without using a photomask is disclosed. Pad oxide and a stop layer are deposited over peaks of a substrate of a semiconductor wafer. The pad oxide may be silicon oxide, whereas the stop layer may be silicon nitride. Oxide, such as high-density plasma (HDP) oxide, is deposited over the pad oxide, the stop layer, and valleys of the substrate of the semiconductor wafer. A hard mask, such as silicon nitride, is deposited over the oxide, and photoresist is deposited over the hard mask. The photoresist is etched back until peaks of the hard mask are exposed. The peaks of the hard mask and the oxide underneath are etched through to the stop layer, and the photoresist is removed. Chemical-mechanical planarization (CMP) can then be performed on the hard mask that remains and the oxide underneath through to the stop layer, and the stop layer removed.