Abstract: A nitride-based wafer CVD device comprises a heat carrier, a nitride-based wafer, and a clamping ring. The heat carrier comprises a carrier surface. The nitride-based wafer is disposed on the carrier surface. The clamping ring is disposed above the carrier surface and the nitride-based wafer. The clamping ring comprises a tilted surface, and a polished surface, and the polished surface is opposite to the tilted surface. The nitride-based wafer has a plurality of HEMT devices. The polished surface and the carrier surface are parallel. A distance between the polished surface and the carrier surface in a first direction is in a range from 1.1 mm to 1.2 mm, and the first direction is parallel to a normal of the carrier surface.