A high-density 3-transistor cell one-time programmable (OTP) ROM array using standard CMOS Gate-Oxide antifuse (AF) is proposed, fabricated, and characterized with $0.18{mu}m$ CMOS process. The proposed non-volatile high-density OTP ROM is composed of an array of 3-T OTP cells with the 3-T consisting of an nMOS AF, a high voltage (HV) blocking transistor, and a cell access transistor, all compatible with standard CMOS technology.