A one-time programmable (OTP) memory device includes an access transistor, a word line, a voltage line, a well, a first filling oxide layer, a first semiconductor layer, and a bit line. The access transistor includes a gate structure on a substrate, and first and second impurity regions at portions of the substrate adjacent to the gate structure. The word line is electrically connected to the gate structure. The voltage line is electrically connected to the first impurity region. The well is formed at an upper portion of the substrate, and is doped with impurities having a first conductivity type. The first filling oxide layer is formed on the well. The first semiconductor layer is formed on the first filling oxide layer, and is doped with impurities having the first conductivity type and electrically connected to the second impurity region. The bit line is electrically connected to the well.