An N-type high voltage device includes: a semiconductor layer, a well region, a floating region, a bias region, a body region, a body contact, a gate, a source and a drain. The floating region and the bias region both have P-type conductivity, and both are formed in a drift region in the well region. The bias region is electrically connected with a predetermined bias voltage, and the floating region is electrically floating, to increase a breakdown voltage of the high voltage device and to suppress turning-ON a parasitic transistor in the high voltage device.