High-voltage semiconductor device

A high-voltage semiconductor device includes a substrate, a body region, a well region, a bulk region, a source, a drain, an isolation region, a gate structure, and a resistor. The body region and the well region are disposed in the substrate. The bulk region and the source are disposed in the body region. The drain is disposed in the well region. The isolation region is disposed on the well region. The isolation region is disposed between the drain and the source. The gate structure is disposed on the substrate. The gate structure extends onto a portion of the isolation region. The resistor is disposed on the isolation region. The resistor is electrically connected to the bulk region and the drain, or the resistor is electrically connected to the drain and/or the source.