An embodiment provides a semiconductor device integrated with a switch device and an ESD protection device, having electrostatic discharge robustness. Formed on a semiconductor substrate of a first type is a drain region of a second type opposite to the first type. The switch device has a source region of the second type, formed on the semiconductor substrate and with a first arch portion facing inwardly toward a first direction. The first arch portion partially surrounds the drain region. A control gate of the switch device controls electric connection between the drain region and the source region. The ESD protection device comprises a first region and a second region, both of the first type. The first region adjoins the drain region. The second region has a second arch portion facing inwardly toward a second direction opposite to the first direction, and the second arch portion partially surrounds the first region.