Circuit apparatus having electrostatic discharge protection function

A circuit apparatus having electrostatic discharge (ESD) protection function, comprising:

• a first circuit module, operating in a first power supply domain, comprising at least a first transistor;
• a second circuit module, operating in a second power supply domain different from the first power supply domain, comprising at least a second transistor;
• and
• a thick-oxide transistor, having a control terminal for receiving a control signal, a first terminal coupled to the first circuit module, and a second terminal coupled to the second circuit module, for selectively performing an ESD protection operation according to the control signal;
• wherein at least one of the first transistor and the second transistor is a thin-oxide transistor, the thick-oxide transistor is turned off by the control signal when an ESD event occurs, and the thick-oxide transistor is turned on by the control signal when the circuit apparatus is under normal operation.