An apparatus comprises two n-type metal oxide semiconductor (MOS) devices formed next to each other. Each n-type MOS device further includes a pair of face-to-face diodes formed in an isolation ring. A method of modeling the apparatus comprises reusing four-terminal MOS device models in standard cell libraries and combining the four-terminal MOS device model and the isolation ring model into a 4T MOS plus isolation ring model. The method of modeling the apparatus further comprises adding a dummy device between a body contact of the first n-type MOS device and a body contact of the second n-type MOS device.