Patent ID: 8796766

Claim:
A semiconductor device, comprising: a laterally double diffused metal oxide semiconductor (LDMOS) transistor formed on a first portion of an epitaxial layer, wherein the epitaxial layer is a first conductive type; a bipolar transistor formed on a second portion of the epitaxial layer; and a guard ring formed between the first portion of the epitaxial layer and the second portion of the epitaxial layer, wherein the guard ring substantially prevents electrons generated by a forward bias operation of the LDMOS transistor from moving into the bipolar transistor when an isolation voltage is applied to the guard ring, wherein the bipolar transistor comprises: a buried layer of a second conductive type, wherein the buried layer is connected to the guard ring, a second extension region of the first conductive type having a contact surface with the buried layer, the second extension region is formed through a ion implantation of a first conductive type impurity, a first extension region of the second conductive type formed within the second extension region, wherein the first extension region includes a collector region and an emitter region, and a base region formed between the guard ring and the second extension region.