Semiconductor device and method for fabricating the same

A method of fabricating a semiconductor device having a laterally double diffused metal oxide semiconductor (LDMOS) transistor and a bipolar transistor, the method comprising:

• forming an epitaxial layer over a semiconductor substrate, wherein the epitaxial layer is a first conductive type;
• forming a buried layer by implanting impurity ions into a first portion of the epitaxial layer in which the bipolar transistor is to be formed, wherein the buried layer is a second conductive type, wherein the second conductive type has an opposite polarity to the first conductive type;
• forming a guard ring connected to an upper portion of one side of the buried layer;
• forming a first extension region by implanting impurity ions of the first conductive type into a portion of the epitaxial layer, wherein the first extension region partially overlaps the buried layer, wherein the first extension region is in contact with the buried layer;
• forming a second extension region of the second conductive type within the first extension region through a second conductive type impurity ion implantation process;
• implanting impurity ions of the first conductive type into both a portion of the second extension region and a region between the guard ring and the first extension region to form a first conductive well junction and a well, wherein the first conductive well junction and the well are of the first conductive type;
• implanting impurity ions of the second conductive type to form an emitter region within the first conductive well junction and to form a collector region within the second extension region, wherein the collector region is isolated from the emitter region by a preset distance;
• and
• implanting impurity ions of the first conductive type into the well to form a base region within the well.