Patent ID: 8044488

Claim:
A semiconductor device comprising: a substrate provided with an epitaxial layer of a semiconductor having a certain thickness with a low impurity density, said epitaxial layer having a first area and a second area electrically isolated from each other; a first bipolar transistor having a first emitter region, a first base region and a first collector region formed in said first area and a first collector contact fixed to said first collector region, said first collector region including a first buried region of a high impurity density expanding underneath the first collector contact and said first base region so as to allow the first bipolar transistor to operate under a high frequency; and a second bipolar transistor having a second emitter region, a second base region and a second collector region formed in said second area and a second collector contact fixed to said second collector region, said second collector region including a high resistivity region of the epitaxial layer expanding underneath the second base region and a second buried region formed underneath the second collector contact but not underneath the second base region, said second buried region having an impurity density profile which is substantially the same as that of the first buried region of said first bipolar transistor so as to provide the second bipolar transistor with a high collector-emitter breakdown voltage; wherein the first and second base regions, the first and second emitter regions, and the first and second buried regions for the first and second bipolar transistors are formed through the same manufacturing processes applied to the substrate, respectively, whereby the first and second bipolar transistors are operable under a high frequency and with a collector-emitter breakdown voltage, and are formed on the same substrate through the same and simultaneous manufacturing processes applied to the epitaxial layer.