BiCMOS device with low bandgap CMOS contact regions and low bandgap bipolar base region

Claim 1

A semiconductor device comprising: a substrate made of a first semiconductor material; first, second and third regions each including a semiconductor material, formed on the substrate, and isolated from each other by element isolation oxide films; a bipolar transistor formed in the first region, and having a collector formed in the substrate, a base constituted by a first film made of a second semiconductor material and formed on the substrate, and an emitter constituted by a semiconductor film formed on the first film; a n-channel MOSFET formed in the second region, and having n-type source and drain regions formed in a p-type region of the substrate, an n-type second film made of a semiconductor material having a composition substantially the same as that of the second semiconductor material and formed on each of the n-type source and drain regions, and a metal electrode formed on the second film, wherein an energy difference between a conduction band of the second film and a vacuum level is larger than an energy difference between a conduction band of the n-type source and drain regions and the vacuum level; and a p-channel MOSFET formed in the third region, and having p-type source and drain regions formed in an n-type region of the substrate, a p-type third film made of a semiconductor material having a composition substantially the same as that of the second semiconductor material and formed on each of the p-type source and drain regions, and a metal electrode formed on the third film, wherein an energy difference between a valence band of the third film and the vacuum level is smaller than an energy difference between a valence band of the p-type source and drain regions and the vacuum level; wherein the first, second, and third films are derived from one film made of a semiconductor material having a composition substantially the same as that of the second semiconductor material.