Semiconductor integrated circuit devices having inverted frustum-shape contact layers

Claim 1

A semiconductor integrated circuit device including a bipolar transistor comprising a semiconductor substrate, a collector region, a base region and an emitter region which are spaced apart and formed at one surface of said semiconductor substrate, a plurality of inverted frustum-shape polycrystalline semiconductor contact layers having raised upper larger cross sectional surfaces and lower smaller cross sectional surfaces, one of said inverted frustum-shape polycrystalline semiconductor contact layers being formed on and in direct contact with each of said emitter region and said collector region, respectively, a first insulating film covering the raised side surfaces of said inverted frustum-shaped polycrystalline semiconductor contact layers and overlying the upper surface portions of said substrate which are included substantially within the vertical projection of the raised upper larger cross sectional surfaces of the inverted frustum-shape polycrystalline semiconductor contact layers down upon the upper surface of said substrate, a second insulating film covering the surface portions of said one surface of said substrate other than those areas covered by said first insulating film, the contact layers and said base region, a base electrode formed on said base region below the plane of the raised upper larger cross sectional surfaces of the inverted frustum-shape polycrystalline semiconductor contact layers and an emitter electrode and a collector electrode formed on the upper surfaces of the respective inverted frustum-shape polycrystalline semiconductor contact layers.