Appeal No. 96-1271
Application No. 08/190,388
The invention pertains to a semiconductor device
including a bipolar transistor. More particularly, a base
contact impurity region of the same conductivity type as the
base region, but having a higher impurity concentration than
the base region, is formed. The base contact impurity region
is at a depth shallower than a depth of the emitter impurity
region and the base contact impurity region is combined with a
metal silicide layer including one metal silicide selected
from the group consisting of titanium silicide, hafnium
silicide, vanadium silicide, tantalum silicide, molybdenum
silicide and tungsten silicide. Forming the higher impurity
concentration in the base contact impurity region is said to
prevent the increase in the base contact resistance which
occurs in conventional semiconductor devices during a silicide
reaction. Since the base contact impurity region is of a
higher impurity concentration, flow of impurities out of the
base contact impurity region during titanium silicide
formation, for example, does not result in an impurity
concentration in the base contact impurity region of such a
low concentration that base contact resistance would increase.
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