Appeal No. 2005-1256
Application No. 09/988,593
the threshold voltage of the resistor to fluctuate and cause unstable operation of the
transistor.
The prior art sought to prevent the well region from being implanted with the
source/drain impurity ions by increasing the thickness of the partial oxide film. This was
found to leave an undesirable residue on the partial oxide film and, although this residue
may be removed by etching, the increased time of etching can result in damage to a
gate oxide film adjacent the partial oxide film.
The instant invention solves the fluctuating resistance problem by forming a first
conductivity semiconductor region under an isolation film that at least partially has a
region doped by only an impurity of a first conductivity type. It is said that since the first
conductivity impurity region does not include second conductivity type impurities, the
resistance value of the body resistance can be reduced and dispersion can be
suppressed. Thus, a precisely controllable semiconductor device having a partially
isolated body fixed semiconductor-on-insulation (SOI) structure can be obtained without
increasing the resistance value of the body resistance.
Independent claim 1 is reproduced as follows:
1. A semiconductor device having an SOI structure formed by a
semiconductor substrate <1>, an embedded insulating layer <2> and an
SOl layer <3>, comprising:
a plurality of element forming regions provided in said SOI layer, each
formed with a prescribed element;
2
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