Appeal No. 2004-0581
Application No. 09/041,105
wherein during certain loads of operation the n-type low density
well 4 is fully depleted. With reference to Figure 8 of the
appellants’ drawing, a sixth embodiment of the device (see claim
10) comprises a p-type substrate 1, an n-type high density well
2, a p-type epitaxial region 3, an n-type low density well 4 and
a left-behind portion of p-type epitaxial region 3a, wherein
during certain modes of operation the n-type low density well 4
is fully depleted. This appealed subject matter is adequately
illustrated by independent claims 1 and 10 which read as follows:
1. A semiconductor device having a separation
structure for high withstand-voltage comprising:
a first-conduction-type semiconductor substrate;
a first region comprising a second-conduction-type well
relatively high in impurity density, said second-conduction-
type well being formed on a surface of said first-
conduction-type semiconductor substrate;
a first-conduction-type epitaxial region formed on said
first-conduction-type semiconductor substrate above said
second-conduction-type well; and
a second region comprising a second-conduction-type
well relatively low in impurity density, said second-
conduction-type well being formed in said first-conduction-
type epitaxial region at a depth to reach said second-
conduction-type well relatively high in impurity density in
an area including said first region wherein the second
region extends substantially beyond an outer peripheral
portion of the first region,
2
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