| 摘要 |
<p>A double epilayer substrate or wafer is used as starting material for integrated circuit technologies, such as CMOS technologies designed for n-type substrates. The double epilayer substrate comprises an n-type top epitaxial layer (301), a thinner buried n-type epitaxial layer (302) having a higher dopant concentration than said top epitaxial layer, and a p-type substrate (303). A varactor is processed inside an n-type pocket or well (300) defined by deep p-type guard rings (304) diffused to form an ohmic contact with the p-type substrate. This deep guard ring (304) isolates the varactor from the surrounding intergrated circuit chip. <IMAGE></p> |
