| 摘要 |
PROBLEM TO BE SOLVED: To overcome the problem of a prior art such that a high temperature and long time heat treatment is needed to form a deep well for forming a high breakdown voltage CMOS transistor but cannot be applied to a large-area substrate, or for forming a well by a high energy ion implantation, the well depth is determined, depending on a device, this making difficult forming a well of desired depth. SOLUTION: A first and second epitaxial layers 2, 3 are formed and used as wells on a substrate 1. The use of the epitaxial layers 2, 3 as wells eliminates the need of a high temperature and long time heat treatment and the depth of the well is not limited by a high energy ion implanting apparatus but wells of a desired and uniform concentration can be obtained.
|
