Patent ID: 9559187
Date: 2017-01-31
CPC Classifications: H01L

Claim:
1. A method for fabricating a semiconductor device, comprising: ion-implanting an impurity into a substrate; forming a first epitaxial layer over the substrate and a first buried impurity region between the first epitaxial layer and the substrate by activating the impurity ion-implanted into the substrate; ion-implanting an impurity into the first epitaxial layer at a border contacting the first buried impurity region; forming a second epitaxial layer over the first epitaxial layer and a second buried impurity region, which contacts the first buried impurity region, between the second epitaxial layer and the first epitaxial layer by activating the impurity ion-implanted into the first epitaxial layer; and forming a deep well that contacts the second buried impurity region in the second epitaxial layer, wherein the first epitaxial layer has a higher impurity doping concentration than that of the second epitaxial layer.