Patent ID: 9312258
Filing Date: 2016-04-12
CPC Classification: H01L

Claim Text:
1. A strained silicon structure comprising: a substrate having a top surface, wherein the substrate is defined into a low density region and a high density region; a first transistor disposed on the top surface and within the low density region; and a second transistor disposed on the top surface and within the high density region, wherein a cross-sectional profile of a first source/drain region of the first transistor is different from a cross-sectional profile of a second source/drain region of the second transistor, wherein the first transistor and the second transistor have a same conductivity type and wherein the first source/drain region comprises a first recess disposed in the substrate and a first epitaxial layer filling the first recess, the second source/drain region comprises a second recess disposed in the substrate and a second epitaxial layer filling the second recess.