| 摘要 |
PROBLEM TO BE SOLVED: To reduce through-dislocation density and reduce surface roughness to a practical level in a semiconductor substrate, a field effect transistor, and a method of manufacturing these. SOLUTION: The field effect transistor comprises an Si substrate 1, a first SiGe layer 2 formed on the Si substrate, and a second SiGe layer 3 formed directly on the first SiGe layer or via an Si layer. The first SiGe layer is formed in a thickness which is thinner than twice the critical thickness, at which dislocation is generated, due to increase in the thickness and thereby lattice relaxation occurs, and the second SiGe layer has a mole fraction of Ge which is lower than the maximum value of the mole fraction of Ge in the first SiGe layer, at least in a contact face with first SiGe layer or the Si layer, and also includes a tilted mole fraction region where the mole fraction of Ge increases gradually toward the surface, in at least a part of it.
|
