SEMICONDUCTOR DEVICE

PURPOSE:To obtain the title device wherein dislocation caused by the mismatching of crystal lattice scarcely generates in a hetero junction and in its vicinity, and the hetero junction can sufficiently exhibit expected characteristics, by constituting a second semiconductor layer of crystal silicon containing element having bonding energy to Si larger than the mutual bonding energy of Si and impurity imparting a conductivity type. CONSTITUTION:On a first semiconductor layer of single crystal Si or on a semiconductor substrate 1, a second semiconductor layer 2 is formed; the layer 2 is composed of crystal Si containing element having bonding energy to Si larger than the mutual bonding energy of Si and impurity imparting a conductivity type. A surface 3 of the second semiconductor layer 2 is in contact with a first semiconductor layer or the semiconductor substrate 1; a depletion layer having a thickness of D stretches in the second semiconductor 2 from the surface 3; the diffusion length of minority carrier in the second semiconductor layer 2 is L; in a region 4 being the sum of L and D, the above mentioned element has the following concentration distribution; as a position approaches the opposite side of the first semiconductor layer or the semiconductor substrate 1 from the above surface 3, the concentration increases up to a desired value Na or a value Na' which is higher than Na but approximate to Na.