Atomically controlled formation of strained Si 1-xGe x/Si quantum heterostructure was investigated in order to improve negative differential conductance (NDC) characteristics of high-Ge-fraction strained Si 1-xGe x/Si hole resonant tunneling diode with nanometer-order thick strained Si 1-xGe x and unstrained Si layers. Recently, especially to suppress the roughness generation at heterointerfaces for higher Ge fraction, Si barriers were deposited using Si 2H 6 reaction at a lower temperature of 400 °C instead of SiH 4 reaction at 500 °C after the Si 0.42Ge 0.58 growth. NDC characteristics show that difference between peak and valley currents is effectively enhanced at 11-295 K by using Si 2H 6 at 400 °C, compared with that using SiH 4 at 500 °C. Thermionic-emission dominant characteristics suggests a possibility that introduction of larger barrier height enhances the NDC at room temperature by suppression of thermionic-emission current. In this paper, based on our results, advanced epitaxial growth process of RTDs with atomically controlled Si/strained Si 1-xGe x heterostructures on Si(100) are reviewed.