In order to improve p-type resonant tunneling diodes (RTD) with Si/strained Si(0.8)Ge(0.2) heterostructures epitaxially grown on Si(100), effectiveness of Ge fraction modulation in the quantum well and a part of spacers was investigated. It was found that increase of the Ge fraction up to x=0.30-0.42 effectively improves RTD characteristics even at high temperatures around 200 K (C) 2008 Elsevier B.V. All rights reserved.