The disclosed technology relates to transistors having a strained quantum well for carrier confinement, and a method for manufacturing thereof. In one aspect, a FinFET or a planar FET device comprises a semiconductor substrate, a strain-relaxed buffer layer comprising Ge formed on the semiconductor substrate, a channel layer formed on the strain-relaxed buffer layer, and a strained quantum barrier layer comprising SiGe interposed between and in contact with the strain-relaxed buffer layer and the channel layer. The compositions of the strain-relaxed buffer layer, the strained quantum barrier layer and the channel layer are chosen such that a band offset of the channel layer and a band offset of the strained quantum barrier layer have opposite signs with respect to the strain-relaxed buffer layer.