Compared with a control Si p-channel, a compressive SiGe p-channel degrades as the width-to-length (W/L) ratio increases beyond a critical value. This ratio varies at different areas of a wafer. The threshold voltage and transconductance differences between a strained SiGe and a control Si p-channel augment as the W/L ratio increases. However, the transconductance difference in an n-channel diminishes as the ratio increases, which can be explained by the prominent longitudinal or transverse configuration of the piezoresistance coefficients of [110] SiGe. The interfacial stress between a capsulated Si and SiGe can be approximated by comparing the degradations of a strained SiGe and that of a control Si channel. (C) 2014 Elsevier Ltd. All rights reserved.