To investigate and understand the reliability behavior of strained silicon devices, the changes of gate currents (I g) and substrate currents (I sub) in n and p-channel metal-oxide-semiconductor field-transistors (MOSFETs) under different types of mechanically applied tensile stresses have been studied. It has been observed that, under the uniaxial tensile stress, both I g and I sub of pMOSFETs increase with the increase of applied stress under the inversion and the accumulation conditions. However, an opposite stress dependence in nMOSFETs has been observed for I g and I sub in both the inversion and the accumulation regimes. Similar changes have been found for I g and I sub of nMOSFETs under biaxial tensile stress. The observations are explained by the strain induced band structure modulation and the repopulation of carriers. © 2012 American Institute of Physics.