In this paper, we discuss new reliability issues for manufacturing deep-submicron semiconductor devices; mechanical reliability issues which cause serious damages in semiconductor devices. Typical damages are dislocations in silicon substrates, delamination or cracking of thin films, and deterioration of electronic characteristics of devices. Mechanical stress develops in device structures due to not only mismatches in thermal expansion coefficients among thin film materials but also intrinsic stress of thin films such as poly-silicon and silicides. Fine patterning by dry etching makes sharp edges which also cause high stress due to stress concentration. The main manufacturing processes at which stress mainly develops are isolation, gate formation, and interconnect formation. We review each process for highly reliable manufacturing. Finally we mention the effect of residual stress in transistor areas on the shift in the electronic characteristic of MOS transistors.