Current status and critical issues of the material and device technology towards constructing new architecture LSIs based on quantum-mechanical principles are reviewed in an attempt to draw attention of systems workers to the field. Limitations of the present-day LSI architecture are discussed from the viewpoints of material science and device physics. New quantum mechanical phenomena in the quantum structures are reviewed. Then, key material and processing issues for fabrication of desired quantum structures are briefly discussed. Finally, the basic operation principles the quantum devices and possible architectures of quantum LSIs are discussed.