Two dimensional (2D) semiconductors such as MoS2 and WSe2 have attracted attention for various optoelectronic and electronic applications owing to their good optical, electrical and mechanical properties. However, the lack of efficient methods for their production at levels of quality, uniformity, and reliability needed for practical applications restricts the applicability of 2D semiconductors to optoelectronics and electronics. In this talk, as an alternative 2D semiconductor, I present single-crystal Si nanomembranes (NMs), with precisely defined thicknesses ranging from 1.4 to 10 nm. The Si NMs exhibit high optical transparency, low flexural rigidity and distinctive electrical properties. Deterministic assembly techniques allow integration of this Si NMs into unusual device architectures, including transistors and logic circuits for potential use in transparent and flexible forms of electronics. In addition, I report a new strain engineering approach to induce a tensile strain to the Si NMs, exhibiting a mobility enhancement factor of 1.2−1.4 compared with an unstrained Si TFT without using an additional epitaxial stressor layer.