This book constitutes selected papers from the Second International Conference on Microelectronic Devices, Circuits and Systems, ICMDCS 2021, held in Vellore, India, in February 2021. The 32 full papers and 6 short papers presented were thoroughly reviewed and selected from 103 submissions. They are organized in the topical sections on digital design for signal, image and video processing; VLSI testing and verification; emerging technologies and IoT; nano-scale modelling and process technology device; analog and mixed signal design; communication technologies and circuits; technology and modelling for micro electronic devices; electronics for green technology.