The advance of Nano Science and Technology in recent years has helped create unprecedented opportunities to design and engineer structures at the quantum scale to realize novel material functionalities. As an example, advanced materials synthesis techniques such as molecular beam epitaxy (MBE) have enabled artificial engineering of low dimensional electronic systems that led to the discovery of many novel scientific phenomena as well as new technologies. To date most artificially engineered materials are either all semiconductor based or all metal based. Recent research efforts, however, have led to significant advancements in MBE growth of metals on semiconductors. In particular, the so called “quantum growth” or “electronic growth” mechanism, has led to unprecedented control of pristine metallic films on semiconductor substrates. This talk will focus on applications of such quantum control of metal/semiconductor heterostructures in two areas: (a) superconductivity of metallic thin films nanostructures; and (b) nanoscale optoelectronic properties of ultra-smooth metallic thin films. More specifically, in the first area, I will discuss how quantum control of the boundary condition impacts (i) shape resonance and robustness of thin film superconductivity and (ii) proximity/inverse proximity effects of lateral and vertical superconductor/normal metal heterojunctions. In the second area, I will discuss a new class of optoelectronic devices enabled by confined surface plasmon polariton cavity mode, more specifically, the demonstration of the first low threshold, continuous wave operation of plasmonic nanolaser with physical size much smaller than the diffraction limits.