Results obtained by an advanced growth of site-controlled quantum dots (SCQDs) on pre-patterned nanoholes and their integration into both photonic resonators and nanoelectronic memories are summarized. A specific technique has been pursued to improve the optical quality of single SCQDs. Quantum dot (QD) layers have been vertically stacked but spectrally detuned for single SCQD studies. Thereby, the average emission linewidth of single QDs could be reduced from 2.3 meV for SCQDs in a first QD layer close to the etched nanoholes down to 600 microeV in the third InAs QD layer. Accurate SCQD nucleation on large QD distances is maintained by vertical strain induced QD coupling throughout the QD stacks. Record narrow linewidths of individual SCQDs down to approximately 110 microeV have been obtained. Experiments performed on coupled photonic SCQD-resonator devices show an enhancement of spontaneous emission. SCQDs have also been integrated deterministically in high electron mobility heterostructures and flash memory operation at room temperature has been observed.