Recent rapid advances in atomic-scale crystal growth and nanofabrication techniques have enabled researchers to realise various kinds of three-dimensional (3D) electron confinement in semiconductors. This paper presents a numerical simulation for quantum-dot-based electronic devices. The electronic structures calculations of a CdS/SiO 2 quantum dot have been have been performed based on the resolution of the three-dimensional time-independent Schr ödinger equation in the effective mass theory (EMT) and the band parabolicity approximation. The influence of the strain and dot separation on the formation of coupled quantum dot levels has been discussed. The oscillator strengths for intersubband electronic transitions have been also calculated. Besides, it is found that the subband energies and intersubband optical absorption are rather sensitive to the applied electric field. This gives a further parameter in various device applications based on the intersubband transitions. We hope that the present results may make a contribution to experimental studies of CdS/SiO 2 quantum dot based structures which can be produced by inexpensive means. Our calculations provide good guidance for the selection of dot parameters to obtain absorption in quantum dot infrared photodetectors and a better understanding of the intersubband transition phenomena in quantum dot.