This paper reports our recent results on a new method for controlling the internal strain and Light emission in Si-Si1-xGex quantum dots (QD) by coating a special SiNx layer with controlled built-in stress. It was found that by changing the stress in the coating layer, a systematic change of photoluminescence intensity and peak position has been observed. An optimum experimental regime was found where improved light emission remains after the SiNx coating, This provides a general way of preparing a stable dielectric film suitable for and controlling the internal strain in the QD diodes and other structures.