Substantial improvement of electrical and optical properties of InGaN/GaN multiple quantum wells (MQWs) was obtained with a triangular band structure. Transmission electron microscopy (TEM) images from the triangular MQWs showed the formation of uniformly and densely distributed quantum dots having diameters of 20-50 nm. The light-emitting diodes (LEDs) with the triangular QWs showed a lower operation voltage, a higher light output power, and higher intensities and narrower line widths of electroluminescence spectra than those with the rectangular QWs. Very bright and uniform light emission from the triangular MQW LEDs was also observed at a low injection current, but spatially non-uniform emission from the rectangular ones.