This work discusses the design methods of 120 GHz on-chip dual-mode and three-mode dielectric resonator antennas (DRAs) based on a standard CMOS technology. The bandwidths of the DRAs are expanded by merging adjacent modes with similar radiation patterns. The impedance bandwidth of 18.6% with the peak gain of 6 dBi is achieved for the proposed on-chip dual-mode DRA. In addition, the impedance bandwidth of 20.1% with the peak gain of 6.9 dBi is achieved for the proposed three-mode DRA. To the best of authors’ knowledge, the on-chip multi-mode DRAs are first proposed. The impedance bandwidth of the proposed three-mode on-chip DRA is wider than the other on-chip DRAs using planar feeding with on-chip ground. The proposed antennas are promising for terahertz applications due to the merits of wide band, high gain and high radiation efficiency.