This paper presents an original design for dual-band dual-mode bandpass filter based on a single grounded patch resonator. It is implemented on BiCMOS 55 nm technology to operate at 180 GHz and 270 GHz. A full control of both bands is possible — thanks to the usage of vias and slots. The grounded vias significantly allow the reduction of the patch resonator realizing an overall size of 0.04 mm², which is a fundamental aspect for (Bi)CMOS. The achieved results show a good agreement between simulation and measurement results with insertion loss of 4–5 dB in the passband, return loss of 14 dB and relative bandwidths of about 18%.