This paper presents a design perspective of 2 nd order patch-like grounded Complementary-Split-Ring-Resonator (CSRR) filter on BiCMOS 55-nm technology at 50 GHz. The advantage of using CSRR topology combined with grounded via allows a great reduction of the overall size to \boldsymbol{\lambda/7\times\lambda/13}\ \mathbf{mm}^{2} . General coupling matrix representation along with extracted external quality factor and resonators' pair coupling is conducted. The measured results show an insertion loss of 5 dB with a return loss better than 11 dB in the passband. The achieved fractional bandwidth is 23%.