Modern high speed (RF) transistors encounter certain delay while operated at high frequency or under fast transient condition. This effect is named as Non Quasi Static (NQS) effect. In this work, NQS effect is analyzed in a concise manner so that it can be readily implemented in a compact model using the VerilogA description language. The basic physics behind this effect is investigated in small signal domain and results are compared with the published work. Compact modeling with HICUM model is performed with both measured and device simulated data. At last, an improved excess phase circuit is proposed to model the NQS effect.