To achieve high coding performance for screen content, the intra block copy (IntraBC) performs block matching within a limited area of the reconstructed samples inside the current picture. We further extend its notion from the unit of square coding unit (CU) to non-square prediction unit (PU) partitions. This design is then justified by theoretical and empirical analyses which reveal the same fact that blocks coded by IntraBC mode tend to enable more at smaller partition levels. Besides, the syntax design of the proposed method is fully aligned with that of inter partition modes. Therefore the architecture-wise change in video codec design can be minimized. The experimental results justify the effectiveness of the proposed mode for coding of screen content video. In particular, up to 19.5% rate reduction (with an average of 12.7%) relative to the HM-12.0+RExt-4.1 anchor can be achieved on top of the usage of CU-based IntraBC prediction.