This paper propose the density-rule aware library design. Model equation is used to estimate the impact of density rule in cell level design. Three types of layout style is evaluated in cell level and circuit level design. Comparison result shows I-shape library achieves 19.1% area reduction at the cost of 1.7% energy overhead, compare to single contact Z-shape library. Double contact Z-shape library reduces this area overhead to 18.9% adding contact and diffusion layers in source node.