The continuous innovation of captivating new organic semiconducting materials remains pivotal in the development of high‐performance organic electronic devices. Herein, a molecular engineering by combining sila‐annulation with the vertical extension of rylene diimides (RDIs) toward high‐mobility organic semiconductors is presented. The unilateral and bilateral sila‐annulated quaterrylene diimides (Si‐QDI and 2Si‐QDI) are designed and synthesized. In particular, the symmetrical bilateral 2Si‐QDI exhibits a compact, 1D slipped π–π stacking arrangement through the synergistic combination of a sizable π‐conjugated core and intercalating alkyl chains. Combining the appreciable elevated HOMO levels and reduced energy gaps, the single‐crystalline organic field‐effect transistors (SC‐OFETs) based on 2Si‐QDI demonstrate exceptional ambipolar transport characteristics with an impressive hole mobility of 3.0 cm2 V−1 s−1 and an electron mobility of 0.03 cm2 V−1 s−1, representing the best ampibolar SC‐OFETs based on RDIs. Detailed theoretical calculations rationalize that the larger transfer integral along the π–π stacking direction is responsible for the achievement of the superior charge transport. This study showcases the remarkable potential of sila‐annulation in optimizing carrier transport performances of polycyclic aromatic hydrocarbons (PAHs). A molecular engineering toward high‐mobility organic semiconductors by combining sila‐annulation with the vertical extension of rylene diimides is presented. The resultant 2Si‐QDI exhibits tunable energy levels and packing arrangement. The single‐crystalline organic field‐effect transistors demonstrate exceptional ambipolar transport characteristics with an impressive hole mobility of 3.0 cm2 V−1 s−1 and an electron mobility of 0.03 cm2 V−1 s−1.