Various embodiments of the present application are directed to an IC, and associated forming methods. In some embodiments, the IC comprises a memory region and a logic region integrated in a substrate. A plurality of memory cell structures is disposed on the memory region. A plurality of logic devices is disposed on the logic region. A sidewall spacer is disposed along a sidewall surface of the logic devices, but not disposed along a sidewall surface of the memory cell structures. Thus, the inter-layer dielectric (ILD) fill-in window between adjacent memory cell structures is enlarged, compared to the approaches where the sidewall spacer is concurrently formed in both memory region and the logic region. Thereby, voids formation would be reduced or eliminated, and device quality would be improved.