The present invention proposes a method of manufacturing a semiconductor device, which includes the steps of providing a substrate with a memory region and a logic region, forming bit lines and logic gates respectively in the memory region and the logic region, wherein storage node regions are defined between bit lines, forming a first low-K dielectric layer on sidewalls of bit lines, forming a doped silicon layer in the storage node regions between bit lines, wherein the top surface of doped silicon layer is lower than the top surface of bit line, forming a second low-K dielectric layer on sidewalls of storage node regions, and filling up storage node regions with metal plugs.