The invention provides a DRAM device and a manufacturing method thereof. The manufacturing method of the DRAM device comprises steps that, a substrate is provided; a first grid electrode and a second grid electrode are formed; source electrodes or drain electrodes of a logic transistor and a channel transistor are formed, a dielectric layer and a metal layer are formed, and the dielectric layer and the source electrode or the drain electrode of the channel transistor commonly form a capacitor. The DRAM device comprises the substrate, the channel transistor, the capacitor and the logic transistor, wherein the dielectric layer and the metal layer are sequentially arranged on the source electrode or the drain electrode of the transistor, and the source electrode or the drain electrode, the dielectric layer and the metal layer are used for forming the capacitor. The method and the device are advantaged in that, the dielectric layer and the metal layer are formed on the source electrode or the drain electrode of the channel transistor for forming the capacitor, a problem that a special deep trench for forming a capacitor is formed in a substrate in the prior art can be solved, the manufacturing process is simplified, manufacturing complexity is reduced, and compatibility with the routine manufacturing flow can be better.