Dynamic random access memory device

A dynamic random access memory (DRAM) device, comprising:

• a plurality of word lines, disposed in a substrate along a first trench extending along a first direction, each of the word lines comprising a multi-composition barrier layer, wherein the multi-composition barrier layer comprises TiSixNy with x and y being greater than 0, and the multi-composition barrier layer is silicon-rich at a bottom portion thereof and is nitrogen-rich at a top portion thereof, wherein x gradually decreases from 20 to 0.1 from the bottom to the top of the multi-composition barrier layer, and y gradually increases from 0.1 to 20 from the bottom to the top of the multi-composition barrier layer;
• and
• a plurality of bit lines disposed over the word lines and extending along a second direction across the first direction.