Semiconductor device and method of forming thereof

A semiconductor device, comprising:

• a substrate including a cell area and a peripheral area;
• an isolating trench defining a cell active area in the cell area, and a peripheral active area in the peripheral area;
• a cell gate structure formed in the cell active area and crossing the isolating trench;
• a first protection layer formed on an upper surface of the cell active area, and an inner wall and bottom of the isolating trench;
• a second protection layer formed on the first protection layer on the upper surface of the cell active area and the bottom of the isolating trench;
• a bit line structure arranged substantially perpendicular to the cell gate structure, and crossing the cell active area;
• and
• a peripheral gate line structure crossing the peripheral active area.