Three-dimensional memory device having contact via structures in overlapped terrace region and method of making thereof

A three-dimensional memory device comprising:

• a first tier structure including a first alternating stack of first insulating layers and first electrically conductive layers that is located over a top surface of a substrate and having a first terrace region containing first steps;
• a second tier structure including a second alternating stack of second insulating layers and second electrically conductive layers that overlies the first tier structure and having a second terrace region containing second steps that overlies the first steps in the first terrace region;
• a memory array region located adjacent to the first terrace region and the second terrace region and including memory stack structures that extend through the first alternating stack and the second alternating stack, wherein each of the memory stack structures comprises a memory film and a vertical channel;
• and
• first contact via structures vertically extending through the second tier structure in the second terrace region and extending into the first tier structure in the first terrace region and contacting a respective one of the first electrically conductive layers.