Three-dimensional memory device with separated source-side lines and method of making the same

A three-dimensional memory device, comprising:

• an alternating stack of insulating layers and electrically conductive layers located over a plurality of source layers, wherein the alternating stack is located between a pair of backside trench fill structures, wherein the electrically conductive layers comprise word lines and source-side select gate electrodes which are located between the plurality of source layers and the word lines in a vertical direction,
• source-side trenches extending through both the source-side select gate electrodes and the plurality of source layers, wherein the source-side trenches do not divide the word lines;
• groups of memory openings vertically extending through the alternating stack;
• and
• groups of memory opening fill structures located in the groups of memory openings, wherein each of the memory opening fill structures includes a respective vertical stack of memory elements, a respective vertical semiconductor channel having a first end that contacts a respective one of the plurality of source layers, and a respective drain region contacting a second end of the respective vertical semiconductor channel,
• wherein:
• the plurality of source layers are laterally spaced apart and electrically isolated from each other;
• and
• each group of memory opening fill structures contacts a respective one of the plurality of source layers.