Patent ID: 9697901
Date: 2017-07-04
CPC Classifications: G11C

Claim:
1. A three-dimensional (3D) flash memory device having a plurality of cell strings arranged in a direction perpendicular to a substrate, the 3D flash memory comprising: a first cell string connected between a common source line and a bit line, and including a first ground select transistor, a first plurality of memory cells and a first string select transistor, wherein the first ground select transistor, the first plurality of memory cells and the first string select transistor are coupled to a ground select line, a plurality of main word lines, and a first string select line respectively, and the first ground select transistor is adjacent to the substrate and the first string select transistor is adjacent to the bit line; a first dummy word line disposed between the ground select line and the plurality of main word lines and adjacent to lowermost word line of the plurality of main word lines; and a second dummy word line disposed between the first string select line and the plurality of main word lines and adjacent to uppermost word line of the plurality of main word lines, wherein a first separation length between the ground select line and the first dummy word line is different from a second separation length between the first string select line and the second dummy word line.