Semiconductor device having bottom bit line and narrow channel, and forming method thereof

Abstract

The present disclosure relates to the technical field of semiconductor manufacturing, and in particular to a semiconductor device and a forming method thereof. The forming method of a semiconductor device includes: providing a substrate; etching the substrate to form first recesses and second recesses located below the first recesses and communicating with the first recesses; forming a bit line in the second recesses; forming, at bottoms of the first recesses, an isolation layer covering the bit line; enlarging an inner diameter of the first recess above the isolation layer; and forming a gate layer on a sidewall of the first recess whose inner diameter is enlarged.