Methods of manufacturing semiconductor devices with local recess channel transistors

A method of manufacturing a local recess channel transistor in a semiconductor device, the method comprising:

• forming a local channel impurity doped region in a semiconductor substrate by doping the substrate with a channel impurity;
• forming a recess trench in the substrate that exposes a portion of the local channel impurity doped region;
• forming a threshold voltage (Vth) adjusting impurity doped region inside the local channel impurity doped region by doping a portion of the substrate along a bottom portion of the recess trench with a threshold voltage impurity;
• forming a gate insulating layer on the substrate in the recess trench;
• forming a gate electrode layer on the gate insulating layer in the recess trench;
• and
• forming a gate from the gate insulating layer and the gate electrode layer,
• wherein forming a local channel impurity doped region comprises:
• forming a buffer layer on the substrate;
• forming a hard mask layer on the buffer layer;
• forming a photoresist layer on the hard mask layer;
• patterning the photoresist layer to form a photoresist layer pattern that exposes a portion of the hard mask layer;
• etching the hard mask layer using the photoresist layer pattern as an etch mask to expose a portion of the buffer layer;
• and
• ion-implanting a channel impurity through the exposed portion of the buffer layer using the photoresist layer pattern as an ion-implantation mask to form the local channel impurity doped region.

A method of manufacturing a local recess channel transistor in a semiconductor device, the method comprising:

• forming a hard mask layer on a semiconductor substrate that exposes a portion of the substrate;
• etching the exposed portion of the substrate using the hard mask layer as an etch mask to form a recess trench;
• forming a trench spacer on the substrate along a portion of sidewalls of the recess trench, wherein the substrate along a lower portion of the recess trench is exposed after the trench spacer is formed;
• doping the exposed portion of the substrate along the lower portion of the recess trench with a channel impurity to form a local channel impurity doped region surrounding the lower portion of the recess trench;
• doping a portion of the local channel impurity doped region surrounding the lower portion of the recess trench with a threshold voltage (Vth) adjusting impurity to form a Vth adjusting impurity doped region inside the local channel impurity doped region;
• expanding width of the lower portion of the recess trench;
• forming a gate insulating layer on the substrate in the recess trench;
• forming a gate electrode layer on the gate insulating layer in the recess trench;
• and
• etching a portion of the gate insulating layer and the gate electrode layer to form a gate.