Semiconductor device and methods for forming the same

A semiconductor device, comprising:

• a substrate having a first conductivity type;
• an epitaxial layer on the substrate, wherein the epitaxial layer has the first conductivity type;
• a well region over the substrate, wherein the well region is formed in the epitaxial layer and has a second conductivity type;
• an insulating pillar extending into the epitaxial layer;
• at least one first doping region in the epitaxial layer, wherein the at least one first doping region has the second conductivity type and surrounds sidewalls of the insulating pillar, and the insulating pillar penetrates the at least one first doping region by extending from a top portion of the at least one first doping region to a bottom portion of the at least one first doping region, and the at least one first doping region is electrically connected to the well region;
• at least one second doping region having the second conductivity type, wherein the at least one second doping region is positioned under the at least one first doping region and closer to the substrate than the at least one first doping region;
• and
• a gate structure disposed at one lateral side of the insulating pillar, wherein the gate structure extends into the epitaxial layer and is separated from the insulating pillar;
• wherein the at least one second doping region is disposed under the insulating pillar, and the at least one second doping region and the insulating pillar are separated from each other by a distance.