Patent ID: 7391077

Claim:
A semiconductor device, comprising: a semiconductor substrate comprising a first semiconductor layer of a first conductivity and a pair of second semiconductor layers disposed on the first semiconductor layer and spaced apart from each other, the second semiconductor layers forming a trench therebetween and the first semiconductor layer forming a bottom surface of the trench, wherein each of the second semiconductor layers includes a first impurity diffused region of the first conductivity which extends from a lower surface toward an upper surface of the second semiconductor layer, and a second impurity diffused region of a second conductivity which extends from the lower surface toward the upper surface and is adjacent to the first impurity diffused region, the first and second impurity diffused regions being in contact with the first semiconductor layer; an insulating layer covering a sidewall of the trench, wherein the insulating layer covers the whole surface of the sidewall of the trench; and a cap layer which is in contact with the semiconductor substrate and covers an opening of the trench to form an enclosed space in the trench, a material of the cap layer being substantially the same as a material of the semiconductor substrate.