Patent ID: 7208799

Claim:
A semiconductor device comprising: a semiconductor substrate; a first insulation layer formed on the semiconductor substrate; a semiconductor layer insulated from the semiconductor substrate by the insulation layer; a source region of a first conduction type and a drain region of the first conduction type formed in the semiconductor layer; a body region of a second conduction type formed in the semiconductor layer between the source region and the drain region, said body region being capable of storing data by accumulating or releasing electric charge; a second insulation layer formed on the body region; a word line formed on the second insulation layer and insulated from the body region by the second insulation layer; and a bit line electrically connected to the drain region, wherein in a cross-section of the semiconductor device taken in a direction extending along and approximately parallel to the word line, a length of a boundary between the body region and the first insulation layer is larger than a length of a boundary between the body region and the second insulation layer, and the body region has steps on sides of the body region, the sides facing toward a direction extending along and approximately parallel to the word line.