| 摘要 |
PURPOSE: To provide a semiconductor device having vertical transistors wherein irregularity of characteristic is small, and its manufacturing method. CONSTITUTION: Trenches 20 reaching an N-type silicon substrate 11 are formed on a SOI substrate 10 wherein a P-type silicon layer 13 is formed on the substrate 11 via a silicon oxide film 12, and trench capacitors C are formed in lower parts of the trenches 20. The silicon oxide film 12 exposed on the upper trenches 20 of storage electrodes 22 of the capacitors C are etched, trench diameter enlarging parts 25 are formed, and buried straps 23 are buried in the parts 25 in such a manner that only lower surfaces of the straps 23 are in contact with the P-type silicon layer 13. Upper parts of the buried straps 23 are covered with cap insulating films 24, and the vertical transistors Q are formed on side surfaces of the upper trenches 20. Sources and drains of the transistors Q are constituted of N+ type diffusion layers 31 which are diffused upward from the buried straps 23 to the P-type silicon layer 13 and an N+ type diffusion layer 32 on an upper surface of the P-type silicon layer 13.
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