| 摘要 |
PURPOSE:To raise the P-N junction breakdown strength and to decrease the deterioration of element properties by providing a region which is of the same conductivity as a semiconductor substrate and is lower in impurity concentration than a punch through preventive layer, at, at least, a groove bottom part. CONSTITUTION:A capacity insulating film 4 exists over the whole area at the surface of a groove for a groove capacitor, and inside the groove exists a capacity electrode 6 consisting of polycrystalline silicon, or the like, and outside it exists a semiconductor layer, having reverse conductivity to a semiconductor substrate, as a charge accumulating layer 2. The part, which forms an angle of 45 deg. with the main surface of the semiconductor substrate 1, has the same conductivity as the semiconductor substrate 1, and then a punch through preventive layer 3, Which has higher impurity concentration, is made, and P-N junction is made between it and the semiconductor substrate 1. Moreover, the part, which forms an angle below 45 deg. with the main surface, is covered with a medium concentration semiconductor layer 13, which has the same conductivity type and impurity concentration as the semiconductor substrate 1. Hereby, the preservation inferiority by the interference between adjacent accumulation nodes is prevented by the punch through preventive layer, and the effect to the property deterioration of an element decreases. |
