Abstract: The invention provides a trench gate type transistor in which the gate capacitance is reduced, the crystal defect is prevented and the gate breakdown voltage is enhanced. Trenches are formed in an N? type semiconductor layer. A uniformly thick silicon oxide film is formed on the bottom of each of the trenches and near the bottom, being round at corner portions. A silicon oxide film is formed on the upper portion of the sidewall of each of the trenches, which is thinner than the silicon oxide film and round at corner portions. Gate electrodes are formed from inside the trenches onto the outside thereof. The thick silicon oxide film reduces the gate capacitance, and the thin silicon oxide film on the upper portion provides good transistor characteristics. Furthermore, with the round corner portions, the crystal defect does not easily occur, and the gate electric field is dispersed to enhance the gate breakdown voltage.

Abstract: A semiconductor device that reduces the width of an isolation region between semiconductor elements. The semiconductor device includes a semiconductor substrate, an epitaxial layer formed on the semiconductor substrate, a buried layer formed between the semiconductor substrate and the epitaxial layer, a first trench formed in the epitaxial layer so as to surround the buried layer, and an insulation film formed in the first trench.

Abstract: A semiconductor device that reduces the interval between gate electrodes. The semiconductor device includes a semiconductor substrate, a plurality of gate electrodes buried in the semiconductor substrate, a plurality of first insulation layers arranged respectively on the plurality of gate electrodes, a conductive layer formed on the surface of the semiconductor substrate near the plurality of gate electrodes and the plurality of first insulation layers, and a conductor layer arranged on at least the conductive layer.

Abstract: A semiconductor device that reduces the width of an isolation region between semiconductor elements. The semiconductor device includes a semiconductor substrate, an epitaxial layer formed on the semiconductor substrate, a buried layer formed between the semiconductor substrate and the epitaxial layer, a first trench formed in the epitaxial layer so as to surround the buried layer, and an insulation film formed in the first trench.