Abstract: A variable-regeneration directional control valve for construction vehicles is disclosed. The control valve has a pressure control means for controlling the opposite pressure caused by elasticity of a valve spring. The opposite pressure acts on one end of a regeneration switching spool, while a self pressure (hydraulic pressure of pressurized fluid output from a pump) acts on the other end of the regeneration switching spool and thereby moves the spool. In the preferred embodiment, the means is a pressure control piston, which is provided on the end of the valve spring. The pressure control piston receives an outside control signal through an electronic proportional control valve and thereby continuously moves. The electronic proportional control valve outputs pressurized fluid in proportion to a current amount of the outside control signal.

Abstract: A return fluid regeneration device for construction vehicles is provided. The regeneration device includes an orifice disposed on a return-side internal line of a directional control valve of an actuator. A regeneration line is arranged between the return-side internal line and a return line extending to a return tank and is further selectively connected to the return-side internal line during a weight operation of the actuator. A regeneration branch line is branched from the return-side internal line and is connected to a supply-side internal line of the valve, thus selectively feeding the return fluid from the return-side internal line to the supply-side internal line and thereby regenerating the return fluid. First and second check valve are also provided on the regeneration line and branch line, respectively. The regeneration device regulates the moving speed of the actuator while simultaneously preventing the generation of high pressure in a fluid supply line.

Abstract: A semiconductor memory device includes a plurality of memory cells each having a single transistor and a single capacitor on a semiconductor substrate. The capacitor has a storage electrode with an externally communicated box-type tunnel in its center, one portion of the storage electrode being connected to the source region of the transistor. A method for manufacturing the semiconductor memory device is also provided. Thus, storage capacity is raised by increasing the effective area of the capacitor, and the planarizing effect is also excellent.

Abstract: A device isolation method for use in a process for manufacturing a semiconductor device, in which a pad oxide layer and a nitride layer are sequentially formed on the surface of a semiconductor substrate, an opening for defining the device isolating region is formed, and the substrate is oxidized at a high temperature to form a field oxide layer. Before the field oxide layer is formed, the nitride layer and pad oxide layer are etched to form a nitride layer spacer on the sidewalls of the pad oxide layer, to suppress the creation of a bird's beak due to lateral diffusion of oxygen between the pad oxide layer and nitride layer. In one embodiment, the nitride layer spacer is formed while leaving part of the pad oxide layer on the substrate, and the lower periphery of the spacer is undercut to be filled with an oxidizable material, thereby minimizing lateral diffusion of oxygen during the oxidation step.