Abstract: In high-voltage devices comprising a lightly doped region (3) provided with a heavily doped contact zone 4, damage caused by local breakdown at the corner of the contact zone may occur as a result of the Kirk effect at a high current density. To improve the robustness of the device, an annular protection zone (14) of the same conductivity type is provided so as to surround the contact zone at a small distance. As a result, breakdown will occur initially at the corner of the protection zone. However, due to the resistance between the protection zone and the contact zone, a more uniform current distribution is obtained, which prevents damage caused by local current concentration.

Abstract: An access transistor (140) for a vertical DRAM device (110) and method of forming thereof. Trenches (114) are formed in a semiconductor wafer substrate (112), and storage capacitors (118) are formed in the bottom portion of the trenches (114). The trenches (114) are curved in a channel (130) region formed in a top portion of the trenches (114). The channel (130) is curved about a central point c, and the channel extends into the substrate (112) by a distance d along a radius b. A gate oxide (126) is disposed adjacent the curved channel (130), and a gate conductor (128) is disposed adjacent the gate oxide (126).

Abstract: A DRAM cell with a vertical transistor forms a buried strap outdiffusion with reduced lateral extent by shifting high temperature steps that affect the thermal budget before the initial buried strap diffusion. The gate conductor is formed in two steps, with poly sidewalls being put down above a sacrificial Trench top oxide to form a self-aligned poly-gate insulator structure before the formation of the LDD extension.

Abstract: An access transistor (140) for a vertical DRAM device (110) and method of forming thereof. Trenches (114) are formed in a semiconductor wafer substrate (112), and storage capacitors (118) are formed in the bottom portion of the trenches (114). The trenches (114) are curved in a channel (130) region formed in a top portion of the trenches (114). The channel (130) is curved about a central point c, and the channel extends into the substrate 212 by a distance d along a radius b. A gate oxide (126) is disposed adjacent the curved channel (130), and a gate conductor (128) is disposed adjacent the gate oxide (126).

Abstract: The invention relates to an optical unit (17) for synchronizing clock signals. The unit (17) comprises at least two ring lasers (1', 1"), each ring laser (1', 1") generating a repetitive optical pattern at a different repetition frequency f.sub.i. The repetition frequency of at least one of the ring lasers (1', 1") is variable. The unit (17) comprises detection means (19) adapted to simultaneously receive the optical patterns from two ring lasers (1', 1") to be synchronized with each other and to compare these patterns. The ring laser, whose repetition frequency is variable, is controllable on the basis of a signal from the detection means, by which the optical path length of this laser is changed. The invention also relates to a high-frequency carrier transmission system comprising an optical unit as described hereinbefore.

Abstract: An optical unit for multiplying the frequency of a clock signal includes at least two series-arranged ring lasers. Each ring laser has a different resonance frequency f.sub.i. The unit has an input for receiving a signal, for example, a low-frequency electric signal for modulating one of the ring lasers. The repetition frequency of at least one of the ring lasers is variable by adapting the optical path length of the resonator.

Abstract: A passive region is provided adjacent the mirror surface of a laser. A mesa is formed with an end face parallel to the mirror surface to be formed. The passive region is grown against the end face, and the mirror surface is formed therein by cleaving. The passive region is provided exclusively at the area of the active region. The passive region is provided at the area of the active region preferably in the following manner: two depressions are formed in the layer structure of the laser at the area of the mirror surface to be formed, reaching down to the active layer. Then a portion of the active layer situated between the depressions is selectively removed, whereupon the passive region is grown starting from the depressions in the tubular cavity thus formed.

Abstract: A multimode imaging component provided with a rectangular waveguide (14') having two ends (15, 19) is described. To avoid unwanted reflections of radiation in the waveguide, the surfaces (17, 21) between the windows (16, 18, 20, 22) at the ends are provided with means for reducing reflection, for example, anti-reflection coatings (24, 25). When such a multimode imaging component is used as a coupler in a ring laser, the radiation spectrum of the ring laser will not comprise unwanted spectral components.

Abstract: A ring laser is described, which has a ring (1) in which laser radiation is generated. A coupler (4) couples a part of the radiation in the form of two waves (7,8) to two waveguides (5,6). A combiner (11) combines the two waves to an output wave (12) in an output waveguide (13). By providing a reflector (16) in the output waveguide, a part of the output wave is reflected to the ring via the combiner, the two waveguides and the coupler. The radiation waves travelling in the ring couple to the reflected wave and thereby acquire a well-defined phase difference. The resultant phase equality of the two waves (7,8) at the input of the combiner ensures that the powers of the waves are added in phase so that the ring laser supplies the maximum possible power.