A device capable of capturing and facilitating the removal of a thrombus in blood vessels (or stones in biliary or urinary ducts, or foreign bodies) uses a soft coil mesh with the aid of a pull wire or string to engage the surface of a thrombus, and remove the captured thrombus. The soft coil mesh is formed by an elongated microcoil element that forms the helical elements of a macrocoil element. The microcoil element provides a relatively elastic effect to the helical elements forming the macrocoil and allows for control of gripping forces on the thrombus while reducing non-rigid contact of the device with arterial walls. The use of multiple coil mesh elements, delivered through a single lumen or multiple lumens, preferably with separate control of at least one end of each coil, provides a firm grasp on a distal side of a thrombus, assisting in non-disruptive or minimally disrupted removal of the thrombus upon withdrawal of the device.

Thrombus removal system and process

Self-aligned trench MOSFETs and methods for manufacturing the same are disclosed. By having a self-aligned structure, the number of MOSFETS per unit area—the cell density—is increased, making the MOSFETs cheaper to produce. The self-aligned structure for the MOSFET is provided by making the sidewall of the overlying isolation dielectric layer substantially aligned with the sidewall of the gate conductor. Such an alignment can be made through any number of methods such as using a dual dielectric process, using a selective dielectric oxidation process, using a selective dielectric deposition process, or a spin-on-glass dielectric process.

Self-aligned trench mosfets and methods for making the same

An asymmetric insulated-gate field effect transistor (100U or 102U) is provided along an upper surface of a semiconductor body so as to have first and second source/drain zones (240 and 242 or 280 and 282) laterally separated by a channel zone (244 or 284) of the transistor's body material. A gate electrode (262 or 302) overlies a gate dielectric layer (260 or 300) above the channel zone. A pocket portion (250 or 290) of the body material more heavily doped than laterally adjacent material of the body material extends along largely only the first of the S/D zones and into the channel zone. The vertical dopant profile of the pocket portion is tailored to reach a plurality of local maxima at respective locations (PH-1-PH-3-NH-3) spaced apart from one another. This typically enables the transistor to have reduced current leakage.

Fabrication of semiconductor structure having asymmetric field-effect transistor with tailored pocket portion along source/drain zone

Impurity concentration (N d (X)) in an n-drift layer in a diode is at a maximum at a position at a distance Xp from an anode electrode in a direction from the anode electrode to a cathode electrode, and gradually decreases from the position toward each of the anode electrode and the cathode electrode. A ratio of the peak impurity concentration N p to an averaged impurity concentration N dm in the n-drift layer is in the range of 1 to 5. This provides a diode and a manufacturing method thereof by which oscillations in voltage and current at reverse recovery are inhibited to achieve enhancement both in high speed and low-loss characteristics and in soft recovery characteristics.

Power semiconductor rectifier having broad buffer structure

Power semiconductor rectifier having broad buffer structure and method of manufacturing thereof

An n- layer (2E) having a low impurity concentration is epitaxially grown on a surface (S1) of an n+ silicon substrate (1) having a high impurity concentration to a depth (D), and phosphorus ions (P) are implanted from the surface (S1) to the inside of the n- layer (2E). A SiO2 film is formed on the surface S1 by thermal oxidation, and an opening hole is formed in the SiO2 film. Using the opening hole, p-type impurities are implanted and diffused by thermal oxidation in the ion-implanted n- layer (2E), forming a p-type diffusion layer (well) from the surface (S1) to a predetermined depth. In this way, an n layer is formed in place of the n- layer (2E). The concentration distribution of impurity in the n layer monotonically decreases from the side of the surface (S1) and reaches its minimum on the side of an interface (BS). Then, a predetermined electrode is formed, completing the device. Thus, variations in both on-state resistance and breakdown voltage are reduced in a semiconductor device having a pn junction.

Semiconductor device having a monotonically decreasing impurity concentration

In a semiconductor device having two first conductivity type doped semiconductor layers and a second conductivity type well within the upper more lightly doped layer, the dopant concentration of the more lightly doped layer decreases uniformly from its top surface to a minimum at the interface between the layers. A semiconductor device has (i) first conductivity type doped first and second semiconductor layers (1, 2), the second layer (2) being more lightly doped; (ii) a second conductivity type well (3) extending to a certain depth (d) into the second layer (2); and (c) electrodes (9, 8) respectively on the back face (S1) of the first layer (1) and on the well surface (3S). The dopant concentration of the second layer (2), with the exception of the well (3) is distributed in the depth direction (X1) such that it decreases uniformly from the top surface (S4) of the second layer (2) and reaches a minimum at the interface (BS) between the layers (1, 2). An Independent claim is also included for producing the above semiconductor device, in which the dopant concentration of the epitaxially grown second layer is altered by selective dopant implantation and diffusion only in the second layer to achieve an altered dopant concentration (n) which is less than that (n+) of the first layer but is greater than the original dopant concentration of the second layer.

Junichi Yamashita

Papers

Semiconductor device having a monotonically decreasing impurity concentration

Semiconductor device with a p-n junction