Semiconductor device with an MOST provided with an extended drain region for high voltages.

摘要

The invention relates to a semiconductor device with a semiconductor body (1) comprising a surface region (3) of a first conductivity type which adjoins a surface and in which a field effect transistor is provided which comprises a channel region (7) with a gate electrode (8) above it, and a source region (4), a drain region (5) and a drain extension region (6). The drain extension region (6) serves to improve the drain breakdown voltage of the field effect transistor. In practice, a high breakdown voltage is accompanied by a comparatively high on-resistance of the transistor. According to the invention, the drain extension region (6) has a geometry different from that in known transistors, i.e. the drain extension region (6) comprises a number of zones (25) of the second conductivity type which extend from the channel region (7) to the drain region (5) and which have a width (26) and doping concentration such that, when the voltage difference across the blocked pn junction (28) between the surface region (3) and the drain extension region (6) is increased, the drain extension region (6) is fully depleted at least locally before drain breakdown occurs. The measure according to the invention renders it possible to choose the number and the width (26) of the zones (25) as an additional parameter of the device. It is a surprise to find that devices according to the invention have comparatively high drain breakdown voltages and comparatively low on-resistances which cannot be realised with a continuous drain extension region (6).