JPS5541730A - Semiconductor device - Google Patents

Abstract

PURPOSE: To reduce the number of diffusion processes in the manufacture of a semiconductor device by providing a second type conductive layer in a first type conductive substrate, then a pair of the first type layers in the second type layer and a same type conductive layer between the two layers, and thus forming a guard diode.

CONSTITUTION: P-type layers 22 and 23 are formed in an n-type substrate 21 by diffusion from the upper surface. An n-type layer 24 is formed in the substrate 21 while n-type layers 25 and 26∼28 are formed in the layers 22 and 23, respectively, either by selective diffusion. A gate electrode 30 is formed on the then prepared gate insulating film; a drain electrode 31 on the layer 24; a source electrode 32 on the layers 22 and 25; and electrodes 33 and 34 on the layer 23. The electrode 33 is connected to the electrode 30, while the electrode 34 to the electrode 32, to form a two-way guard diode between the electrodes 33 and 34, whereby breakdown may occur to a PN junction J₁₁ or J₁₂ when an excessive positive or negative voltage is applied to the electrode 30, so that the gate insulting film is protected from destruction. According to this device, the diffusion processes are performed satisfactorily only twice, and yet the substrate 21 is protected from drop in concentration.

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