Nec Corporation

Nec Compound Semiconductor Devices, Ltd.

Michihisa Kohno

Shuji Asai

The present invention enables reduction of a film thickness of a protection film so as to eliminate destruction caused by stress of the protection film; to increase a film thickness of an organic insulation film so as to exhibit the function of the organic insulation film sufficiently; and to reduce irregularities of the protection film thickness. In the organic insulation film formation method according to the present invention, an organic insulation film , a protection film , and a metal film are successively formed in this order on a substrate . On the metal film, a patterned photo-resist is formed so as to be used as a mask for etching the metal film. The remaining metal film is used as a mask when etching the protection film and the organic insulation film . The protection film can significantly reduce its thickness because the protection film need not be used as a mask. The organic insulation film can be set to an arbitrary thickness regardless of the protection film

Organic insulation film formation method

On a semi-insulative GaAs substrate, a channel layer, an electron supply layer, a threshold voltage controlling layer, an etching stop layer, a contact layer and an insulation layer are grown. By etching the insulation layer, gate openings are formed in an E-type element region and a D-type element region. With taking the gate opening as mask, dry etching is performed for the contact layer to form openings. On the inner periphery of the openings, side wall insulation layers are formed. With masking the gate opening in the D-type element region, and with taking the side wall insulation layer as mask, the etching stop layer is etched by wet etching, and threshold voltage controlling layer is etched by isotropic dry etching. After formation of the gate electrodes, source and drain electrodes are formed. By this, damaging of crystal upon formation of recess portion by etching is eliminated to prevent degradation of characteristics. Also, a source resistance can be lowered.

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Tokyo, Japan

Michihisa Kohno