Field effect transistor with barrier layer to prevent avalanche breakdown current from reaching gate and method for manufacturing the same

A field effect transistor, comprising:

• a gate electrode;
• a first conductive type channel layer;
• an insulation substrate;
• a first conductive type layer, which is provided between the insulation substrate and the first conductive type channel layer, and which is depleted;
• a second conductive type layer, the first conductive type layer and the second conductive type layer, which are provided between the first conductive type channel layer and the insulation substrate, forming a potential barrier;
• a high impurity concentration layer of a second conductive type, which is formed on the insulation substrate and comprises an impurity concentration of 1019 cm−3 or more;
• and
• an ohmic electrode connected to the high impurity concentration layer of the second conductive type,
• wherein the potential barrier formed by the first conductive type layer and the second conductive type layer serves as a barrier for preventing a second conductive type carrier from flowing out of the insulation substrate in a direction of the gate electrode, even when a large voltage is applied to the gate electrode, the large voltage being larger than a bias voltage required for cutting off a channel of the first conductive type channel layer.

A field effect transistor, comprising:

• a second conductive type substrate;
• a low concentration second conductive type layer formed on and having an impurity concentration lower than the second conductive type substrate;
• a second conductive type layer formed on and having an impurity concentration greater than the low concentration second conductive type layer;
• a first conductive type layer which is depleted and is formed on the second conductive type layer;
• a non-doped layer formed on the first conductive type layer;
• a first conductive type channel layer formed on the non-doped layer;
• a gate electrode formed on the first conductive type channel layer;
• and
• a source electrode and a drain electrode, each formed on high concentration first conductive type layer having an impurity concentration greater than the first conductive type channel layer,
• wherein a potential barrier is formed by the first conductive type layer and the second conductive type layer that prevents a second conductive type carrier flow from the second conductive type substrate to the first conductive type channel layer.