Abstract: A J-FET includes a channel layer of a first conductivity type (a Si-doped n-type AlGaAs electron supply layers 3 and 7, undoped AlGaAs spacer layers 4 and 6, and an undoped InGaAs channel layer 5) formed above a semi-insulating GaAs substrate, an upper semiconductor layer made up of at least one semiconductor layer and formed above the channel layer of the first conductivity type, a semiconductor layer of a second conductivity type (C-doped p+-GaAs layer 18) formed in a recess made in the upper semiconductor layer or formed above the upper semiconductor layer, a gate electrode placed above and in contact with the semiconductor layer of the second conductivity type, and a gate insulating film including a nitride film formed above and in contact with the upper semiconductor layer and an oxide film formed above the nitride film and having a larger thickness than the nitride film.

Abstract: A problem is arisen in conventional J-FETs that a shifting in a threshold voltage (VT) is generated before or after an energization with a gate current. A junction gate field effect transistor (J-FET) according to the present invention includes an undoped InGaAs channel layer 5, which is capable of accumulating carrier of a first conductivity type, a p+ type GaAs layer 17 (semiconductor layer), which is provided on the undoped InGaAs channel layer 5, and contains an impurity of a second conductivity type, and a gate electrode 18, which is provided on the p+ type GaAs layer 17. Here, the concentration of hydrogen contained in the p+ type GaAs layer 17 is lower than the concentration of the second conductivity type carrier in the p+ type GaAs layer 17.

Abstract: A field effect transistor includes a Schottky layer; a stopper layer formed of InGaP and provided in a recess region on the Schottky layer; a cap layer provided on the stopper layer and formed of GaAs; and a barrier rising suppression region configured to suppress rising of a potential barrier due to interface charge between the stopper layer and the cap layer. The cap layer includes a high concentration cap layer; and a low concentration cap layer provided directly or indirectly under the high concentration cap layer and having an impurity concentration lower than the high concentration cap layer.

Abstract: A semiconductor device includes at least one semiconductor element having a semiconductor stack containing a channel layer and a cap layer and a lower electrode and an upper electrode formed over a semiconductor stack, and at least one protective element having the semiconductor stack in common with the semiconductor element for protecting the semiconductor element. The protective element includes a recessed portion that penetrates the cap layer in the direction of the thickness, an insulation region formed in the semiconductor stack from the bottom of the recessed portion 221 in the direction of the thickness, and a pair of ohmic electrodes and formed on both sides of the recessed portion and connected to the cap layer.

Abstract: It is desired for semiconductor devices to reduce leakage currents. In a semiconductor device having a stacked structure including a GaAs layer and an InGaP layer, p-type impurity is doped to the GaAs layer. Consequently, the conduction band of the GaAs is raised to higher than the Fermi level. As a result, electron accumulation is suppressed and the gate leakage current can be reduced.

Abstract: A semiconductor device having first and second stacks formed successively over a common substrate, in which the first stack that remains after removing the second stack comprises a field effect transistor, the second stack that is stacked over the first stack comprises a device different from the field effect transistor, and the first stack comprising the field effect transistor has an etching stopper layer that defines a stopping position of a recess formed in the first stack and comprises InGaP, a lower compound semiconductor layer that is disposed below a gate electrode disposed in the recess and comprises AlGaAs, and a spacer layer that is interposed between the etching stopper layer and the lower compound semiconductor layer for preventing phosphorus contained in the etching stopper layer from thermally diffusing as far as the lower compound semiconductor layer and chemically bonding with constituents elements of the lower compound semiconductor layer.

Abstract: A semiconductor device with a heterojunction bipolar transistor (HBT) and a field effect transistor (FET) formed over the same substrate; providing improved HBT characteristics and a lowered HBT collector resistance and also satisfactory etching of the FET gate recess, along with low ON-resistance in the FET. The sub-collector layer of a heterojunction bipolar transistor (HBT) is a laminated structure of multiple semiconductor layers, and moreover with a collector electrode formed on a section projecting out from one collector layer. In two of the FET, at least one semiconductor layer on the semiconductor substrate side of the semiconductor layers forming the sub-collector layer of the HBT also serves as at least a portion of a capacitor layer. The total film thickness of the HBT sub-collector layer is 500 nm or more; and the total film thickness of the FET capacitor layer is between 50 nm and 300 nm.

Abstract: A semiconductor device includes a substrate common to a first field effect transistor and a second field effect transistor, a channel layer of a first conductivity type formed on the substrate and common to the first and second field effect transistors, a an upper compound semiconductor layer formed on the channel layer and common to the first and second field effect transistors, a compound semiconductor region of a second conductivity type formed in the same layer as the upper compound semiconductor layer, a gate electrode of the first field effect transistor in ohmic contact with the compound semiconductor region, and a gate electrode of the second field effect transistor in Schottky contact with the upper compound semiconductor layer.

Abstract: A semiconductor device includes at least one semiconductor element having a semiconductor stack containing a channel layer and a cap layer and a lower electrode and an upper electrode formed over a semiconductor stack, and at least one protective element having the semiconductor stack in common with the semiconductor element for protecting the semiconductor element. The protective element includes a recessed portion that penetrates the cap layer in the direction of the thickness, an insulation region formed in the semiconductor stack from the bottom of the recessed portion 221 in the direction of the thickness, and a pair of ohmic electrodes and formed on both sides of the recessed portion and connected to the cap layer.

Abstract: A field effect transistor includes a Schottky layer; a stopper layer formed of InGaP and provided in a recess region on the Schottky layer; a cap layer provided on the stopper layer and formed of GaAs; and a barrier rising suppression region configured to suppress rising of a potential barrier due to interface charge between the stopper layer and the cap layer. The cap layer includes a high concentration cap layer, and a low concentration cap layer provided directly or indirectly under the high concentration cap layer and having an impurity concentration lower than the high concentration cap layer.

Abstract: It is desired for semiconductor devices to reduce leakage currents. In a semiconductor device having a stacked structure including a GaAs layer and an InGaP layer, p-type impurity is doped to the GaAs layer. Consequently, the conduction band of the GaAs is raised to higher than the Fermi level. As a result, electron accumulation is suppressed and the gate leakage current can be reduced.

Abstract: A J-FET includes a channel layer of a first conductivity type (a Si-doped n-type AlGaAs electron supply layers 3 and 7, undoped AlGaAs spacer layers 4 and 6, and an undoped InGaAs 5 channel layer 5) formed above a semi-insulating GaAs substrate, an upper semiconductor layer made up of at least one semiconductor layer and formed above the channel layer of the first conductivity type, a semiconductor layer of a second conductivity type (C-doped p+-GaAs layer 18) formed in a recess made in the upper semiconductor layer or formed above the upper semiconductor layer, a gate electrode placed above and in contact with the semiconductor layer of the second conductivity type, and a gate insulating film including a nitride film formed above and in contact with the upper semiconductor layer and an oxide film formed above the nitride film and having a larger thickness than the nitride film.

Abstract: A field effect transistor according to an embodiment of the invention includes: a semiconductor substrate; a channel layer of a first conductivity type formed on the semiconductor substrate; and a semiconductor layer of a second conductivity type that is buried in a recess structure formed in a semiconductor layer on the channel layer and connected with a gate electrode, in which the recess structure is formed using a recess stopper layer containing In, a semiconductor layer that contacts the bottom of the semiconductor layer of the second conductivity type does not contain In, and the uppermost semiconductor layer among semiconductor layers that contact a side surface of the semiconductor layer of the second conductivity type does not contain In.

Abstract: A semiconductor device includes a substrate common to a first field effect transistor and a second field effect transistor, a channel layer of a first conductivity type formed on the substrate and common to the first and second field effect transistors, a an upper compound semiconductor layer formed on the channel layer and common to the first and second field effect transistors, a compound semiconductor region of a second conductivity type formed in the same layer as the upper compound semiconductor layer, a gate electrode of the first field effect transistor in ohmic contact with the compound semiconductor region, and a gate electrode of the second field effect transistor in Schottky contact with the upper compound semiconductor layer.

Abstract: A problem is arisen in conventional J-FETs that a shifting in a threshold voltage (VT) is generated before or after an energization with a gate current. A junction gate field effect transistor (J-FET) according to the present invention includes an undoped InGaAs channel layer 5, which is capable of accumulating carrier of a first conductivity type, a p+ type GaAs layer 17 (semiconductor layer), which is provided on the undoped InGaAs channel layer 5, and contains an impurity of a second conductivity type, and a gate electrode 18, which is provided on the p+ type GaAs layer 17. Here, the concentration of hydrogen contained in the p+ type GaAs layer 17 is lower than the concentration of the second conductivity type carrier in the p+ type GaAs layer 17.

Abstract: A field effect transistor according to an embodiment of the invention includes: a semiconductor substrate; a channel layer of a first conductivity type formed on the semiconductor substrate; and a semiconductor layer of a second conductivity type that is buried in a recess structure formed in a semiconductor layer on the channel layer and connected with a gate electrode, in which the recess structure is formed using a recess stopper layer containing In, a semiconductor layer that contacts the bottom of the semiconductor layer of the second conductivity type does not contain In, and the uppermost semiconductor layer among semiconductor layers that contact a side surface of the semiconductor layer of the second conductivity type does not contain In.

Abstract: In a heterojunction field effect type semiconductor device, a channel layer is formed over a GaAs substrate, and a first semiconductor layer including no aluminum is formed over the channel layer. First and second cap layers of a first conductivity type are formed on the first semiconductor layer, to create a recess on the first semiconductor layer. First and second ohmic electrodes are formed on the first and second cap layers, respectively. A second semiconductor layer of a second conductivity type is formed on the first semiconductor layer within the recess, and the semiconductor layer is isolated from the first and second cap layers. A gate electrode is formed on the second semiconductor layer.

Abstract: In a heterojunction field effect type semiconductor device, a channel layer is formed over a GaAs substrate, and a first semiconductor layer including no aluminum is formed over the channel layer. First and second cap layers of a first conductivity type are formed on the first semiconductor layer, to create a recess on the first semiconductor layer. First and second ohmic electrodes are formed on the first and second cap layers, respectively. A second semiconductor layer of a second conductivity type is formed on the first semiconductor layer within the recess, and the semiconductor layer is isolated from the first and second cap layers. A gate electrode is formed on the second semiconductor layer.

Abstract: An FET (Field Effect Transistor) has an epitaxial wafer including an Al0.2Ga0.8As gate contact layer. A GaAs gate buried layer doped with Si, Al0.2Ga0.8As wide-recess stopper layer doped with Si, an undoped GaAs layer and a GaAs cap layer doped with Si are sequentially formed on the gate contact layer by epitaxial growth. An electron accumulation layer is formed on the undoped GaAs layer and reduces a potential barrier. This allows electrons to pass through the potential barrier of the AlGaAs layer with higher probability. Because the GaAs layer is not doped with an impurity, electrons are scattered little and achieve higher mobility. It is therefore possible to reduce contact resistance from the cap layer to a channel layer. In addition, sheet resistance sparingly increases because the gate contact layer is not exposed to the outside. An ON resistance as low as 1.4 &OHgr;·mm is achievable which is lower than the conventional ON resistance by 0.2 &OHgr;·mm.

Abstract: An FET (Field Effect Transistor) has an epitaxial wafer including an Al0.2Ga0.8As gate contact layer. A GaAs gate buried layer doped with Si, Al0.2Ga0.8As wide-recess stopper layer doped with Si, an undoped GaAs layer and a GaAs cap layer doped with Si are sequentially formed on the gate contact layer by epitaxial growth. An electron accumulation layer is formed on the undoped GaAs layer and reduces a potential barrier. This allows electrons to pass through the potential barrier of the AlGaAs layer with higher probability. Because the GaAs layer is not doped with an impurity, electrons are scattered little and achieve higher mobility. It is therefore possible to reduce contact resistance from the cap layer to a channel layer. In addition, sheet resistance sparingly increases because the gate contact layer is not exposed to the outside. An ON resistance as low as 1.4 &OHgr;·mm is achievable which is lower than the conventional ON resistance by 0.2 &OHgr;·mm.