Forming a sacrificial liner for dual channel devices

A semiconductor device, comprising:

• one or more fins, each fin comprising:
• a top channel portion formed from a channel material;
• and
• a bottom substrate portion formed from a same material as an underlying substrate;
• an isolation dielectric layer formed between and around the bottom substrate portion of the one or more fins;
• a single oxide layer formed in direct contact with the bottom substrate portion of each fin, between the bottom substrate portion of each fin and the isolation dielectric layer, wherein a space exists between a straight sidewall of the single oxide layer and a closest fin;
• and
• a gate dielectric formed over the one or more fins and in the space, in contact with both the straight sidewall and the bottom substrate portion.

A semiconductor device, comprising:

• one or more fins, each fin comprising:
• a top channel portion formed from a channel material;
• a bottom substrate portion formed from a same material as an underlying substrate;
• and
• a middle portion formed from a same material as the underlying substrate and having a width that is lower than the width of the bottom substrate portion;
• an isolation dielectric layer formed between and around the bottom substrate portion of the one or more fins;
• a single oxide layer formed in direct contact with the bottom substrate portion of each fin, between the bottom substrate portion of each fin and the isolation dielectric layer;
• and
• a gate dielectric formed over the one or more fins and between a straight sidewall of at least a top portion of the single oxide layer and an adjacent sidewall of the one or more fins, in contact with both the straight sidewall and the bottom substrate portion.