**Exhibit12.1**

**Section302 Certification**

I, Paul Hyland certifythat:

1. I have reviewed thisannual report on Form 20-F for the fiscal year ended December 31, 2006 ofAIXTRON Aktiengesellschaft (the “Company”);

2. Based on myknowledge, this report does not contain any untrue statement of a material factor omit to state a material fact necessary to make the statements made, inlight of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

3. Based on myknowledge, the financial statements, and other financial information includedin this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the Company as of, and for,the periods presented in this report;

4. The Company’s othercertifying officer(s) and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e)and 15d-15(e)) and internal controls over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f)) for the Company and have:

(a) Designed suchdisclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the Company, including its consolidated subsidiaries,is made known to us by others within those entities, particularly during theperiod in which this report is being prepared;

(b) Designed suchinternal control over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles;

(c) Evaluated theeffectiveness of the Company’s disclosure controls and procedures and presentedin this report our conclusions about the effectiveness of the disclosurecontrols and procedures, as of the end of the period covered by this reportbased on such evaluation; and

(d) Disclosed in thisreport any change in the Company’s internal control over financial reportingthat occurred during the period covered by the annual report that has materiallyaffected, or is reasonably likely to materially affect, the Company’s internalcontrol over financial reporting; and

5. The Company’s othercertifying officer(s) and I have disclosed, based on our most recent evaluationof internal control over financial reporting, to the Company’s auditors and theAudit Committee of the Company’s board of directors (or persons performing theequivalent functions):

(a) All significantdeficiencies and material weaknesses in the design or operation of internalcontrol over financial reporting which are reasonably likely to adverselyaffect the Company’s ability to record, process, summarize and report financialinformation; and

(b) Any fraud, whetheror not material, that involves management or other employees who have a significantrole in the Company’s internal control over financial reporting.

Date: March 15, 2007

 
| /s/ PAUL HYLAND |                                      |
|----------------------|-------------------------------------------|
| Name:                | **Paul Hyland**                           |   |
| Title:               | **President and Chief Executive Officer** |   |

 

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